−---
−title: Commercial Water Heaters
−category: Plumbing
−toc_depth: 3
−description: >
− When to use: Commercial domestic-hot-water (DHW) generation equipment serving commercial, institutional, and industrial buildings. Covers storage gas-fired water heaters (atmospheric, power-vented, power-direct-vented, and condensing), commercial electric storage water heaters, instantaneous and tankless gas water heaters (including condensing), heat-pump water heaters (HPWH), indirect-fired storage tanks heated by a boiler heat exchanger or by solar / waste-heat sources, and semi-instantaneous packaged units. Includes storage tanks (glass-lined, stainless, cement-lined), thermal expansion tanks, ASSE 1017 master mixing valves and ASSE 1070 point-of-use temperature-limiting devices, recirculation pumps and the circulating system, ASHRAE 188 Legionella requirements (storage and distribution setpoints, mixing-valve setpoints), and the venting, fuel-gas connection, condensate drain, electrical, and seismic provisions associated with the water-heating equipment itself.
−
− Not intended for: Domestic water piping upstream and downstream of the equipment (see [[sync/domestic-water-piping]]); the plumbing fixtures served (see [[sync/plumbing-fixtures]]); sanitary-waste and vent piping for tank, T&P relief, and condensate routing to drain (see [[sync/sanitary-waste-and-vent-piping]]); building water-service backflow prevention assemblies (see [[sync/backflow-prevention]]); solar thermal collectors and solar array piping (separate scope; indirect-fired storage tanks heated by a solar loop are within this scope but the collector array is not); hydronic-heating boilers serving space-heating loops (those serve the building-heating system, not DHW — see [[sync/hydronic-piping]] for the boiler-side hydronic piping, with indirect DHW tank coil connections covered here); pool and spa water heating; process and industrial hot water generation above standard DHW temperatures; steam-to-water DHW heat exchangers in central steam plants (a related but distinct equipment category).
−---
−
−# Scope
−
−This standard covers the equipment, accessories, controls, vent and combustion-air system, fuel-gas piping connection, electrical connection, condensate handling, seismic restraint, installation, startup, and testing of commercial domestic-hot-water generating equipment. The scope of this standard begins at the cold-water inlet connection to the water heater or storage tank and terminates at the hot-water and recirculation-return outlet connections downstream of the master mixing valve. The domestic-water piping that conveys water to and from this equipment is the subject of [[sync/domestic-water-piping]].
−
−All wetted components in contact with potable water shall comply with NSF/ANSI 61 for health effects and NSF/ANSI/CAN 372 for lead-free content (0.25 percent maximum weighted average lead content of wetted surface area), a federal requirement under the Safe Drinking Water Act applicable to all plumbing components installed on or after January 4, 2014.
−
−Equipment selection, capacity, redundancy, location, and the recirculation-system layout are [[drawing: as indicated on the plumbing equipment schedules, mechanical room plans, and water heater piping diagrams]]. This standard establishes the materials, performance, controls, and installation requirements that govern those drawings.
−
−This standard addresses the equipment itself. Building-wide Legionella management is the subject of a project-specific Water Management Program developed in accordance with ASHRAE 188 by the Owner's design team and operations staff; this standard establishes the equipment-level temperature, mixing-valve, and recirculation requirements necessary to support that program but does not constitute the program itself.
−
−# Referenced Standards
−
−Equipment, components, and installation shall comply with the latest adopted edition of the following standards and codes. Where the contract documents, the Authority Having Jurisdiction (AHJ), or a referenced standard impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing. The applicable plumbing code — International Plumbing Code (IPC) or Uniform Plumbing Code (UPC) as adopted by the jurisdiction — the applicable mechanical code, and the applicable fuel-gas code (NFPA 54 / International Fuel Gas Code) shall take precedence over all other references on any matter directly addressed by those codes.
−
−| Standard | Title |
−|----------|-------|
−| ASHRAE 188 | Legionellosis: Risk Management for Building Water Systems |
−| ASHRAE 90.1 | Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings (water heater efficiency, pipe insulation, recirculation controls) |
−| ASHRAE 90.2 | Energy-Efficient Design of Low-Rise Residential Buildings (referenced where residential-style equipment is installed in commercial small projects) |
−| ASHRAE 62.1 | Ventilation and Acceptable Indoor Air Quality (combustion-air and mechanical-room ventilation) |
−| IECC | International Energy Conservation Code (commercial provisions referencing ASHRAE 90.1) |
−| 10 CFR Part 431 | DOE Energy Conservation Standards for Commercial Water Heaters (thermal efficiency, standby loss) |
−| 10 CFR Part 430 | DOE Energy Conservation Standards for Consumer Water Heaters (UEF — applies to residential-grade units) |
−| ANSI Z21.10.1 / CSA 4.1 | Gas Water Heaters — Volume I, Storage Water Heaters with Input Ratings of 75,000 Btu/h and Under |
−| ANSI Z21.10.3 / CSA 4.3 | Gas-Fired Water Heaters for Storage and Instantaneous Water Heaters (commercial; inputs above 75,000 Btu/h, and circulating and instantaneous types) |
−| UL 174 | Household Electric Storage Tank Water Heaters |
−| UL 1453 | Electric Booster and Commercial Storage Tank Water Heaters |
−| UL 1995 / CSA C22.2 No. 236 | Heating and Cooling Equipment (referenced for HPWH packaged units, superseded for new HPWHs by UL 60335-2-40) |
−| UL 60335-2-40 / CSA C22.2 No. 60335-2-40 | Household and Similar Electrical Appliances — Safety — Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers |
−| ASME Boiler and Pressure Vessel Code, Section VIII Division 1 | Rules for Construction of Pressure Vessels (tanks exceeding the commercial threshold) |
−| ASME CSD-1 | Controls and Safety Devices for Automatically Fired Boilers (where applicable to high-input water heaters) |
−| NSF/ANSI 5 | Water Heaters, Hot Water Supply Boilers, and Heat Recovery Equipment (commercial food service and hygiene-sensitive applications) |
−| NSF/ANSI 61 | Drinking Water System Components — Health Effects |
−| NSF/ANSI/CAN 372 | Drinking Water System Components — Lead Content |
−| ASSE 1003 | Performance Requirements for Water Pressure Reducing Valves (referenced for upstream PRV coordination) |
−| ASSE 1017 | Performance Requirements for Temperature Actuated Mixing Valves for Hot Water Distribution Systems (master mixing valve) |
−| ASSE 1070 / ASME A112.1070 / CSA B125.70 | Performance Requirements for Water Temperature Limiting Devices (point-of-use thermostatic) |
−| ASSE 1082 | Performance Requirements for Water Heaters with Integral Temperature Limiting Capability |
−| ANSI Z21.22 / CSA 4.4 | Relief Valves for Hot Water Supply Systems (T&P relief valves) |
−| NFPA 54 / ANSI Z223.1 | National Fuel Gas Code |
−| IFGC | International Fuel Gas Code |
−| NFPA 70 | National Electrical Code |
−| NFPA 31 | Standard for the Installation of Oil-Burning Equipment (where oil-fired) |
−| UL 1738 | Venting Systems for Gas-Burning Appliances, Categories II, III, and IV |
−| UL 103 | Factory-Built Chimneys for Residential Type and Building Heating Appliances (Type B and L vent) |
−| UL 174 | Household Electric Storage Tank Water Heaters |
−| AGA / CSA NGV-1 | Compressed Natural Gas Vehicle Fueling Connection Devices (referenced for fuel-gas connection components where applicable) |
−| ASME A112.4.1 | Water Heater Relief Valve Drain Tubes |
−| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures (seismic restraint) |
−| OSHPD / IAPMO listings | Pre-approved seismic anchorage details for water heaters in high-seismic jurisdictions |
−| IPC | International Plumbing Code |
−| UPC | Uniform Plumbing Code |
−
−# Submittals
−
−## Action Submittals
−
−Contractor shall submit the following for the Engineer's review prior to procurement and installation. Work shall not proceed on any water-heating equipment until the corresponding submittals have been reviewed and returned.
−
−- Product data for each water heater, indicating the manufacturer's model number, fuel type, input rating (Btu/h or kW), storage volume, recovery rate at the specified temperature rise, first-hour rating where applicable, thermal efficiency or UEF, vent category (I, II, III, or IV), permitted vent materials and maximum vent length, electrical characteristics, gas-train pressure range, applicable certification listings (ANSI Z21.10.3, UL 1453, UL 60335-2-40, or other as appropriate), and NSF/ANSI 5 listing where required by the application
−- Product data for storage tanks (indirect-fired, ASME, or supplemental), including tank material and lining (glass-lined, stainless steel Type 316L, cement-lined), insulation R-value, working pressure, T&P relief connection size, anode rod type and replacement access, and applicable certification (ASME Section VIII Div 1 stamp where required, NSF/ANSI 61)
−- Product data for the master mixing valve (ASSE 1017), including body material, paired hot/cold/blend connection sizes, minimum and maximum flow rate at the specified pressure drop, setpoint adjustment range, accuracy, integral isolation and check valves, and union or flanged service connections
−- Product data for any point-of-use temperature-limiting devices (ASSE 1070) coordinated with [[sync/plumbing-fixtures]]
−- Product data for the thermal expansion tank, including pre-charge pressure, acceptance volume, total volume, diaphragm or bladder material (potable PE-X lined or butyl), and NSF/ANSI 61 certification for wetted parts
−- Product data for the hot-water recirculation pump, including flow rate, head, motor data, wetted materials (bronze or stainless steel), NSF/ANSI 61 certification, and control type (time clock, aquastat, demand, or combination)
−- Product data for the T&P relief valve per ANSI Z21.22, including set pressure, set temperature, discharge capacity (Btu/h), and connection size; provide separate documentation for tank T&P relief and any heat-exchanger or system relief valves
−- Combustion-air and venting plan for each gas-fired heater, including vent category, vent material and diameter, total equivalent vent length, termination location and clearances, common venting calculations where multiple heaters share a vent, and condensate drain routing for Category IV (condensing) equipment
−- Fuel-gas connection details, including supply pressure at the heater, gas-train components (manual shutoff, sediment trap / dirt leg, union, regulator if required), pipe sizing verification, and CSST or rigid-pipe details
−- Electrical connection details, including circuit ampacity, overcurrent protection size, disconnect location and rating, equipment grounding and bonding (coordinate with [[sync/grounding-and-bonding]] for electric units), and integration with the building energy-management system or BAS (coordinate with [[sync/building-automation-system]])
−- Heat-pump water heater submittals shall additionally include heating capacity at design ambient conditions, COP at AHRI rating conditions, sound level (sones or dBA at specified distance), refrigerant type and charge, condensate generation rate, and any space cooling or dehumidification effect on the mechanical room
−- Seismic anchorage calculations or pre-approved seismic anchorage details (OSHPD, IAPMO, or equivalent) where required by the project's Seismic Design Category
−- Startup and commissioning checklist and the manufacturer's installation and operation manuals
−- Schematic piping diagram showing the heater(s), storage tanks, mixing valves, expansion tank, recirculation pump and balancing valves, isolation valves, gauges, thermometers, drain valves, and union connections, with valve tags assigned and a flow path traceable through the diagram
−
−```datasheet
−label: Action Submittals Required
−type: checkbox
−options:
− - "Water heater product data with input, recovery, efficiency, vent category"
− - "Storage tank product data with lining, insulation, ASME stamp where required"
− - "Master mixing valve product data (ASSE 1017)"
− - "Point-of-use temperature-limiting device product data (ASSE 1070)"
− - "Thermal expansion tank product data (NSF 61 wetted parts)"
− - "Recirculation pump product data (NSF 61 wetted parts)"
− - "T&P relief valve product data (ANSI Z21.22)"
− - "Combustion-air and venting plan"
− - "Fuel-gas connection details"
− - "Electrical connection details"
− - "HPWH-specific submittals (heating capacity, COP, sound, refrigerant)"
− - "Seismic anchorage calculations or pre-approved details"
− - "Startup / commissioning checklist and O&M manuals"
− - "Schematic piping diagram with valve tagging"
−default: "Water heater product data with input, recovery, efficiency, vent category"
−```
−
−## Closeout Submittals
−
−Contractor shall provide the following at substantial completion before the water-heating system is accepted.
−
−- As-built piping schematic showing actual installed configuration, valve tag locations, gauge and thermometer locations, drain valve locations, and the final routing of vent, gas, electrical, and condensate connections
−- Operation and maintenance (O&M) manuals for the water heater, storage tank, mixing valve, expansion tank, recirculation pump, T&P relief valve, controls, and any auxiliary equipment, with the manufacturer's recommended maintenance intervals tabulated
−- Manufacturer's startup report signed by the manufacturer's authorized service representative or by a technician trained and certified by the manufacturer, indicating that combustion, water-side, and electrical systems were verified per the manufacturer's commissioning procedure
−- Combustion test reports for each gas-fired heater, recording fuel-gas supply pressure (static and dynamic), manifold pressure, CO and CO₂ in the flue gas, stack temperature, and combustion efficiency at high-fire and (where modulating or staged) at the lowest stable fire rate
−- Field test reports for water-side performance — measured recovery rate, measured outlet temperature at the heater, measured outlet temperature downstream of the master mixing valve, measured recirculation return temperature at the heater inlet, and verification that the T&P relief valve and any energy cut-out controls function as specified
−- Water Management Program documentation interface — recorded equipment setpoints, recirculation control schedule, and any operational logs required by the Owner's ASHRAE 188 program
−- Warranty documentation for the water heater, the storage tank, the heat exchanger or anode rod (where covered separately), and all auxiliary equipment
−
−# Quality Assurance
−
−## Installer Qualifications
−
−Water-heating equipment installation shall be performed by personnel licensed in the trade or trades that apply to the equipment installed — plumbing license for water-side piping; mechanical license for venting; fuel-gas license where required by the AHJ for fuel-gas connection; and electrical license for the electrical connection. Where the manufacturer requires a factory-authorized startup, startup and initial commissioning shall be performed by a technician currently certified by the equipment manufacturer; the Contractor shall furnish documentation of current certification before startup begins.
−
−Refrigerant-containing heat-pump water heaters with refrigerant quantities at or above the EPA Section 608 threshold (currently 5 lb for most HFC charges) shall be installed and serviced only by EPA 608-certified technicians. The Contractor shall maintain certification documentation on site.
−
−## Product Listing and Certification
−
−Each water heater shall bear the certification mark of a Nationally Recognized Testing Laboratory (NRTL) recognized by OSHA for the applicable product standard — typically ANSI Z21.10.3 / CSA 4.3 for commercial gas, UL 174 or UL 1453 for electric, and UL 60335-2-40 for HPWH. Storage tanks for which ASME Section VIII Division 1 construction is required shall bear the ASME "U" or "UM" stamp. Where the application requires NSF/ANSI 5 listing (commercial food service, healthcare hot-water washing systems, and similar hygiene-sensitive applications), the equipment shall bear the NSF/ANSI 5 listing mark.
−
−## ASME Pressure Vessel Thresholds
−
−A water-heating vessel is considered a "pressure vessel" subject to ASME Boiler and Pressure Vessel Code Section VIII Division 1 construction and stamping requirements when any one of the following thresholds is exceeded: storage volume greater than 120 gal; input rating greater than 200,000 Btu/h; working pressure greater than 160 psi; or operating temperature greater than 210°F. Equipment selected at or above any of these thresholds shall be ASME-stamped, and the certification documentation shall be included in the closeout submittals. The Engineer shall not specify equipment that exceeds an ASME threshold by a small margin in order to avoid the requirement; ASME construction is appropriate at and above these thresholds and shall be procured accordingly.
−
−## Lead-Free Compliance
−
−All wetted components — heater inlet/outlet fittings, dip tubes, tappings, drain valves, T&P relief valve wetted parts, anode rod connections, mixing valve, expansion tank diaphragm or bladder, recirculation pump wetted parts, gauges, and unions — shall be certified to NSF/ANSI/CAN 372, confirming that the weighted average lead content of the wetted surface area does not exceed 0.25 percent. This is a federal requirement under the Reduction of Lead in Drinking Water Act and is not subject to project-level waiver.
−
−## Manufacturer Authorization
−
−Equipment shall be procured through a manufacturer-authorized distributor or representative. The Owner shall not be required to engage a non-authorized rebuilder, refurbisher, or third party for warranty service during the warranty period. The Contractor shall furnish the local authorized service representative's contact information in the O&M manuals.
−
−# Environmental and Service Conditions
−
−## Installation Environment
−
−Water heaters shall be located in a conditioned mechanical space sized to provide combustion air, ventilation, equipment service clearance, and seismic anchorage as required by the equipment listing and by NFPA 54 / IFGC for fuel-fired equipment. The space shall not be subject to freezing temperatures during normal building operation; freeze protection shall be provided where freezing is possible, particularly for condensing equipment with condensate piping. The space shall have a floor drain capable of accepting the maximum flow of the T&P relief valve discharge, condensate discharge, and tank drain-down without flooding adjacent areas. Where a floor drain is not available, an indirect-waste receptor or an alarmed and pumped condensate-collection sump shall be provided.
−
−Heat-pump water heaters introduce a cooling and dehumidification effect on the space they draw air from. The mechanical space shall be sized and ventilated to allow the HPWH to operate without driving space temperature below the manufacturer's minimum operating ambient temperature. Where the heat-pump cooling effect would over-cool the mechanical space during the cooling season, ductwork shall be installed to draw air from a thermally suitable source and return it to a location that does not adversely affect adjacent occupied spaces.
−
−```datasheet
−label: Mechanical Room Floor Drain
−type: radio
−options:
− - "Yes — floor drain provided in mechanical room"
− - "No — indirect waste receptor or condensate sump provided"
−default: "Yes — floor drain provided in mechanical room"
−```
−
−## Combustion Air
−
−Fuel-fired water heaters require combustion air at a rate determined by the input rating of the heater and the venting category. For Category I and II atmospheric and natural-draft heaters, combustion air shall be supplied per NFPA 54 / IFGC by openings communicating with the outside, by an engineered combustion-air duct, or by an interlocked mechanical combustion-air system. For Category III and IV power-vented and direct-vented heaters, combustion air shall be drawn through a sealed combustion-air pipe terminated outside the building in accordance with the manufacturer's vent termination requirements.
−
−```datasheet
−label: Combustion Air Source
−type: select
−options:
− - "Direct-vent (sealed combustion) — concentric or parallel pipe from outside"
− - "Power-vent with indoor combustion air per NFPA 54 openings"
− - "Atmospheric / natural-draft with indoor combustion air per NFPA 54 openings"
− - "Engineered combustion-air duct with interlocked supply fan"
− - "Not applicable — electric or heat-pump (no combustion)"
−default: "Direct-vent (sealed combustion) — concentric or parallel pipe from outside"
−```
−
−## Service Clearances
−
−Service clearances shall meet or exceed the manufacturer's published minimums and the working clearances required by NFPA 70 for the electrical disconnect. Tank-type heaters shall provide overhead access for anode rod replacement equal to the rod length plus a working margin (typically 36 in. above the tank for full-length rods, or as published by the manufacturer for flexible / segmented rods). Direct-vent terminations shall meet the manufacturer's clearance to building openings, soffits, grade, snow line, and adjacent terminations.
−
−## Water Quality
−
−Domestic-water inlet water quality affects the service life of all wetted components, particularly anode rods, glass-lined tank linings, and brazed-plate heat exchangers in indirect-fired equipment. Where the inlet water hardness exceeds 7 grains per gallon (gpg), softening or scale-control treatment shall be evaluated by the Engineer. Where the chloride level exceeds 100 mg/L or the water is supplied by an on-site well of unknown chemistry, the tank lining material shall be selected for the water chemistry (stainless steel 316L for high chlorides; glass-lined for typical municipal supply; cement-lined for very large indirect tanks). The Contractor shall not be responsible for premature equipment failure caused by water chemistry outside the manufacturer's published acceptable range, provided the equipment was installed and started up correctly.
−
−```datasheet
−label: Inlet Water Treatment
−type: select
−options:
− - "None — municipal supply within manufacturer's acceptable range"
− - "Water softener upstream of cold-water inlet"
− - "Scale-control system (template-assisted crystallization or equivalent)"
− - "Engineered treatment per project water analysis"
−default: "None — municipal supply within manufacturer's acceptable range"
−```
−
−# Water Heater Selection
−
−## General Selection Criteria
−
−Water heater type shall be selected to suit the building's hot-water load profile (peak, recovery, and standby), the available utility services (gas service pressure and electric service capacity), the climate (which affects HPWH performance and condensate management), the available mechanical room space, the noise sensitivity of adjacent spaces, the redundancy requirement, and the project's energy and emissions goals. The Engineer shall size the equipment based on the calculated hot-water demand using ASHRAE Handbook procedures or an equivalent recognized method; this standard establishes the equipment performance requirements that govern after the selection is made.
−
−Storage gas-fired heaters are the established standard for commercial DHW in buildings with significant peak-to-average load ratios. Instantaneous (tankless) gas heaters minimize standby loss and footprint and are well suited to applications with steady moderate load or to point-of-use service. Heat-pump water heaters offer high efficiency (COP typically 2 to 4) and electrification but require careful mechanical-room sizing and condensate management. Indirect-fired storage tanks are appropriate where a boiler plant already exists for space heating, deferring the boiler's summer shutdown and providing a domestic-water load. Semi-instantaneous packaged units integrate a small buffer tank with a tankless heat exchanger to provide stable outlet temperature with limited standby loss.
−
−```datasheet
−label: Water Heater Type
−type: radio
−options:
− - "Gas-fired storage — atmospheric (Category I)"
− - "Gas-fired storage — power-vented (Category III)"
− - "Gas-fired storage — power direct-vented (Category III, sealed combustion)"
− - "Gas-fired storage — condensing (Category IV)"
− - "Electric storage — commercial (UL 1453)"
− - "Gas-fired instantaneous / tankless — condensing"
− - "Gas-fired instantaneous / tankless — non-condensing"
− - "Heat-pump water heater (HPWH)"
− - "Indirect-fired storage tank — heated by external boiler"
− - "Indirect-fired storage tank — heated by solar / waste-heat source"
− - "Semi-instantaneous packaged water heater"
−default: "Gas-fired storage — condensing (Category IV)"
−```
−
−## Input Rating
−
−Input rating shall be sized by the Engineer to satisfy the peak hot-water demand in combination with the storage volume. The input rating governs the recovery capacity and the standby losses of the equipment. The input rating shall be [[drawing: as indicated on the water heater schedule]]. The datasheet below establishes the typical input rating ranges; the Engineer's calculation governs the actual selected value.
−
−```datasheet
−label: Heater Input Rating — Gas
−type: range
−unit: Btu/h
−drawing_ref: true
−options:
− min: 75000
− max: 4000000
− setpoints: [75000, 100000, 199000, 300000, 500000, 750000, 1000000, 1500000, 2000000, 3000000, 4000000]
−default: 500000
−```
−
−```datasheet
−label: Heater Input Rating — Electric
−type: range
−unit: kW
−drawing_ref: true
−options:
− min: 6
− max: 180
− setpoints: [6, 9, 12, 18, 24, 36, 54, 72, 90, 120, 150, 180]
−default: 36
−```
−
−## Recovery Capacity
−
−Recovery capacity shall be expressed at a standard temperature rise (ΔT) and shall be sufficient, in combination with the storage volume, to satisfy the peak draw without exceeding the allowable temperature drop at the most remote fixture. Recovery at 100°F rise is the standard reference condition for commercial gas-fired equipment in the U.S. market; recovery at the project-specific design ΔT shall be confirmed against the equipment manufacturer's published performance curves.
−
−```datasheet
−label: Recovery at 100°F ΔT
−type: range
−unit: GPH
−drawing_ref: true
−options:
− min: 30
− max: 5000
− setpoints: [30, 50, 100, 200, 350, 500, 750, 1000, 1500, 2000, 3000, 5000]
−default: 500
−```
−
−## Storage Volume
−
−Storage volume shall be sized to absorb the difference between peak demand and recovery capacity, with a margin sufficient to maintain delivery temperature at the most remote fixture during the design draw. Increasing the storage volume reduces the required input rating; the Engineer shall optimize the storage-to-input ratio based on the load profile, the energy cost, the available space, and ASME-threshold considerations.
−
−```datasheet
−label: Storage Volume
−type: range
−unit: gal
−drawing_ref: true
−options:
− min: 0
− max: 5000
− setpoints: [0, 6, 19, 40, 50, 75, 80, 100, 119, 120, 175, 250, 350, 500, 750, 1000, 1500, 2500, 5000]
−default: 119
−```
−
−Tank-type heaters and supplemental storage tanks at 119 gal nominal and below are commonly selected to remain below the 120-gal ASME threshold; this is a legitimate design choice but shall not be used as a reason to under-size storage where the load profile genuinely calls for a larger tank. Tanks at 120 gal nominal and above shall be ASME-stamped per the threshold criteria in this standard.
−
−## Efficiency
−
−All water heaters shall meet or exceed the applicable minimum efficiency requirement under ASHRAE 90.1, the IECC, and the DOE Energy Conservation Standards (10 CFR Part 431 for commercial; 10 CFR Part 430 for residential-grade units installed in commercial small projects). Performance shall be reported as Uniform Energy Factor (UEF) for residential-grade equipment within DOE scope and as Thermal Efficiency (Et) and Standby Loss (SL) for commercial equipment within DOE scope. The Engineer shall verify that the specified equipment satisfies the federal floor and any state or local energy-code-amended requirement.
−
−```datasheet
−label: Minimum Efficiency Basis
−type: select
−options:
− - "Uniform Energy Factor (UEF) per DOE 10 CFR Part 430 (residential-grade)"
− - "Thermal Efficiency (Et) and Standby Loss (SL) per DOE 10 CFR Part 431 (commercial)"
− - "Coefficient of Performance (COP) at AHRI rating conditions (HPWH)"
−default: "Thermal Efficiency (Et) and Standby Loss (SL) per DOE 10 CFR Part 431 (commercial)"
−```
−
−```datasheet
−label: Minimum Thermal Efficiency — Gas-Fired (Et)
−type: range
−unit: "%"
−options:
− min: 80
− max: 99
− setpoints: [80, 82, 90, 92, 94, 95, 96, 97, 98, 99]
−default: 94
−```
−
−```datasheet
−label: Minimum UEF — Residential-Grade (where applicable)
−type: range
−unit: ""
−options:
− min: 0.60
− max: 4.00
− step: 0.01
−default: 0.81
−```
−
−```datasheet
−label: Minimum HPWH COP at AHRI Conditions (where applicable)
−type: range
−unit: ""
−options:
− min: 2.0
− max: 5.0
− step: 0.1
−default: 3.0
−```
−
−# Storage Tanks
−
−## Tank Construction and Lining
−
−Storage tanks shall be selected with a lining material suitable for the inlet water chemistry, the operating temperature, and the service life expected for the application. Glass-lined steel is the established standard for typical municipal water at storage temperatures up to 180°F; the porcelain-enamel lining is durable but is dependent on a functioning sacrificial anode rod for cathodic protection of the steel substrate at any small lining imperfection. Stainless steel Type 316L tanks eliminate the anode rod and tolerate higher chloride water chemistries; they are appropriate for water with chlorides above 100 mg/L, for installations where anode-rod maintenance is not feasible, and for hygiene-sensitive applications. Cement-lined tanks are used for very large indirect tanks and for raw or untreated water service, and rely on the cement lining's high pH to passivate the steel; cement-lined tanks shall not be drained and left empty for extended periods, which causes the lining to dry and crack.
−
−```datasheet
−label: Storage Tank Lining
−type: select
−options:
− - "Glass-lined steel with sacrificial anode rod (standard)"
− - "Stainless steel Type 316L (no anode required)"
− - "Cement-lined steel (very large indirect tanks, raw water service)"
− - "Integral to packaged heater — manufacturer's standard lining"
−default: "Glass-lined steel with sacrificial anode rod (standard)"
−```
−
−## Anode Rod
−
−Glass-lined tanks shall be provided with at least one sacrificial anode rod, accessible from the top of the tank, of magnesium, aluminum-zinc, or powered-impressed-current type. Magnesium anodes are the standard for typical municipal water and provide strong cathodic protection at the cost of faster consumption and occasional sulfate-reducing-bacteria odor in low-flow installations. Aluminum-zinc anodes are appropriate where magnesium produces "rotten egg" odor or where water hardness is low. Powered-impressed-current anode systems eliminate sacrificial-anode replacement at the cost of a powered control unit and are appropriate for inaccessible installations.
−
−```datasheet
−label: Anode Rod Type
−type: select
−options:
− - "Magnesium — sacrificial (standard for municipal water)"
− - "Aluminum-zinc — sacrificial (where magnesium produces odor)"
− - "Powered impressed-current — non-sacrificial"
− - "Not applicable — stainless steel or cement-lined tank"
−default: "Magnesium — sacrificial (standard for municipal water)"
−```
−
−Anode rods shall be accessible for inspection and replacement without disturbing the surrounding piping; the Contractor shall confirm the overhead clearance required for the rod length and shall locate the tank accordingly. Where overhead clearance is restricted, flexible or segmented anode rods rated by the manufacturer for the application shall be specified.
−
−## Tank Insulation
−
−Tanks shall be factory-insulated with rigid foam, fiberglass, or equivalent to satisfy the standby-loss requirement under DOE 10 CFR Part 431 and ASHRAE 90.1. Field-applied insulation on the tank exterior is not a substitute for factory insulation. Where the tank is located in an unconditioned space and the factory insulation is at the federal minimum, supplemental field-applied insulation per the Engineer's direction may be provided.
−
−```datasheet
−label: Tank Insulation
−type: select
−options:
− - "Factory insulated, R-value meeting ASHRAE 90.1 / DOE minimum"
− - "Factory insulated, R-value exceeding ASHRAE 90.1 by 25 percent or more"
− - "Field-applied supplemental insulation in addition to factory insulation"
−default: "Factory insulated, R-value meeting ASHRAE 90.1 / DOE minimum"
−```
−
−## Indirect-Fired Tank Coil
−
−Indirect-fired storage tanks shall include an internal heat-exchanger coil sized for the design heating load at the boiler-supply temperature provided by the [[sync/hydronic-piping]] boiler loop. The coil material shall be stainless steel or copper, sized for the boiler-side flow rate, and provided with a separate isolation valve and union on both supply and return connections to permit coil replacement. The boiler loop and the domestic water in the tank shall be physically separated by the coil wall; double-wall construction shall be provided where the boiler loop contains glycol or chemical treatment, where required by code, or where the AHJ requires separation between potable water and a chemically treated fluid.
−
−```datasheet
−label: Indirect Tank Coil Wall
−type: radio
−options:
− - "Single-wall coil — boiler loop contains water only (no glycol or chemicals)"
− - "Double-wall coil — boiler loop contains glycol or chemical treatment"
− - "Not applicable — not indirect-fired"
−default: "Not applicable — not indirect-fired"
−```
−
−# Venting and Combustion
−
−## Vent Category
−
−Gas-fired water heaters are classified by venting category under ANSI Z21.10.3 and NFPA 54 by combustion-system pressure (positive or negative within the vent) and by the dew point of the flue gas (above or below). Category I is non-positive vent pressure, non-condensing — typical atmospheric heaters using Type B vent. Category II is non-positive vent pressure, condensing — uncommon. Category III is positive vent pressure, non-condensing — power-vented non-condensing heaters using special vent material rated for positive pressure. Category IV is positive vent pressure, condensing — condensing heaters using AL29-4C stainless steel, polypropylene, or PVC/CPVC vent piping as listed by the manufacturer.
−
−```datasheet
−label: Vent Category
−type: select
−options:
− - "Category I — non-positive, non-condensing (atmospheric, Type B vent)"
− - "Category II — non-positive, condensing (uncommon)"
− - "Category III — positive, non-condensing (power-vented)"
− - "Category IV — positive, condensing"
− - "Not applicable — electric, HPWH, or indirect-fired"
−default: "Category IV — positive, condensing"
−```
−
−## Vent Material
−
−Vent material shall be selected to match the equipment's vent category, to be listed by the equipment manufacturer for the specific model, and to comply with UL 1738 (Categories II, III, IV) or UL 103 (Type B and L vent for Category I). PVC and CPVC vent material is permitted only where specifically listed by the equipment manufacturer and where allowed by the applicable code and AHJ; some jurisdictions and many model codes are moving away from PVC vent for gas-fired condensing appliances due to long-term durability and flue-gas temperature concerns. AL29-4C stainless steel and listed polypropylene are the durable choices for Category IV vent and shall be specified where life-cycle, code, or AHJ considerations warrant.
−
−```datasheet
−label: Vent Material
−type: select
−options:
− - "Type B double-wall metal (Category I only)"
− - "AL29-4C stainless steel (Category III and IV)"
− - "Polypropylene — UL 1738 listed (Category III and IV)"
− - "PVC — manufacturer-listed and AHJ-accepted (Category IV only)"
− - "CPVC — manufacturer-listed and AHJ-accepted (Category IV only)"
− - "Not applicable — electric, HPWH, or indirect-fired"
−default: "AL29-4C stainless steel (Category III and IV)"
−```
−
−## Vent Sizing and Termination
−
−Vent diameter, total equivalent length, number and type of fittings, and termination clearances shall comply with the equipment manufacturer's installation instructions and with NFPA 54 / IFGC. Termination location and configuration are [[drawing: as indicated on the venting plan and mechanical roof plan]]. Common venting of multiple appliances shall be sized using NFPA 54 vent tables or by an engineered sizing method published by the vent or appliance manufacturer; common venting of Category IV equipment from different manufacturers shall not be performed without each manufacturer's written approval of the proposed configuration.
−
−```datasheet
−label: Venting Configuration
−type: radio
−options:
− - "Individually vented — one heater per vent"
− - "Common vented — multiple heaters of same manufacturer per NFPA 54"
− - "Direct-vent through wall — sealed combustion"
− - "Sidewall power vent — non-condensing"
−```
−
−## Condensate Drain (Category IV)
−
−Category IV (condensing) heaters produce acidic condensate (typical pH 3 to 5) that shall be neutralized before discharge to a sanitary drain that may contain ferrous piping, copper piping, or building materials sensitive to acidic discharge. The Contractor shall provide a manufacturer-listed or third-party condensate neutralizer with replaceable limestone or magnesium-oxide media, sized for the maximum condensate flow rate, and shall pipe the neutralizer discharge by gravity or by an approved condensate pump to an indirect-waste receptor or floor drain per the applicable plumbing code. Condensate piping shall be of a material chemically resistant to low-pH condensate — PVC, CPVC, polypropylene, or stainless steel — and shall not be of bare copper, brass, or carbon steel.
−
−```datasheet
−label: Condensate Handling — Category IV
−type: select
−options:
− - "Neutralizer + gravity drain to indirect-waste receptor"
− - "Neutralizer + condensate pump to indirect-waste receptor"
− - "Neutralizer + gravity drain to floor drain"
− - "Not applicable — non-condensing equipment"
−default: "Neutralizer + gravity drain to indirect-waste receptor"
−```
−
−# Fuel-Gas Connection
−
−Fuel-gas piping to the heater shall be sized and installed per NFPA 54 / IFGC and shall comply with [[sync/fuel-gas-piping]] where that standard exists in the library. Each heater shall be provided with a manual gas shutoff valve external to the heater jacket and within sight of the heater; a sediment trap (dirt leg) downstream of the shutoff and immediately upstream of the heater inlet; a union or dielectric flange between the shutoff valve and the heater for service disconnection; and a pressure gauge tap or test port for combustion startup. Where the heater requires a supply pressure different from the building's distribution pressure, an in-line gas pressure regulator listed for the application shall be provided and vented per code.
−
−```datasheet
−label: Fuel-Gas Service to Heater
−type: select
−options:
− - "Natural gas, low-pressure (≤ 0.5 psig at heater)"
− - "Natural gas, elevated pressure with at-heater regulator (2 psig and above)"
− - "Propane (LP), low-pressure (≤ 0.5 psig at heater)"
− - "Propane (LP), elevated pressure with at-heater regulator"
− - "Not applicable — electric, HPWH, or indirect-fired"
−default: "Natural gas, low-pressure (≤ 0.5 psig at heater)"
−```
−
−# Electrical Connection
−
−Electric storage water heaters, heat-pump water heaters, controls for gas-fired heaters, power-vent fans, condensate pumps, and the recirculation pump shall be connected per NFPA 70. Each piece of equipment shall be provided with a disconnect within sight of the equipment per NEC Article 422 (appliances) or Article 430 (motors) as applicable. Equipment grounding and bonding for electric storage water heaters and HPWHs shall comply with [[sync/grounding-and-bonding]]. Branch-circuit conductor sizing, overcurrent protection, and the disconnect rating shall be coordinated with the equipment nameplate values and shall be [[drawing: as indicated on the electrical plans and panelboard schedules]].
−
−```datasheet
−label: Disconnect Type
−type: select
−options:
− - "Non-fused safety switch within sight of equipment"
− - "Fused safety switch within sight of equipment"
− - "Circuit breaker in panelboard within sight of equipment (where permitted)"
− - "Cord and plug connection (where permitted by code and listing)"
−default: "Non-fused safety switch within sight of equipment"
−```
−
−# Heat-Pump Water Heaters
−
−Heat-pump water heaters (HPWHs) extract heat from ambient air and reject it into the stored water, achieving COP values of approximately 2 to 4 depending on ambient conditions. HPWHs introduce specific design considerations: the source-air space must be sized large enough to avoid driving the supply ambient below the unit's minimum operating temperature; condensate is generated by dehumidification of the source air and shall be piped to a drain; sound levels are higher than for resistance electric or gas-fired storage equipment and shall be evaluated against adjacent occupied spaces; and refrigerant safety per UL 60335-2-40 governs the maximum allowable refrigerant charge for the installation environment, particularly for units using A2L refrigerants.
−
−```datasheet
−label: HPWH Source-Air Configuration
−type: select
−options:
− - "Ambient air drawn from mechanical room (room must be sized adequately)"
− - "Ducted from outside — supply and return ducts"
− - "Ducted from outside — supply duct only with mechanical-room exhaust"
− - "Split-system with outdoor compressor and indoor storage tank"
− - "Not applicable — not HPWH"
−default: "Ambient air drawn from mechanical room (room must be sized adequately)"
−```
−
−```datasheet
−label: HPWH Backup Heat Source
−type: select
−options:
− - "Integral electric-resistance backup (factory-installed)"
− - "No backup — HPWH only, sized for full load"
− - "Separate backup heater piped in series or parallel"
− - "Not applicable — not HPWH"
−default: "Integral electric-resistance backup (factory-installed)"
−```
−
−```datasheet
−label: HPWH Maximum Sound Level at 3 ft
−type: range
−unit: dBA
−options:
− min: 40
− max: 75
− step: 1
−default: 55
−```
−
−# Temperature Setpoints and Legionella Control
−
−## Storage Temperature
−
−Storage temperature shall be set in accordance with ASHRAE 188 to inhibit Legionella pneumophila multiplication. Legionella grows in the range of approximately 68°F to 122°F; storing water above 140°F provides reliable thermal disinfection of the storage volume, and storing above 122°F substantially reduces growth. Storage at 140°F or above is the standard recommendation for ASHRAE 188 compliance; healthcare facilities subject to NFPA 99 and applicable state health department requirements typically require storage at 140°F or higher with documented operational temperature logging.
−
−```datasheet
−label: Storage Temperature Setpoint
−type: select
−unit: °F
−options:
− - "140°F — ASHRAE 188 standard"
− - "135°F — ASHRAE 188 acceptable (lower limit of recommended range)"
− - "150°F — enhanced thermal disinfection (healthcare common)"
− - "160°F — high-temperature pasteurization service"
−default: "140°F — ASHRAE 188 standard"
−```
−
−## Distribution Temperature
−
−Distribution temperature downstream of the master mixing valve shall be maintained at or above 120°F to keep the entire recirculation loop above the Legionella growth range while delivering water at a temperature that does not require fixture-level scald protection beyond the point-of-use temperature-limiting devices specified in [[sync/plumbing-fixtures]]. Distribution at lower temperatures may be approved where every fixture is served by an ASSE 1070 point-of-use device set to deliver water at the fixture, and where the recirculation return temperature is documented to remain above 110°F under all operating conditions.
−
−```datasheet
−label: Distribution Temperature Setpoint (Mixing Valve Outlet)
−type: select
−unit: °F
−options:
− - "120°F — ASHRAE 188 standard"
− - "124°F — enhanced Legionella control"
− - "115°F — only where every fixture has ASSE 1070 point-of-use control"
−default: "120°F — ASHRAE 188 standard"
−```
−
−## Master Mixing Valve
−
−A master mixing valve conforming to ASSE 1017 shall be installed immediately downstream of the water heater(s) or supplemental storage to blend stored water (140°F or higher) with cold water to deliver the distribution setpoint (typically 120°F) to the building. The mixing valve shall be selected with a turndown ratio sufficient to maintain accurate outlet temperature at the minimum recirculation flow rate during low-demand periods, and shall not be undersized such that the minimum draw exceeds its low-flow accuracy band. Where the minimum flow exceeds the maximum capacity of a single ASSE 1017 valve, multiple valves shall be piped in parallel with isolation valves to permit one valve to operate during low demand and additional valves to bring online as flow increases.
−
−```datasheet
−label: Master Mixing Valve — ASSE 1017
−type: select
−options:
− - "Single ASSE 1017 valve sized for the design flow range"
− - "Parallel ASSE 1017 valves with sequenced isolation for wide turndown"
− - "ASSE 1017 with digital electronic mixing control and sensor feedback"
−default: "Single ASSE 1017 valve sized for the design flow range"
−```
−
−```datasheet
−label: Master Mixing Valve — Body Material
−type: radio
−options:
− - "Bronze body, brass trim, NSF 61/372"
− - "Stainless steel body, NSF 61/372"
−default: "Bronze body, brass trim, NSF 61/372"
−```
−
−## Point-of-Use Temperature Limiting
−
−Fixtures requiring delivery temperature below the distribution setpoint — public lavatories, handwash stations, showers in any application, and any fixture in a school or healthcare facility — shall be served by an ASSE 1070 point-of-use temperature-limiting device installed at the fixture or fixture group. Showers shall also be served by an ASSE 1016 anti-scald shower valve in addition to or in lieu of the ASSE 1070 device per the requirements of [[sync/plumbing-fixtures]].
−
−```datasheet
−label: Point-of-Use Temperature-Limiting Coverage
−type: radio
−options:
− - "All public lavatories, handwash stations, showers, and school/healthcare fixtures"
− - "Only fixtures where required by code (typical commercial baseline)"
− - "Project-specific scope per [[sync/plumbing-fixtures]]"
−default: "All public lavatories, handwash stations, showers, and school/healthcare fixtures"
−```
−
−# Thermal Expansion Tank
−
−A thermal expansion tank shall be installed on the cold-water inlet side of the water heater whenever the building is served through a backflow-preventing device — a reduced-pressure principle backflow assembly, a double-check valve, a pressure-reducing valve, or a check valve — that creates a closed system. In a closed system, the expansion of water when heated cannot return upstream to the utility main, so without an expansion tank the system pressure can rise to the T&P relief valve set pressure and cause repeated relief discharge, eventually compromising the relief valve seat. The expansion tank shall be sized using the manufacturer's published method based on the storage volume, the temperature rise from cold-water supply to setpoint, and the system supply pressure.
−
−```datasheet
−label: Thermal Expansion Tank
−type: radio
−options:
− - "Required — closed system (backflow preventer, PRV, or check valve present)"
− - "Not required — open system (no upstream check or backflow device)"
−default: "Required — closed system (backflow preventer, PRV, or check valve present)"
−```
−
−```datasheet
−label: Expansion Tank Diaphragm / Bladder Material
−type: radio
−options:
− - "Potable PE-X (cross-linked polyethylene) lined bladder, NSF 61"
− - "Butyl rubber bladder, NSF 61"
−default: "Potable PE-X (cross-linked polyethylene) lined bladder, NSF 61"
−```
−
−```datasheet
−label: Expansion Tank Acceptance Volume
−type: range
−unit: gal
−drawing_ref: true
−options:
− min: 1
− max: 80
− setpoints: [1, 2, 4.4, 8.5, 14, 20, 32, 44, 62, 80]
−default: 4.4
−```
−
−The expansion tank pre-charge pressure shall be set equal to the system static pressure at the expansion tank's installed elevation before the tank is connected to the water side of the system. Pre-charge pressure adjustment after connection requires draining the system side of the tank and is service-intensive; the Contractor shall measure system static pressure and adjust pre-charge before installation, not after.
−
−# Pressure and Temperature Relief
−
−Each storage water heater and each indirect storage tank shall be provided with a combined temperature and pressure (T&P) relief valve conforming to ANSI Z21.22 / CSA 4.4, listed for the heater's input rating in Btu/h and the tank's working pressure in psi. The relief valve shall be installed in a dedicated tapping at the top of the tank or at the location specified by the manufacturer's instructions; it shall not be valved off, and the inlet shall not be reduced in size. The discharge from the T&P relief valve shall be piped full-size by gravity to a safe location of discharge — a floor drain or an indirect-waste receptor — such that any discharge is visible to building maintenance personnel and any thermal hazard is minimized. Discharge piping shall be of a material rated for the relief temperature (typically 210°F) and shall terminate with an air gap above the receptor.
−
−```datasheet
−label: T&P Relief Valve Set Pressure
−type: select
−unit: psi
−options:
− - "75 psi"
− - "100 psi"
− - "125 psi"
− - "150 psi"
−default: "150 psi"
−```
−
−```datasheet
−label: T&P Relief Valve Set Temperature
−type: radio
−unit: °F
−options:
− - "210°F (standard)"
−default: "210°F (standard)"
−```
−
−```datasheet
−label: T&P Relief Discharge Piping
−type: select
−options:
− - "Copper Type L, full-size, to indirect-waste receptor with air gap"
− - "CPVC ASTM D2846, full-size, to indirect-waste receptor with air gap"
− - "Galvanized steel, full-size, to indirect-waste receptor with air gap"
−default: "Copper Type L, full-size, to indirect-waste receptor with air gap"
−```
−
−# Recirculation System
−
−## Purpose
−
−In commercial buildings, domestic hot water must be delivered to fixtures within a time that satisfies both occupant comfort and the energy code. Without a recirculation system, water in long horizontal branches stagnates, cools, and creates conditions favorable to Legionella in the dead leg. The recirculation system keeps water circulating continuously or on a controlled schedule through a return loop from the distribution piping back to the water heater (or back into the cold-water inlet upstream of the heater, depending on the recirculation strategy), maintaining the return temperature above the Legionella threshold throughout the loop. The return-loop piping itself is the scope of [[sync/domestic-water-piping]]; this standard establishes the pump, control, and balancing requirements at the equipment.
−
−```datasheet
−label: Recirculation System Configuration
−type: select
−options:
− - "Pumped return to water heater inlet (standard)"
− - "Pumped return to a dedicated heater recirculation port"
− - "Pumped return to a recirculation tee on the cold-water inlet (uncommon)"
− - "Demand recirculation with point-of-use trigger"
− - "Not applicable — no recirculation required (small system)"
−default: "Pumped return to water heater inlet (standard)"
−```
−
−## Recirculation Pump
−
−The recirculation pump shall be an in-line centrifugal pump with bronze or stainless steel wetted parts, NSF/ANSI 61 certified, sized for the recirculation flow rate and head loss determined by the Engineer. The pump shall be installed with isolation valves on suction and discharge, a check valve on the discharge, unions for service removal, and a strainer on the suction where required by the manufacturer. The pump motor shall be permanently lubricated, totally enclosed fan-cooled (TEFC) or open-drip-proof (ODP) as suitable for the mechanical-room environment, and rated for continuous duty at the design flow.
−
−```datasheet
−label: Recirculation Pump Wetted Material
−type: radio
−options:
− - "Bronze body and impeller (standard)"
− - "Stainless steel body and impeller (aggressive water)"
−default: "Bronze body and impeller (standard)"
−```
−
−```datasheet
−label: Recirculation Pump Motor
−type: select
−options:
− - "Wet-rotor permanent-magnet ECM (variable-speed, energy-efficient)"
− - "Wet-rotor fixed-speed (standard)"
− - "Inline centrifugal with separate motor"
−default: "Wet-rotor permanent-magnet ECM (variable-speed, energy-efficient)"
−```
−
−## Recirculation Control
−
−ASHRAE 90.1 requires that recirculation pumps not operate continuously when there is no demand. Control shall be by aquastat (return temperature sensor), time clock, demand-based trigger, or a combination, as required by the energy code in force and the building's operating schedule. Combined aquastat-plus-time-clock control is the most common commercial configuration — the time clock disables the pump during unoccupied hours, and the aquastat cycles the pump within occupied hours to maintain return temperature only when needed.
−
−```datasheet
−label: Recirculation Pump Control
−type: select
−options:
− - "Aquastat + time clock combination (standard)"
− - "Aquastat only (continuous-occupied applications)"
− - "Time clock only (legacy; not preferred for new construction)"
− - "Demand-based control (push-button, motion, or flow-sensor activation)"
− - "BAS integration with scheduled operation and temperature feedback"
−default: "Aquastat + time clock combination (standard)"
−```
−
−## Recirculation Balancing
−
−Where the recirculation loop serves multiple branches or multiple risers, balancing valves or pressure-independent automatic balancing valves shall be provided at each branch take-off or riser base on the return circuit to ensure flow is proportional to the heat loss of each branch rather than taking the path of least resistance. Without balancing, the shortest-path branches circulate at excess flow while the longest branches stagnate, defeating Legionella control in the dead legs. Balancing valve locations and setpoints shall be coordinated with [[sync/domestic-water-piping]] and are [[drawing: as indicated on the plumbing riser diagrams]].
−
−```datasheet
−label: Recirculation Balancing Method
−type: select
−options:
− - "Manual balancing valve at each riser/branch with memory stop and flow indicator"
− - "Automatic pressure-independent thermostatic balancing valve at each branch"
− - "Not applicable — single-loop system with no branches"
−default: "Manual balancing valve at each riser/branch with memory stop and flow indicator"
−```
−
−# Controls and Monitoring
−
−Each water heater shall be provided with an operating thermostat (or modulating control as applicable to the equipment), a high-temperature limit cutout, a flame safeguard (gas) or thermal cutout (electric), a low-water cutoff where required by code or by ASME CSD-1, and the manufacturer's required combustion safety controls. The factory-supplied control package shall not be modified in the field; field-supplied controls shall be limited to those external to the appliance and shall not defeat any safety function of the factory controls.
−
−```datasheet
−label: BAS Integration
−type: select
−options:
− - "Monitor only — supply temperature, return temperature, pump status, alarm"
− - "Monitor and schedule — setpoints and operating schedule from BAS"
− - "Full BAS integration — read/write of setpoints, sequences, and diagnostics"
− - "No BAS integration — standalone controls"
−default: "Monitor only — supply temperature, return temperature, pump status, alarm"
−```
−
−Coordinate BAS points and communication protocol with [[sync/building-automation-system]]. Where the BAS provides monitoring of recirculation return temperature for Water Management Program compliance, the temperature sensor shall be installed in a thermowell at the heater inlet (return) and shall be calibrated at startup to within ±2°F of a traceable reference.
−
−```datasheet
−label: Recirculation Return Temperature Sensor
−type: radio
−options:
− - "Thermowell-mounted RTD with BAS input"
− - "Thermowell-mounted thermistor with BAS input"
− - "Surface-mount strap-on (not preferred — accuracy concerns)"
−default: "Thermowell-mounted RTD with BAS input"
−```
−
−# Installation
−
−## Equipment Setting
−
−Equipment shall be set level on a housekeeping pad or on the manufacturer's specified support. Tank-type heaters in seismic regions shall be anchored per the project's seismic anchorage details — typically two horizontal straps (upper and lower) anchored to adjacent structure or to a Unistrut/strut frame, with the heater isolated from rigid contact by manufacturer-furnished or field-cut spacers where required. Pre-approved seismic anchorage details (OSHPD, IAPMO, or AHJ-accepted) shall be used where available to avoid project-specific engineering for the anchorage.
−
−```datasheet
−label: Seismic Anchorage
−type: select
−options:
− - "Not required — SDC A or B"
− - "Two-strap horizontal anchorage to structure (SDC C and above, standard)"
− - "OSHPD / IAPMO pre-approved detail (high-seismic, healthcare)"
− - "Project-specific engineered anchorage"
−default: "Not required — SDC A or B"
−```
−
−## Piping Connections
−
−Cold-water inlet, hot-water outlet, and recirculation-return connections shall be made with unions or flanged connections (depending on size) between the heater and the building piping to permit heater service and replacement without cutting the building piping. Each connection shall include an isolation valve. Dielectric isolation shall be provided between the heater connections (typically copper or bronze) and any ferrous building piping per [[sync/domestic-water-piping]].
−
−Drain valves at the tank tapping shall be full-port ball valves with female hose-thread outlets, NSF 61/372 certified, with a threaded cap on the outlet. The Contractor shall verify that the drain valve location and the floor-drain layout permit complete drain-down of the tank without flooding.
−
−```datasheet
−label: Heater Piping Connection Method
−type: radio
−options:
− - "Unions on inlet and outlet (sizes through 2 in.)"
− - "Flanged connections on inlet and outlet (sizes 2-1/2 in. and larger)"
− - "Grooved mechanical couplings (where listed for application)"
−default: "Unions on inlet and outlet (sizes through 2 in.)"
−```
−
−## Gauges and Thermometers
−
−Each heater shall be provided with a pressure gauge on the inlet (cold) and a combination pressure-temperature gauge on the outlet (hot). The mixing valve outlet shall be provided with a temperature gauge or thermometer. The recirculation pump suction shall be provided with a temperature gauge or BAS sensor as established in Controls and Monitoring. Gauges and thermometers shall be installed in a position visible from the front of the heater without removing covers or shields.
−
−## Labeling and Valve Tagging
−
−Each heater, mixing valve, expansion tank, recirculation pump, and isolation valve shall be labeled with a permanent engraved or photo-laminated tag indicating the equipment identifier from the equipment schedule, the service (DHW supply, DHW recirculation, etc.), and any required setpoint. Valve tags shall be coordinated with the as-built piping schematic so a maintenance technician can identify and trace any tagged valve without ambiguity.
−
−```datasheet
−label: Valve and Equipment Tagging
−type: radio
−options:
− - "Engraved brass tags with chain or wire attachment (durable, preferred)"
− - "Photo-laminated plastic tags with chain or wire attachment"
−default: "Engraved brass tags with chain or wire attachment (durable, preferred)"
−```
−
−# Testing and Startup
−
−## Pre-Startup Inspection
−
−Before startup, the Contractor shall verify that the heater is correctly piped (inlet and outlet connections in the correct ports), that all isolation valves are open, that the tank is filled and vented of air, that the T&P relief valve is installed and the discharge piping is open and routed to a receptor, that the expansion tank pre-charge is correct, that the gas supply pressure (static) is within the heater's listed range, that the electrical disconnect is energized, that the venting is complete and unobstructed, and that the condensate drain (Category IV) is open and routed.
−
−## Startup
−
−Startup shall be performed by a factory-authorized technician for any heater with a manufacturer-required commissioning procedure, or by a qualified plumber/mechanic where the manufacturer accepts contractor startup. Startup procedure shall include: confirmation of fuel-gas dynamic supply pressure; manifold pressure setting; combustion testing (CO, CO₂, stack temperature) at high-fire and at low-fire/lowest stable rate; verification of high-temperature cutout operation by simulated overtemperature; verification of T&P relief valve operation by manual test lever; verification of recirculation pump rotation, flow, and aquastat function; setting of storage temperature and mixing-valve outlet temperature; and recording of all setpoints and as-found / as-left values in the startup report.
−
−## Field Performance Test
−
−Following startup, a field performance test shall be conducted to verify:
−
−- Outlet temperature at the heater within ±5°F of the storage setpoint after a recovery cycle from a fully drawn-down condition
−- Outlet temperature downstream of the master mixing valve within ±5°F of the distribution setpoint at the design flow rate and at a minimum draw representative of nighttime recirculation-only operation
−- Recirculation return temperature at the heater inlet equal to or greater than the distribution setpoint minus 10°F (typically ≥ 110°F when distribution is 120°F)
−- No discharge from the T&P relief valve during normal operation, including during recovery from full draw with the expansion tank in service
−- Combustion test results within the manufacturer's published range
−- For HPWH: measured heating capacity within 90 percent of the manufacturer's published capacity at the test conditions, and no condensate accumulation in the equipment cabinet
−
−```datasheet
−label: Field Performance Test — Required Documentation
−type: checkbox
−options:
− - "Outlet temperature at heater (storage setpoint verification)"
− - "Outlet temperature at mixing valve (distribution setpoint verification)"
− - "Recirculation return temperature at heater inlet"
− - "T&P relief valve manual test"
− - "Combustion test report (gas-fired)"
− - "HPWH heating capacity and condensate verification"
− - "Recirculation pump aquastat and control verification"
− - "Expansion tank pre-charge verification"
−default: "Outlet temperature at heater (storage setpoint verification)"
−```
−
−## Disinfection
−
−The water heater and storage tank shall be disinfected as part of the building's domestic-water system disinfection per [[sync/domestic-water-piping]] before being placed in service for potable use.
−
−# Delivery, Storage, and Handling
−
−Water-heating equipment shall be delivered to the site in the manufacturer's original packaging, with all factory protective covers, plugs, and tags in place. Equipment shall be inspected at delivery for shipping damage; damaged equipment shall be reported in writing to the carrier and to the manufacturer's authorized representative before installation and shall not be installed without disposition.
−
−Equipment shall be stored indoors, on level dunnage, protected from freezing, weather, construction water, and physical damage until installed. Storage tanks and packaged heaters with factory insulation shall not be stacked. Refrigerant-containing HPWHs shall be stored upright and shall not be tipped beyond the manufacturer's permitted shipping orientation; tipping a HPWH on its side can displace compressor oil and require an extended power-off settling period before startup.
−
−Vent components, gas piping, condensate piping, and small electrical components shall be stored in their original packaging, segregated from other trades' materials, and protected from foot traffic and construction dust.
−
−# Warranty
−
−The Contractor shall procure equipment carrying the standard manufacturer's warranty for the equipment category, and the warranty period shall commence at substantial completion or per the manufacturer's published policy. Standard commercial warranties typically include:
−
−- Tank (storage water heaters): 3 to 10 years (varies by manufacturer and model; commercial gas-fired storage typically 3 to 5 years on the tank)
−- Heat exchanger (gas-fired): 5 to 15 years (extended warranties common for condensing models)
−- Compressor (HPWH): 5 to 10 years
−- All other components: 1 year (parts; labor coverage varies)
−
−Where extended warranties or labor coverage are required by the contract documents, the requirement shall be stated explicitly in the equipment schedule and shall be documented in the closeout submittals. Warranty exclusions for water chemistry outside the manufacturer's stated acceptable range shall be acknowledged by the Owner in the project documents.
−
−```datasheet
−label: Warranty Requirement
−type: select
−options:
− - "Manufacturer standard warranty"
− - "Manufacturer standard + extended parts (5 years minimum)"
− - "Manufacturer standard + extended parts and labor (5 years minimum)"
− - "Project-specified warranty per equipment schedule"
−default: "Manufacturer standard warranty"
−```
−
−# Spare Parts
−
−The Contractor shall deliver to the Owner at substantial completion the following spare parts, marked with the equipment identifier and stored in a labeled container in the mechanical room or in a location designated by the Owner:
−
−- One complete set of replacement gaskets for each unique heater connection and each unique mixing valve
−- One spare sacrificial anode rod for each glass-lined tank
−- One spare T&P relief valve per unique set pressure / set temperature combination
−- One spare recirculation pump cartridge or pump head (for cartridge-style wet-rotor pumps) per unique pump model
−- One spare expansion tank diaphragm assembly per unique expansion tank model (where field-replaceable)
−- One spare aquastat or temperature controller per unique model
−- For Category IV equipment, one spare condensate-neutralizer media charge
−
−```datasheet
−label: Spare Parts Delivery
−type: checkbox
−options:
− - "Replacement gaskets for heater and mixing valve connections"
− - "Spare sacrificial anode rod (one per glass-lined tank)"
− - "Spare T&P relief valve (one per unique set pressure)"
− - "Spare recirculation pump cartridge or pump head"
− - "Spare expansion tank diaphragm assembly (field-replaceable models)"
− - "Spare aquastat or temperature controller"
− - "Spare condensate-neutralizer media (Category IV)"
−default: "Replacement gaskets for heater and mixing valve connections"
−```
+---
+title: Commercial Water Heaters
+category: Plumbing
+toc_depth: 3
+description: >
+ When to use: Commercial domestic-hot-water (DHW) generation equipment serving commercial, institutional, and industrial buildings. Covers storage gas-fired water heaters (atmospheric, power-vented, power-direct-vented, and condensing), commercial electric storage water heaters, instantaneous and tankless gas water heaters (including condensing), heat-pump water heaters (HPWH), indirect-fired storage tanks heated by a boiler heat exchanger or by solar / waste-heat sources, and semi-instantaneous packaged units. Includes storage tanks (glass-lined, stainless, cement-lined), thermal expansion tanks, ASSE 1017 master mixing valves and ASSE 1070 point-of-use temperature-limiting devices, recirculation pumps and the circulating system, ASHRAE 188 Legionella requirements (storage and distribution setpoints, mixing-valve setpoints), and the venting, fuel-gas connection, condensate drain, electrical, and seismic provisions associated with the water-heating equipment itself.
+
+ Not intended for: Domestic water piping upstream and downstream of the equipment (see [[sync/domestic-water-piping]]); the plumbing fixtures served (see [[sync/plumbing-fixtures]]); sanitary-waste and vent piping for tank, T&P relief, and condensate routing to drain (see [[sync/sanitary-waste-and-vent-piping]]); building water-service backflow prevention assemblies (see [[sync/backflow-prevention]]); solar thermal collectors and solar array piping (separate scope; indirect-fired storage tanks heated by a solar loop are within this scope but the collector array is not); hydronic-heating boilers serving space-heating loops (those serve the building-heating system, not DHW — see [[sync/hydronic-piping]] for the boiler-side hydronic piping, with indirect DHW tank coil connections covered here); pool and spa water heating; process and industrial hot water generation above standard DHW temperatures; steam-to-water DHW heat exchangers in central steam plants (a related but distinct equipment category).
+---
+
+# Scope {toc}
+
+## This standard covers the equipment, accessories, controls, vent and combustion-air system, fuel-gas piping connection, electrical connection, condensate handling, seismic restraint, installation, startup, and testing of commercial domestic-hot-water generating equipment. {note}
+## The scope of this standard begins at the cold-water inlet connection to the water heater or storage tank and terminates at the hot-water and recirculation-return outlet connections downstream of the master mixing valve. {note}
+## The domestic-water piping that conveys water to and from this equipment is the subject of [[sync/domestic-water-piping]]. {note}
+
+## Equipment selection, capacity, redundancy, location, and the recirculation-system layout are [[drawing: as indicated on the plumbing equipment schedules, mechanical room plans, and water heater piping diagrams]]. {note}
+## This standard establishes the materials, performance, controls, and installation requirements that govern those drawings. {note}
+
+## All wetted components in contact with potable water shall comply with NSF/ANSI 61 for health effects and NSF/ANSI/CAN 372 for lead-free content (0.25 percent maximum weighted average lead content of wetted surface area), a federal requirement under the Safe Drinking Water Act applicable to all plumbing components installed on or after January 4, 2014.
+
+## This standard establishes the equipment-level temperature, mixing-valve, and recirculation requirements necessary to support the project's Water Management Program.
+
+## Building-wide Legionella management is the subject of a project-specific Water Management Program developed in accordance with ASHRAE 188 by the Owner's design team and operations staff; this standard does not constitute the program itself. {note}
+
+# Referenced Standards {toc}
+
+## Equipment, components, and installation shall comply with the latest adopted edition of the following standards and codes.
+
+| Standard | Title |
+|----------|-------|
+| ASHRAE 188 | Legionellosis: Risk Management for Building Water Systems |
+| ASHRAE 90.1 | Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings (water heater efficiency, pipe insulation, recirculation controls) |
+| ASHRAE 90.2 | Energy-Efficient Design of Low-Rise Residential Buildings (referenced where residential-style equipment is installed in commercial small projects) |
+| ASHRAE 62.1 | Ventilation and Acceptable Indoor Air Quality (combustion-air and mechanical-room ventilation) |
+| IECC | International Energy Conservation Code (commercial provisions referencing ASHRAE 90.1) |
+| 10 CFR Part 431 | DOE Energy Conservation Standards for Commercial Water Heaters (thermal efficiency, standby loss) |
+| 10 CFR Part 430 | DOE Energy Conservation Standards for Consumer Water Heaters (UEF — applies to residential-grade units) |
+| ANSI Z21.10.1 / CSA 4.1 | Gas Water Heaters — Volume I, Storage Water Heaters with Input Ratings of 75,000 Btu/h and Under |
+| ANSI Z21.10.3 / CSA 4.3 | Gas-Fired Water Heaters for Storage and Instantaneous Water Heaters (commercial; inputs above 75,000 Btu/h, and circulating and instantaneous types) |
+| UL 174 | Household Electric Storage Tank Water Heaters |
+| UL 1453 | Electric Booster and Commercial Storage Tank Water Heaters |
+| UL 1995 / CSA C22.2 No. 236 | Heating and Cooling Equipment (referenced for HPWH packaged units, superseded for new HPWHs by UL 60335-2-40) |
+| UL 60335-2-40 / CSA C22.2 No. 60335-2-40 | Household and Similar Electrical Appliances — Safety — Particular Requirements for Electrical Heat Pumps, Air-Conditioners and Dehumidifiers |
+| ASME Boiler and Pressure Vessel Code, Section VIII Division 1 | Rules for Construction of Pressure Vessels (tanks exceeding the commercial threshold) |
+| ASME CSD-1 | Controls and Safety Devices for Automatically Fired Boilers (where applicable to high-input water heaters) |
+| NSF/ANSI 5 | Water Heaters, Hot Water Supply Boilers, and Heat Recovery Equipment (commercial food service and hygiene-sensitive applications) |
+| NSF/ANSI 61 | Drinking Water System Components — Health Effects |
+| NSF/ANSI/CAN 372 | Drinking Water System Components — Lead Content |
+| ASSE 1003 | Performance Requirements for Water Pressure Reducing Valves (referenced for upstream PRV coordination) |
+| ASSE 1017 | Performance Requirements for Temperature Actuated Mixing Valves for Hot Water Distribution Systems (master mixing valve) |
+| ASSE 1070 / ASME A112.1070 / CSA B125.70 | Performance Requirements for Water Temperature Limiting Devices (point-of-use thermostatic) |
+| ASSE 1082 | Performance Requirements for Water Heaters with Integral Temperature Limiting Capability |
+| ANSI Z21.22 / CSA 4.4 | Relief Valves for Hot Water Supply Systems (T&P relief valves) |
+| NFPA 54 / ANSI Z223.1 | National Fuel Gas Code |
+| IFGC | International Fuel Gas Code |
+| NFPA 70 | National Electrical Code |
+| NFPA 31 | Standard for the Installation of Oil-Burning Equipment (where oil-fired) |
+| UL 1738 | Venting Systems for Gas-Burning Appliances, Categories II, III, and IV |
+| UL 103 | Factory-Built Chimneys for Residential Type and Building Heating Appliances (Type B and L vent) |
+| UL 174 | Household Electric Storage Tank Water Heaters |
+| AGA / CSA NGV-1 | Compressed Natural Gas Vehicle Fueling Connection Devices (referenced for fuel-gas connection components where applicable) |
+| ASME A112.4.1 | Water Heater Relief Valve Drain Tubes |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures (seismic restraint) |
+| OSHPD / IAPMO listings | Pre-approved seismic anchorage details for water heaters in high-seismic jurisdictions |
+| IPC | International Plumbing Code |
+| UPC | Uniform Plumbing Code |
+
+## Where the contract documents, the Authority Having Jurisdiction (AHJ), or a referenced standard impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## The applicable plumbing code (IPC or UPC as adopted by the jurisdiction), the applicable mechanical code, and the applicable fuel-gas code (NFPA 54 / IFGC) shall take precedence over all other references on any matter directly addressed by those codes.
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### Contractor shall submit the following for the Engineer's review prior to procurement and installation.
+### Work shall not proceed on any water-heating equipment until the corresponding submittals have been reviewed and returned.
+
+- Product data for each water heater, indicating the manufacturer's model number, fuel type, input rating (Btu/h or kW), storage volume, recovery rate at the specified temperature rise, first-hour rating where applicable, thermal efficiency or UEF, vent category (I, II, III, or IV), permitted vent materials and maximum vent length, electrical characteristics, gas-train pressure range, applicable certification listings (ANSI Z21.10.3, UL 1453, UL 60335-2-40, or other as appropriate), and NSF/ANSI 5 listing where required by the application
+- Product data for storage tanks (indirect-fired, ASME, or supplemental), including tank material and lining (glass-lined, stainless steel Type 316L, cement-lined), insulation R-value, working pressure, T&P relief connection size, anode rod type and replacement access, and applicable certification (ASME Section VIII Div 1 stamp where required, NSF/ANSI 61)
+- Product data for the master mixing valve (ASSE 1017), including body material, paired hot/cold/blend connection sizes, minimum and maximum flow rate at the specified pressure drop, setpoint adjustment range, accuracy, integral isolation and check valves, and union or flanged service connections
+- Product data for any point-of-use temperature-limiting devices (ASSE 1070) coordinated with [[sync/plumbing-fixtures]]
+- Product data for the thermal expansion tank, including pre-charge pressure, acceptance volume, total volume, diaphragm or bladder material (potable PE-X lined or butyl), and NSF/ANSI 61 certification for wetted parts
+- Product data for the hot-water recirculation pump, including flow rate, head, motor data, wetted materials (bronze or stainless steel), NSF/ANSI 61 certification, and control type (time clock, aquastat, demand, or combination)
+- Product data for the T&P relief valve per ANSI Z21.22, including set pressure, set temperature, discharge capacity (Btu/h), and connection size; provide separate documentation for tank T&P relief and any heat-exchanger or system relief valves
+- Combustion-air and venting plan for each gas-fired heater, including vent category, vent material and diameter, total equivalent vent length, termination location and clearances, common venting calculations where multiple heaters share a vent, and condensate drain routing for Category IV (condensing) equipment
+- Fuel-gas connection details, including supply pressure at the heater, gas-train components (manual shutoff, sediment trap / dirt leg, union, regulator if required), pipe sizing verification, and CSST or rigid-pipe details
+- Electrical connection details, including circuit ampacity, overcurrent protection size, disconnect location and rating, equipment grounding and bonding (coordinate with [[sync/grounding-and-bonding]] for electric units), and integration with the building energy-management system or BAS (coordinate with [[sync/building-automation-system]])
+- Heat-pump water heater submittals shall additionally include heating capacity at design ambient conditions, COP at AHRI rating conditions, sound level (sones or dBA at specified distance), refrigerant type and charge, condensate generation rate, and any space cooling or dehumidification effect on the mechanical room
+- Seismic anchorage calculations or pre-approved seismic anchorage details (OSHPD, IAPMO, or equivalent) where required by the project's Seismic Design Category
+- Startup and commissioning checklist and the manufacturer's installation and operation manuals
+- Schematic piping diagram showing the heater(s), storage tanks, mixing valves, expansion tank, recirculation pump and balancing valves, isolation valves, gauges, thermometers, drain valves, and union connections, with valve tags assigned and a flow path traceable through the diagram
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Water heater product data with input, recovery, efficiency, vent category"
+ - "Storage tank product data with lining, insulation, ASME stamp where required"
+ - "Master mixing valve product data (ASSE 1017)"
+ - "Point-of-use temperature-limiting device product data (ASSE 1070)"
+ - "Thermal expansion tank product data (NSF 61 wetted parts)"
+ - "Recirculation pump product data (NSF 61 wetted parts)"
+ - "T&P relief valve product data (ANSI Z21.22)"
+ - "Combustion-air and venting plan"
+ - "Fuel-gas connection details"
+ - "Electrical connection details"
+ - "HPWH-specific submittals (heating capacity, COP, sound, refrigerant)"
+ - "Seismic anchorage calculations or pre-approved details"
+ - "Startup / commissioning checklist and O&M manuals"
+ - "Schematic piping diagram with valve tagging"
+default: "Water heater product data with input, recovery, efficiency, vent category"
+```
+
+### The Contractor shall submit the action submittals listed above for the Engineer's review prior to procurement and installation.
+
+### Work shall not proceed on any water-heating equipment until the corresponding submittals have been reviewed and returned.
+
+## Closeout Submittals {toc}
+
+### Contractor shall provide the following at substantial completion before the water-heating system is accepted.
+
+- As-built piping schematic showing actual installed configuration, valve tag locations, gauge and thermometer locations, drain valve locations, and the final routing of vent, gas, electrical, and condensate connections
+- Operation and maintenance (O&M) manuals for the water heater, storage tank, mixing valve, expansion tank, recirculation pump, T&P relief valve, controls, and any auxiliary equipment, with the manufacturer's recommended maintenance intervals tabulated
+- Manufacturer's startup report signed by the manufacturer's authorized service representative or by a technician trained and certified by the manufacturer, indicating that combustion, water-side, and electrical systems were verified per the manufacturer's commissioning procedure
+- Combustion test reports for each gas-fired heater, recording fuel-gas supply pressure (static and dynamic), manifold pressure, CO and CO₂ in the flue gas, stack temperature, and combustion efficiency at high-fire and (where modulating or staged) at the lowest stable fire rate
+- Field test reports for water-side performance — measured recovery rate, measured outlet temperature at the heater, measured outlet temperature downstream of the master mixing valve, measured recirculation return temperature at the heater inlet, and verification that the T&P relief valve and any energy cut-out controls function as specified
+- Water Management Program documentation interface — recorded equipment setpoints, recirculation control schedule, and any operational logs required by the Owner's ASHRAE 188 program
+- Warranty documentation for the water heater, the storage tank, the heat exchanger or anode rod (where covered separately), and all auxiliary equipment
+
+```datasheet
+label: Closeout Submittals Required
+type: checkbox
+options:
+ - "As-built piping schematic with valve tag, gauge, thermometer, and drain locations"
+ - "Operation and maintenance (O&M) manuals with maintenance intervals tabulated"
+ - "Manufacturer's signed startup report"
+ - "Combustion test reports for each gas-fired heater"
+ - "Field test reports for water-side performance"
+ - "Water Management Program documentation interface (setpoints, schedule, logs)"
+ - "Warranty documentation for heater, tank, heat exchanger/anode, and auxiliaries"
+default: "As-built piping schematic with valve tag, gauge, thermometer, and drain locations"
+```
+
+### The Contractor shall provide the closeout submittals listed above at substantial completion before the water-heating system is accepted.
+
+# Quality Assurance {toc}
+
+## Installer Qualifications {toc}
+
+### Water-heating equipment installation shall be performed by personnel licensed in the trade or trades that apply to the equipment installed — plumbing license for water-side piping, mechanical license for venting, fuel-gas license where required by the AHJ for fuel-gas connection, and electrical license for the electrical connection.
+
+### Where the manufacturer requires a factory-authorized startup, startup and initial commissioning shall be performed by a technician currently certified by the equipment manufacturer.
+
+### The Contractor shall furnish documentation of current manufacturer certification before startup begins.
+
+### Refrigerant-containing heat-pump water heaters with refrigerant quantities at or above the EPA Section 608 threshold (currently 5 lb for most HFC charges) shall be installed and serviced only by EPA 608-certified technicians.
+
+### The Contractor shall maintain EPA 608 certification documentation on site.
+
+## Product Listing and Certification {toc}
+
+### Each water heater shall bear the certification mark of a Nationally Recognized Testing Laboratory (NRTL) recognized by OSHA for the applicable product standard — typically ANSI Z21.10.3 / CSA 4.3 for commercial gas, UL 174 or UL 1453 for electric, and UL 60335-2-40 for HPWH.
+
+### Storage tanks for which ASME Section VIII Division 1 construction is required shall bear the ASME "U" or "UM" stamp.
+
+### Where the application requires NSF/ANSI 5 listing (commercial food service, healthcare hot-water washing systems, and similar hygiene-sensitive applications), the equipment shall bear the NSF/ANSI 5 listing mark.
+
+## ASME Pressure Vessel Thresholds {toc}
+
+### A water-heating vessel is considered a "pressure vessel" subject to ASME Boiler and Pressure Vessel Code Section VIII Division 1 construction and stamping requirements when any one of the threshold criteria below is exceeded. {note}
+
+### Equipment is subject to ASME Section VIII Division 1 construction and stamping when storage volume exceeds 120 gal, input rating exceeds 200,000 Btu/h, working pressure exceeds 160 psi, or operating temperature exceeds 210°F.
+
+### Equipment selected at or above any ASME threshold shall be ASME-stamped, and the certification documentation shall be included in the closeout submittals.
+
+### The Engineer shall not specify equipment that exceeds an ASME threshold by a small margin in order to avoid the requirement; ASME construction is appropriate at and above these thresholds and shall be procured accordingly.
+
+## Lead-Free Compliance {toc}
+
+### All wetted components — heater inlet/outlet fittings, dip tubes, tappings, drain valves, T&P relief valve wetted parts, anode rod connections, mixing valve, expansion tank diaphragm or bladder, recirculation pump wetted parts, gauges, and unions — shall be certified to NSF/ANSI/CAN 372, confirming that the weighted average lead content of the wetted surface area does not exceed 0.25 percent.
+
+### This NSF/ANSI/CAN 372 lead-content requirement is a federal requirement under the Reduction of Lead in Drinking Water Act and is not subject to project-level waiver.
+
+## Manufacturer Authorization {toc}
+
+### Equipment shall be procured through a manufacturer-authorized distributor or representative.
+
+### The Owner shall not be required to engage a non-authorized rebuilder, refurbisher, or third party for warranty service during the warranty period.
+
+### The Contractor shall furnish the local authorized service representative's contact information in the O&M manuals.
+
+# Environmental and Service Conditions {toc}
+
+## Installation Environment {toc}
+
+### Water heaters shall be located in a conditioned mechanical space sized to provide combustion air, ventilation, equipment service clearance, and seismic anchorage as required by the equipment listing and by NFPA 54 / IFGC for fuel-fired equipment.
+
+```datasheet
+label: Mechanical Room Floor Drain
+type: radio
+options:
+ - "Yes — floor drain provided in mechanical room"
+ - "No — indirect waste receptor or condensate sump provided"
+default: "Yes — floor drain provided in mechanical room"
+```
+
+### The mechanical space shall not be subject to freezing temperatures during normal building operation; freeze protection shall be provided where freezing is possible, particularly for condensing equipment with condensate piping.
+
+### The mechanical space shall have a floor drain capable of accepting the maximum flow of the T&P relief valve discharge, condensate discharge, and tank drain-down without flooding adjacent areas.
+
+### Where a floor drain is not available, an indirect-waste receptor or an alarmed and pumped condensate-collection sump shall be provided.
+
+### The mechanical space serving a heat-pump water heater shall be sized and ventilated to allow the HPWH to operate without driving space temperature below the manufacturer's minimum operating ambient temperature.
+
+### Where the heat-pump cooling effect would over-cool the mechanical space during the cooling season, ductwork shall be installed to draw air from a thermally suitable source and return it to a location that does not adversely affect adjacent occupied spaces.
+
+## Combustion Air {toc}
+
+### Fuel-fired water heaters require combustion air at a rate determined by the input rating of the heater and the venting category. {note}
+
+```datasheet
+label: Combustion Air Source
+type: select
+options:
+ - "Direct-vent (sealed combustion) — concentric or parallel pipe from outside"
+ - "Power-vent with indoor combustion air per NFPA 54 openings"
+ - "Atmospheric / natural-draft with indoor combustion air per NFPA 54 openings"
+ - "Engineered combustion-air duct with interlocked supply fan"
+ - "Not applicable — electric or heat-pump (no combustion)"
+default: "Direct-vent (sealed combustion) — concentric or parallel pipe from outside"
+```
+
+### For Category I and II atmospheric and natural-draft heaters, combustion air shall be supplied per NFPA 54 / IFGC by openings communicating with the outside, by an engineered combustion-air duct, or by an interlocked mechanical combustion-air system.
+
+### For Category III and IV power-vented and direct-vented heaters, combustion air shall be drawn through a sealed combustion-air pipe terminated outside the building in accordance with the manufacturer's vent termination requirements.
+
+## Service Clearances {toc}
+
+### Service clearances shall meet or exceed the manufacturer's published minimums and the working clearances required by NFPA 70 for the electrical disconnect.
+
+### Tank-type heaters shall provide overhead access for anode rod replacement equal to the rod length plus a working margin (typically 36 in. above the tank for full-length rods, or as published by the manufacturer for flexible / segmented rods).
+
+### Direct-vent terminations shall meet the manufacturer's clearance to building openings, soffits, grade, snow line, and adjacent terminations.
+
+## Water Quality {toc}
+
+### Domestic-water inlet water quality affects the service life of all wetted components, particularly anode rods, glass-lined tank linings, and brazed-plate heat exchangers in indirect-fired equipment. {note}
+
+```datasheet
+label: Inlet Water Treatment
+type: select
+options:
+ - "None — municipal supply within manufacturer's acceptable range"
+ - "Water softener upstream of cold-water inlet"
+ - "Scale-control system (template-assisted crystallization or equivalent)"
+ - "Engineered treatment per project water analysis"
+default: "None — municipal supply within manufacturer's acceptable range"
+```
+
+### Where the inlet water hardness exceeds 7 grains per gallon (gpg), softening or scale-control treatment shall be evaluated by the Engineer.
+
+### Where the chloride level exceeds 100 mg/L or the water is supplied by an on-site well of unknown chemistry, the tank lining material shall be selected for the water chemistry (stainless steel 316L for high chlorides; glass-lined for typical municipal supply; cement-lined for very large indirect tanks).
+
+### The Contractor shall not be responsible for premature equipment failure caused by water chemistry outside the manufacturer's published acceptable range, provided the equipment was installed and started up correctly.
+
+# Water Heater Selection {toc}
+
+## General Selection Criteria {toc}
+
+### Water heater type shall be selected to suit the building's hot-water load profile (peak, recovery, and standby), the available utility services (gas service pressure and electric service capacity), the climate (which affects HPWH performance and condensate management), the available mechanical room space, the noise sensitivity of adjacent spaces, the redundancy requirement, and the project's energy and emissions goals.
+
+```datasheet
+label: Water Heater Type
+type: radio
+options:
+ - "Gas-fired storage — atmospheric (Category I)"
+ - "Gas-fired storage — power-vented (Category III)"
+ - "Gas-fired storage — power direct-vented (Category III, sealed combustion)"
+ - "Gas-fired storage — condensing (Category IV)"
+ - "Electric storage — commercial (UL 1453)"
+ - "Gas-fired instantaneous / tankless — condensing"
+ - "Gas-fired instantaneous / tankless — non-condensing"
+ - "Heat-pump water heater (HPWH)"
+ - "Indirect-fired storage tank — heated by external boiler"
+ - "Indirect-fired storage tank — heated by solar / waste-heat source"
+ - "Semi-instantaneous packaged water heater"
+default: "Gas-fired storage — condensing (Category IV)"
+```
+
+### The Engineer shall size the equipment based on the calculated hot-water demand using ASHRAE Handbook procedures or an equivalent recognized method; this standard establishes the equipment performance requirements that govern after the selection is made.
+
+### Storage gas-fired heaters are the established standard for commercial DHW in buildings with significant peak-to-average load ratios, and instantaneous (tankless) gas heaters minimize standby loss and footprint and are well suited to applications with steady moderate load or to point-of-use service. {note}
+
+### Heat-pump water heaters offer high efficiency (COP typically 2 to 4) and electrification but require careful mechanical-room sizing and condensate management. {note}
+
+### Indirect-fired storage tanks are appropriate where a boiler plant already exists for space heating, deferring the boiler's summer shutdown and providing a domestic-water load, and semi-instantaneous packaged units integrate a small buffer tank with a tankless heat exchanger to provide stable outlet temperature with limited standby loss. {note}
+
+## Input Rating {toc}
+
+### Input rating shall be sized by the Engineer to satisfy the peak hot-water demand in combination with the storage volume.
+### The input rating governs the recovery capacity and the standby losses of the equipment. {note}
+
+```datasheet
+label: Heater Input Rating — Gas
+type: range
+unit: Btu/h
+drawing_ref: true
+options:
+ min: 75000
+ max: 4000000
+ setpoints: [75000, 100000, 199000, 300000, 500000, 750000, 1000000, 1500000, 2000000, 3000000, 4000000]
+default: 500000
+```
+
+```datasheet
+label: Heater Input Rating — Electric
+type: range
+unit: kW
+drawing_ref: true
+options:
+ min: 6
+ max: 180
+ setpoints: [6, 9, 12, 18, 24, 36, 54, 72, 90, 120, 150, 180]
+default: 36
+```
+
+### The input rating shall be [[drawing: as indicated on the water heater schedule]]; the datasheet establishes the typical input rating ranges, and the Engineer's calculation governs the actual selected value.
+
+## Recovery Capacity {toc}
+
+### Recovery capacity shall be expressed at a standard temperature rise (ΔT) and shall be sufficient, in combination with the storage volume, to satisfy the peak draw without exceeding the allowable temperature drop at the most remote fixture.
+
+```datasheet
+label: Recovery at 100°F ΔT
+type: range
+unit: GPH
+drawing_ref: true
+options:
+ min: 30
+ max: 5000
+ setpoints: [30, 50, 100, 200, 350, 500, 750, 1000, 1500, 2000, 3000, 5000]
+default: 500
+```
+
+### Recovery at 100°F rise is the standard reference condition for commercial gas-fired equipment in the U.S. market; recovery at the project-specific design ΔT shall be confirmed against the equipment manufacturer's published performance curves.
+
+## Storage Volume {toc}
+
+### Storage volume shall be sized to absorb the difference between peak demand and recovery capacity, with a margin sufficient to maintain delivery temperature at the most remote fixture during the design draw.
+
+```datasheet
+label: Storage Volume
+type: range
+unit: gal
+drawing_ref: true
+options:
+ min: 0
+ max: 5000
+ setpoints: [0, 6, 19, 40, 50, 75, 80, 100, 119, 120, 175, 250, 350, 500, 750, 1000, 1500, 2500, 5000]
+default: 119
+```
+
+### Increasing the storage volume reduces the required input rating; the Engineer shall optimize the storage-to-input ratio based on the load profile, the energy cost, the available space, and ASME-threshold considerations.
+
+### Tank-type heaters and supplemental storage tanks at 119 gal nominal and below are commonly selected to remain below the 120-gal ASME threshold; this is a legitimate design choice but shall not be used as a reason to under-size storage where the load profile genuinely calls for a larger tank.
+
+### Tanks at 120 gal nominal and above shall be ASME-stamped per the threshold criteria in this standard.
+
+## Efficiency {toc}
+
+### All water heaters shall meet or exceed the applicable minimum efficiency requirement under ASHRAE 90.1, the IECC, and the DOE Energy Conservation Standards (10 CFR Part 431 for commercial; 10 CFR Part 430 for residential-grade units installed in commercial small projects).
+
+```datasheet
+label: Minimum Efficiency Basis
+type: select
+options:
+ - "Uniform Energy Factor (UEF) per DOE 10 CFR Part 430 (residential-grade)"
+ - "Thermal Efficiency (Et) and Standby Loss (SL) per DOE 10 CFR Part 431 (commercial)"
+ - "Coefficient of Performance (COP) at AHRI rating conditions (HPWH)"
+default: "Thermal Efficiency (Et) and Standby Loss (SL) per DOE 10 CFR Part 431 (commercial)"
+```
+
+```datasheet
+label: Minimum Thermal Efficiency — Gas-Fired (Et)
+type: range
+unit: "%"
+options:
+ min: 80
+ max: 99
+ setpoints: [80, 82, 90, 92, 94, 95, 96, 97, 98, 99]
+default: 94
+```
+
+```datasheet
+label: Minimum UEF — Residential-Grade (where applicable)
+type: range
+unit: ""
+options:
+ min: 0.60
+ max: 4.00
+ step: 0.01
+default: 0.81
+```
+
+```datasheet
+label: Minimum HPWH COP at AHRI Conditions (where applicable)
+type: range
+unit: ""
+options:
+ min: 2.0
+ max: 5.0
+ step: 0.1
+default: 3.0
+```
+
+### Performance shall be reported as Uniform Energy Factor (UEF) for residential-grade equipment within DOE scope and as Thermal Efficiency (Et) and Standby Loss (SL) for commercial equipment within DOE scope.
+
+### The Engineer shall verify that the specified equipment satisfies the federal floor and any state or local energy-code-amended requirement.
+
+# Storage Tanks {toc}
+
+## Tank Construction and Lining {toc}
+
+### Storage tanks shall be selected with a lining material suitable for the inlet water chemistry, the operating temperature, and the service life expected for the application.
+
+```datasheet
+label: Storage Tank Lining
+type: select
+options:
+ - "Glass-lined steel with sacrificial anode rod (standard)"
+ - "Stainless steel Type 316L (no anode required)"
+ - "Cement-lined steel (very large indirect tanks, raw water service)"
+ - "Integral to packaged heater — manufacturer's standard lining"
+default: "Glass-lined steel with sacrificial anode rod (standard)"
+```
+
+### Glass-lined steel is the established standard for typical municipal water at storage temperatures up to 180°F; the porcelain-enamel lining is dependent on a functioning sacrificial anode rod for cathodic protection of the steel substrate at any small lining imperfection. {note}
+
+### Stainless steel Type 316L tanks eliminate the anode rod and tolerate higher chloride water chemistries, and are appropriate for water with chlorides above 100 mg/L, for installations where anode-rod maintenance is not feasible, and for hygiene-sensitive applications. {note}
+
+### Cement-lined tanks are used for very large indirect tanks and for raw or untreated water service, and rely on the cement lining's high pH to passivate the steel. {note}
+
+### Cement-lined tanks shall not be drained and left empty for extended periods, which causes the lining to dry and crack.
+
+## Anode Rod {toc}
+
+```datasheet
+label: Anode Rod Type
+type: select
+options:
+ - "Magnesium — sacrificial (standard for municipal water)"
+ - "Aluminum-zinc — sacrificial (where magnesium produces odor)"
+ - "Powered impressed-current — non-sacrificial"
+ - "Not applicable — stainless steel or cement-lined tank"
+default: "Magnesium — sacrificial (standard for municipal water)"
+```
+
+### Glass-lined tanks shall be provided with at least one sacrificial anode rod, accessible from the top of the tank, of magnesium, aluminum-zinc, or powered-impressed-current type.
+
+### Magnesium anodes are the standard for typical municipal water and provide strong cathodic protection at the cost of faster consumption and occasional sulfate-reducing-bacteria odor in low-flow installations; aluminum-zinc anodes are appropriate where magnesium produces "rotten egg" odor or where water hardness is low, and powered-impressed-current anode systems eliminate sacrificial-anode replacement at the cost of a powered control unit and are appropriate for inaccessible installations. {note}
+
+### Anode rods shall be accessible for inspection and replacement without disturbing the surrounding piping.
+
+### The Contractor shall confirm the overhead clearance required for the rod length and shall locate the tank accordingly.
+
+### Where overhead clearance is restricted, flexible or segmented anode rods rated by the manufacturer for the application shall be specified.
+
+## Tank Insulation {toc}
+
+```datasheet
+label: Tank Insulation
+type: select
+options:
+ - "Factory insulated, R-value meeting ASHRAE 90.1 / DOE minimum"
+ - "Factory insulated, R-value exceeding ASHRAE 90.1 by 25 percent or more"
+ - "Field-applied supplemental insulation in addition to factory insulation"
+default: "Factory insulated, R-value meeting ASHRAE 90.1 / DOE minimum"
+```
+
+### Tanks shall be factory-insulated with rigid foam, fiberglass, or equivalent to satisfy the standby-loss requirement under DOE 10 CFR Part 431 and ASHRAE 90.1.
+
+### Field-applied insulation on the tank exterior is not a substitute for factory insulation.
+
+### Where the tank is located in an unconditioned space and the factory insulation is at the federal minimum, supplemental field-applied insulation per the Engineer's direction may be provided.
+
+## Indirect-Fired Tank Coil {toc}
+
+```datasheet
+label: Indirect Tank Coil Wall
+type: radio
+options:
+ - "Single-wall coil — boiler loop contains water only (no glycol or chemicals)"
+ - "Double-wall coil — boiler loop contains glycol or chemical treatment"
+ - "Not applicable — not indirect-fired"
+default: "Not applicable — not indirect-fired"
+```
+
+### Indirect-fired storage tanks shall include an internal heat-exchanger coil sized for the design heating load at the boiler-supply temperature provided by the [[sync/hydronic-piping]] boiler loop.
+
+### The coil material shall be stainless steel or copper, sized for the boiler-side flow rate, and provided with a separate isolation valve and union on both supply and return connections to permit coil replacement.
+
+### The boiler loop and the domestic water in the tank shall be physically separated by the coil wall.
+
+### Double-wall construction shall be provided where the boiler loop contains glycol or chemical treatment, where required by code, or where the AHJ requires separation between potable water and a chemically treated fluid.
+
+# Venting and Combustion {toc}
+
+## Vent Category {toc}
+
+### Gas-fired water heaters are classified by venting category under ANSI Z21.10.3 and NFPA 54 by combustion-system pressure (positive or negative within the vent) and by the dew point of the flue gas (above or below). {note}
+
+```datasheet
+label: Vent Category
+type: select
+options:
+ - "Category I — non-positive, non-condensing (atmospheric, Type B vent)"
+ - "Category II — non-positive, condensing (uncommon)"
+ - "Category III — positive, non-condensing (power-vented)"
+ - "Category IV — positive, condensing"
+ - "Not applicable — electric, HPWH, or indirect-fired"
+default: "Category IV — positive, condensing"
+```
+
+### Category I is non-positive vent pressure, non-condensing — typical atmospheric heaters using Type B vent; Category II is non-positive vent pressure, condensing — uncommon; Category III is positive vent pressure, non-condensing — power-vented non-condensing heaters using special vent material rated for positive pressure; Category IV is positive vent pressure, condensing — condensing heaters using AL29-4C stainless steel, polypropylene, or PVC/CPVC vent piping as listed by the manufacturer. {note}
+
+## Vent Material {toc}
+
+### Vent material shall be selected to match the equipment's vent category, to be listed by the equipment manufacturer for the specific model, and to comply with UL 1738 (Categories II, III, IV) or UL 103 (Type B and L vent for Category I).
+
+```datasheet
+label: Vent Material
+type: select
+options:
+ - "Type B double-wall metal (Category I only)"
+ - "AL29-4C stainless steel (Category III and IV)"
+ - "Polypropylene — UL 1738 listed (Category III and IV)"
+ - "PVC — manufacturer-listed and AHJ-accepted (Category IV only)"
+ - "CPVC — manufacturer-listed and AHJ-accepted (Category IV only)"
+ - "Not applicable — electric, HPWH, or indirect-fired"
+default: "AL29-4C stainless steel (Category III and IV)"
+```
+
+### PVC and CPVC vent material is permitted only where specifically listed by the equipment manufacturer and where allowed by the applicable code and AHJ.
+
+### AL29-4C stainless steel and listed polypropylene are the durable choices for Category IV vent and shall be specified where life-cycle, code, or AHJ considerations warrant.
+
+### Some jurisdictions and many model codes are moving away from PVC vent for gas-fired condensing appliances due to long-term durability and flue-gas temperature concerns. {note}
+
+## Vent Sizing and Termination {toc}
+
+### Vent diameter, total equivalent length, number and type of fittings, and termination clearances shall comply with the equipment manufacturer's installation instructions and with NFPA 54 / IFGC.
+
+### Termination location and configuration are [[drawing: as indicated on the venting plan and mechanical roof plan]].
+
+### Common venting of multiple appliances shall be sized using NFPA 54 vent tables or by an engineered sizing method published by the vent or appliance manufacturer.
+
+### Common venting of Category IV equipment from different manufacturers shall not be performed without each manufacturer's written approval of the proposed configuration.
+
+## Vent Configuration Selection {toc}
+
+```datasheet
+label: Venting Configuration
+type: radio
+options:
+ - "Individually vented — one heater per vent"
+ - "Common vented — multiple heaters of same manufacturer per NFPA 54"
+ - "Direct-vent through wall — sealed combustion"
+ - "Sidewall power vent — non-condensing"
+```
+
+## Condensate Drain (Category IV) {toc}
+
+### Category IV (condensing) heaters produce acidic condensate (typical pH 3 to 5) that shall be neutralized before discharge to a sanitary drain that may contain ferrous piping, copper piping, or building materials sensitive to acidic discharge.
+
+```datasheet
+label: Condensate Handling — Category IV
+type: select
+options:
+ - "Neutralizer + gravity drain to indirect-waste receptor"
+ - "Neutralizer + condensate pump to indirect-waste receptor"
+ - "Neutralizer + gravity drain to floor drain"
+ - "Not applicable — non-condensing equipment"
+default: "Neutralizer + gravity drain to indirect-waste receptor"
+```
+
+### The Contractor shall provide a manufacturer-listed or third-party condensate neutralizer with replaceable limestone or magnesium-oxide media, sized for the maximum condensate flow rate, and shall pipe the neutralizer discharge by gravity or by an approved condensate pump to an indirect-waste receptor or floor drain per the applicable plumbing code.
+
+### Condensate piping shall be of a material chemically resistant to low-pH condensate — PVC, CPVC, polypropylene, or stainless steel — and shall not be of bare copper, brass, or carbon steel.
+
+# Fuel-Gas Connection {toc}
+
+## Fuel-gas piping to the heater shall be sized and installed per NFPA 54 / IFGC and shall comply with [[sync/fuel-gas-piping]] where that standard exists in the library.
+
+```datasheet
+label: Fuel-Gas Service to Heater
+type: select
+options:
+ - "Natural gas, low-pressure (≤ 0.5 psig at heater)"
+ - "Natural gas, elevated pressure with at-heater regulator (2 psig and above)"
+ - "Propane (LP), low-pressure (≤ 0.5 psig at heater)"
+ - "Propane (LP), elevated pressure with at-heater regulator"
+ - "Not applicable — electric, HPWH, or indirect-fired"
+default: "Natural gas, low-pressure (≤ 0.5 psig at heater)"
+```
+
+## Each heater shall be provided with a manual gas shutoff valve external to the heater jacket and within sight of the heater.
+
+## Each heater shall be provided with a sediment trap (dirt leg) downstream of the shutoff and immediately upstream of the heater inlet.
+
+## Each heater shall be provided with a union or dielectric flange between the shutoff valve and the heater for service disconnection.
+
+## Each heater shall be provided with a pressure gauge tap or test port for combustion startup.
+
+## Where the heater requires a supply pressure different from the building's distribution pressure, an in-line gas pressure regulator listed for the application shall be provided and vented per code.
+
+# Electrical Connection {toc}
+
+## Electric storage water heaters, heat-pump water heaters, controls for gas-fired heaters, power-vent fans, condensate pumps, and the recirculation pump shall be connected per NFPA 70.
+
+```datasheet
+label: Disconnect Type
+type: select
+options:
+ - "Non-fused safety switch within sight of equipment"
+ - "Fused safety switch within sight of equipment"
+ - "Circuit breaker in panelboard within sight of equipment (where permitted)"
+ - "Cord and plug connection (where permitted by code and listing)"
+default: "Non-fused safety switch within sight of equipment"
+```
+
+## Each piece of equipment shall be provided with a disconnect within sight of the equipment per NEC Article 422 (appliances) or Article 430 (motors) as applicable.
+
+## Equipment grounding and bonding for electric storage water heaters and HPWHs shall comply with [[sync/grounding-and-bonding]].
+
+## Branch-circuit conductor sizing, overcurrent protection, and the disconnect rating shall be coordinated with the equipment nameplate values and shall be [[drawing: as indicated on the electrical plans and panelboard schedules]].
+
+# Heat-Pump Water Heaters {toc}
+
+## Heat-pump water heaters (HPWHs) extract heat from ambient air and reject it into the stored water, achieving COP values of approximately 2 to 4 depending on ambient conditions. {note}
+
+```datasheet
+label: HPWH Source-Air Configuration
+type: select
+options:
+ - "Ambient air drawn from mechanical room (room must be sized adequately)"
+ - "Ducted from outside — supply and return ducts"
+ - "Ducted from outside — supply duct only with mechanical-room exhaust"
+ - "Split-system with outdoor compressor and indoor storage tank"
+ - "Not applicable — not HPWH"
+default: "Ambient air drawn from mechanical room (room must be sized adequately)"
+```
+
+```datasheet
+label: HPWH Backup Heat Source
+type: select
+options:
+ - "Integral electric-resistance backup (factory-installed)"
+ - "No backup — HPWH only, sized for full load"
+ - "Separate backup heater piped in series or parallel"
+ - "Not applicable — not HPWH"
+default: "Integral electric-resistance backup (factory-installed)"
+```
+
+```datasheet
+label: HPWH Maximum Sound Level at 3 ft
+type: range
+unit: dBA
+options:
+ min: 40
+ max: 75
+ step: 1
+default: 55
+```
+
+## The HPWH source-air space shall be sized large enough to avoid driving the supply ambient below the unit's minimum operating temperature.
+
+## HPWH condensate generated by dehumidification of the source air shall be piped to a drain.
+
+## HPWH sound levels are higher than for resistance electric or gas-fired storage equipment and shall be evaluated against adjacent occupied spaces.
+
+## Refrigerant safety per UL 60335-2-40 governs the maximum allowable refrigerant charge for the installation environment, particularly for units using A2L refrigerants.
+
+# Temperature Setpoints and Legionella Control {toc}
+
+## Storage Temperature {toc}
+
+### Storage temperature shall be set in accordance with ASHRAE 188 to inhibit Legionella pneumophila multiplication.
+
+```datasheet
+label: Storage Temperature Setpoint
+type: select
+unit: °F
+options:
+ - "140°F — ASHRAE 188 standard"
+ - "135°F — ASHRAE 188 acceptable (lower limit of recommended range)"
+ - "150°F — enhanced thermal disinfection (healthcare common)"
+ - "160°F — high-temperature pasteurization service"
+default: "140°F — ASHRAE 188 standard"
+```
+
+### Legionella grows in the range of approximately 68°F to 122°F; storing water above 140°F provides reliable thermal disinfection of the storage volume, and storing above 122°F substantially reduces growth. {note}
+
+### Storage at 140°F or above is the standard recommendation for ASHRAE 188 compliance.
+
+### Healthcare facilities subject to NFPA 99 and applicable state health department requirements typically require storage at 140°F or higher with documented operational temperature logging.
+
+## Distribution Temperature {toc}
+
+### Distribution temperature downstream of the master mixing valve shall be maintained at or above 120°F to keep the entire recirculation loop above the Legionella growth range while delivering water at a temperature that does not require fixture-level scald protection beyond the point-of-use temperature-limiting devices specified in [[sync/plumbing-fixtures]].
+
+```datasheet
+label: Distribution Temperature Setpoint (Mixing Valve Outlet)
+type: select
+unit: °F
+options:
+ - "120°F — ASHRAE 188 standard"
+ - "124°F — enhanced Legionella control"
+ - "115°F — only where every fixture has ASSE 1070 point-of-use control"
+default: "120°F — ASHRAE 188 standard"
+```
+
+### Distribution at lower temperatures may be approved where every fixture is served by an ASSE 1070 point-of-use device set to deliver water at the fixture, and where the recirculation return temperature is documented to remain above 110°F under all operating conditions.
+
+## Master Mixing Valve {toc}
+
+### A master mixing valve conforming to ASSE 1017 shall be installed immediately downstream of the water heater(s) or supplemental storage to blend stored water (140°F or higher) with cold water to deliver the distribution setpoint (typically 120°F) to the building.
+
+```datasheet
+label: Master Mixing Valve — ASSE 1017
+type: select
+options:
+ - "Single ASSE 1017 valve sized for the design flow range"
+ - "Parallel ASSE 1017 valves with sequenced isolation for wide turndown"
+ - "ASSE 1017 with digital electronic mixing control and sensor feedback"
+default: "Single ASSE 1017 valve sized for the design flow range"
+```
+
+```datasheet
+label: Master Mixing Valve — Body Material
+type: radio
+options:
+ - "Bronze body, brass trim, NSF 61/372"
+ - "Stainless steel body, NSF 61/372"
+default: "Bronze body, brass trim, NSF 61/372"
+```
+
+### The mixing valve shall be selected with a turndown ratio sufficient to maintain accurate outlet temperature at the minimum recirculation flow rate during low-demand periods, and shall not be undersized such that the minimum draw exceeds its low-flow accuracy band.
+
+### Where the minimum flow exceeds the maximum capacity of a single ASSE 1017 valve, multiple valves shall be piped in parallel with isolation valves to permit one valve to operate during low demand and additional valves to bring online as flow increases.
+
+## Point-of-Use Temperature Limiting {toc}
+
+```datasheet
+label: Point-of-Use Temperature-Limiting Coverage
+type: radio
+options:
+ - "All public lavatories, handwash stations, showers, and school/healthcare fixtures"
+ - "Only fixtures where required by code (typical commercial baseline)"
+ - "Project-specific scope per [[sync/plumbing-fixtures]]"
+default: "All public lavatories, handwash stations, showers, and school/healthcare fixtures"
+```
+
+### Fixtures requiring delivery temperature below the distribution setpoint — public lavatories, handwash stations, showers in any application, and any fixture in a school or healthcare facility — shall be served by an ASSE 1070 point-of-use temperature-limiting device installed at the fixture or fixture group.
+
+### Showers shall also be served by an ASSE 1016 anti-scald shower valve in addition to or in lieu of the ASSE 1070 device per the requirements of [[sync/plumbing-fixtures]].
+
+# Thermal Expansion Tank {toc}
+
+## A thermal expansion tank shall be installed on the cold-water inlet side of the water heater whenever the building is served through a backflow-preventing device — a reduced-pressure principle backflow assembly, a double-check valve, a pressure-reducing valve, or a check valve — that creates a closed system.
+
+```datasheet
+label: Thermal Expansion Tank
+type: radio
+options:
+ - "Required — closed system (backflow preventer, PRV, or check valve present)"
+ - "Not required — open system (no upstream check or backflow device)"
+default: "Required — closed system (backflow preventer, PRV, or check valve present)"
+```
+
+```datasheet
+label: Expansion Tank Diaphragm / Bladder Material
+type: radio
+options:
+ - "Potable PE-X (cross-linked polyethylene) lined bladder, NSF 61"
+ - "Butyl rubber bladder, NSF 61"
+default: "Potable PE-X (cross-linked polyethylene) lined bladder, NSF 61"
+```
+
+```datasheet
+label: Expansion Tank Acceptance Volume
+type: range
+unit: gal
+drawing_ref: true
+options:
+ min: 1
+ max: 80
+ setpoints: [1, 2, 4.4, 8.5, 14, 20, 32, 44, 62, 80]
+default: 4.4
+```
+
+## In a closed system, the expansion of water when heated cannot return upstream to the utility main, so without an expansion tank the system pressure can rise to the T&P relief valve set pressure and cause repeated relief discharge, eventually compromising the relief valve seat. {note}
+
+## The expansion tank shall be sized using the manufacturer's published method based on the storage volume, the temperature rise from cold-water supply to setpoint, and the system supply pressure.
+
+## The expansion tank pre-charge pressure shall be set equal to the system static pressure at the expansion tank's installed elevation before the tank is connected to the water side of the system.
+
+## The Contractor shall measure system static pressure and adjust pre-charge before installation, not after.
+
+# Pressure and Temperature Relief {toc}
+
+## Each storage water heater and each indirect storage tank shall be provided with a combined temperature and pressure (T&P) relief valve conforming to ANSI Z21.22 / CSA 4.4, listed for the heater's input rating in Btu/h and the tank's working pressure in psi.
+
+```datasheet
+label: T&P Relief Valve Set Pressure
+type: select
+unit: psi
+options:
+ - "75 psi"
+ - "100 psi"
+ - "125 psi"
+ - "150 psi"
+default: "150 psi"
+```
+
+```datasheet
+label: T&P Relief Valve Set Temperature
+type: radio
+unit: °F
+options:
+ - "210°F (standard)"
+default: "210°F (standard)"
+```
+
+```datasheet
+label: T&P Relief Discharge Piping
+type: select
+options:
+ - "Copper Type L, full-size, to indirect-waste receptor with air gap"
+ - "CPVC ASTM D2846, full-size, to indirect-waste receptor with air gap"
+ - "Galvanized steel, full-size, to indirect-waste receptor with air gap"
+default: "Copper Type L, full-size, to indirect-waste receptor with air gap"
+```
+
+## The T&P relief valve shall be installed in a dedicated tapping at the top of the tank or at the location specified by the manufacturer's instructions; it shall not be valved off, and the inlet shall not be reduced in size.
+
+## The discharge from the T&P relief valve shall be piped full-size by gravity to a safe location of discharge — a floor drain or an indirect-waste receptor — such that any discharge is visible to building maintenance personnel and any thermal hazard is minimized.
+
+## Discharge piping shall be of a material rated for the relief temperature (typically 210°F) and shall terminate with an air gap above the receptor.
+
+# Recirculation System {toc}
+
+## Purpose {toc}
+
+### In commercial buildings, domestic hot water must be delivered to fixtures within a time that satisfies both occupant comfort and the energy code.
+
+```datasheet
+label: Recirculation System Configuration
+type: select
+options:
+ - "Pumped return to water heater inlet (standard)"
+ - "Pumped return to a dedicated heater recirculation port"
+ - "Pumped return to a recirculation tee on the cold-water inlet (uncommon)"
+ - "Demand recirculation with point-of-use trigger"
+ - "Not applicable — no recirculation required (small system)"
+default: "Pumped return to water heater inlet (standard)"
+```
+
+### Without a recirculation system, water in long horizontal branches stagnates, cools, and creates conditions favorable to Legionella in the dead leg; the recirculation system keeps water circulating continuously or on a controlled schedule through a return loop from the distribution piping back to the water heater, maintaining the return temperature above the Legionella threshold throughout the loop. {note}
+
+### The return-loop piping itself is the scope of [[sync/domestic-water-piping]]; this standard establishes the pump, control, and balancing requirements at the equipment. {note}
+
+## Recirculation Pump {toc}
+
+### The recirculation pump shall be an in-line centrifugal pump with bronze or stainless steel wetted parts, NSF/ANSI 61 certified, sized for the recirculation flow rate and head loss determined by the Engineer.
+
+```datasheet
+label: Recirculation Pump Wetted Material
+type: radio
+options:
+ - "Bronze body and impeller (standard)"
+ - "Stainless steel body and impeller (aggressive water)"
+default: "Bronze body and impeller (standard)"
+```
+
+```datasheet
+label: Recirculation Pump Motor
+type: select
+options:
+ - "Wet-rotor permanent-magnet ECM (variable-speed, energy-efficient)"
+ - "Wet-rotor fixed-speed (standard)"
+ - "Inline centrifugal with separate motor"
+default: "Wet-rotor permanent-magnet ECM (variable-speed, energy-efficient)"
+```
+
+### The pump shall be installed with isolation valves on suction and discharge, a check valve on the discharge, unions for service removal, and a strainer on the suction where required by the manufacturer.
+
+### The pump motor shall be permanently lubricated, totally enclosed fan-cooled (TEFC) or open-drip-proof (ODP) as suitable for the mechanical-room environment, and rated for continuous duty at the design flow.
+
+## Recirculation Control {toc}
+
+### ASHRAE 90.1 requires that recirculation pumps not operate continuously when there is no demand. {note}
+
+```datasheet
+label: Recirculation Pump Control
+type: select
+options:
+ - "Aquastat + time clock combination (standard)"
+ - "Aquastat only (continuous-occupied applications)"
+ - "Time clock only (legacy; not preferred for new construction)"
+ - "Demand-based control (push-button, motion, or flow-sensor activation)"
+ - "BAS integration with scheduled operation and temperature feedback"
+default: "Aquastat + time clock combination (standard)"
+```
+
+### Control shall be by aquastat (return temperature sensor), time clock, demand-based trigger, or a combination, as required by the energy code in force and the building's operating schedule.
+
+### Combined aquastat-plus-time-clock control is the most common commercial configuration — the time clock disables the pump during unoccupied hours, and the aquastat cycles the pump within occupied hours to maintain return temperature only when needed. {note}
+
+## Recirculation Balancing {toc}
+
+### Where the recirculation loop serves multiple branches or multiple risers, balancing is required so flow is proportional to the heat loss of each branch rather than taking the path of least resistance. {note}
+
+```datasheet
+label: Recirculation Balancing Method
+type: select
+options:
+ - "Manual balancing valve at each riser/branch with memory stop and flow indicator"
+ - "Automatic pressure-independent thermostatic balancing valve at each branch"
+ - "Not applicable — single-loop system with no branches"
+default: "Manual balancing valve at each riser/branch with memory stop and flow indicator"
+```
+
+### Where the recirculation loop serves multiple branches or multiple risers, balancing valves or pressure-independent automatic balancing valves shall be provided at each branch take-off or riser base on the return circuit to ensure flow is proportional to the heat loss of each branch.
+
+### Without balancing, the shortest-path branches circulate at excess flow while the longest branches stagnate, defeating Legionella control in the dead legs. {note}
+
+### Balancing valve locations and setpoints shall be coordinated with [[sync/domestic-water-piping]] and are [[drawing: as indicated on the plumbing riser diagrams]].
+
+# Controls and Monitoring {toc}
+
+## Each water heater shall be provided with the safety and operating controls required for its equipment type and shall be integrated with the building automation system as specified below.
+
+```datasheet
+label: BAS Integration
+type: select
+options:
+ - "Monitor only — supply temperature, return temperature, pump status, alarm"
+ - "Monitor and schedule — setpoints and operating schedule from BAS"
+ - "Full BAS integration — read/write of setpoints, sequences, and diagnostics"
+ - "No BAS integration — standalone controls"
+default: "Monitor only — supply temperature, return temperature, pump status, alarm"
+```
+
+```datasheet
+label: Recirculation Return Temperature Sensor
+type: radio
+options:
+ - "Thermowell-mounted RTD with BAS input"
+ - "Thermowell-mounted thermistor with BAS input"
+ - "Surface-mount strap-on (not preferred — accuracy concerns)"
+default: "Thermowell-mounted RTD with BAS input"
+```
+
+## Each water heater shall be provided with an operating thermostat (or modulating control as applicable to the equipment), a high-temperature limit cutout, a flame safeguard (gas) or thermal cutout (electric), a low-water cutoff where required by code or by ASME CSD-1, and the manufacturer's required combustion safety controls.
+
+## The factory-supplied control package shall not be modified in the field; field-supplied controls shall be limited to those external to the appliance and shall not defeat any safety function of the factory controls.
+
+## BAS points and communication protocol shall be coordinated with [[sync/building-automation-system]].
+
+## Where the BAS provides monitoring of recirculation return temperature for Water Management Program compliance, the temperature sensor shall be installed in a thermowell at the heater inlet (return) and shall be calibrated at startup to within ±2°F of a traceable reference.
+
+# Installation {toc}
+
+## Equipment Setting {toc}
+
+```datasheet
+label: Seismic Anchorage
+type: select
+options:
+ - "Not required — SDC A or B"
+ - "Two-strap horizontal anchorage to structure (SDC C and above, standard)"
+ - "OSHPD / IAPMO pre-approved detail (high-seismic, healthcare)"
+ - "Project-specific engineered anchorage"
+default: "Not required — SDC A or B"
+```
+
+### Equipment shall be set level on a housekeeping pad or on the manufacturer's specified support.
+
+### Tank-type heaters in seismic regions shall be anchored per the project's seismic anchorage details — typically two horizontal straps (upper and lower) anchored to adjacent structure or to a strut frame, with the heater isolated from rigid contact by manufacturer-furnished or field-cut spacers where required.
+
+### Pre-approved seismic anchorage details (OSHPD, IAPMO, or AHJ-accepted) shall be used where available to avoid project-specific engineering for the anchorage.
+
+## Piping Connections {toc}
+
+```datasheet
+label: Heater Piping Connection Method
+type: radio
+options:
+ - "Unions on inlet and outlet (sizes through 2 in.)"
+ - "Flanged connections on inlet and outlet (sizes 2-1/2 in. and larger)"
+ - "Grooved mechanical couplings (where listed for application)"
+default: "Unions on inlet and outlet (sizes through 2 in.)"
+```
+
+### Cold-water inlet, hot-water outlet, and recirculation-return connections shall be made with unions or flanged connections (depending on size) between the heater and the building piping to permit heater service and replacement without cutting the building piping.
+
+### Each heater piping connection shall include an isolation valve.
+
+### Dielectric isolation shall be provided between the heater connections (typically copper or bronze) and any ferrous building piping per [[sync/domestic-water-piping]].
+
+### Drain valves at the tank tapping shall be full-port ball valves with female hose-thread outlets, NSF 61/372 certified, with a threaded cap on the outlet.
+
+### The Contractor shall verify that the drain valve location and the floor-drain layout permit complete drain-down of the tank without flooding.
+
+## Gauges and Thermometers {toc}
+
+### Each heater shall be provided with a pressure gauge on the inlet (cold) and a combination pressure-temperature gauge on the outlet (hot).
+
+### The mixing valve outlet shall be provided with a temperature gauge or thermometer.
+
+### The recirculation pump suction shall be provided with a temperature gauge or BAS sensor as established in Controls and Monitoring.
+
+### Gauges and thermometers shall be installed in a position visible from the front of the heater without removing covers or shields.
+
+## Labeling and Valve Tagging {toc}
+
+```datasheet
+label: Valve and Equipment Tagging
+type: radio
+options:
+ - "Engraved brass tags with chain or wire attachment (durable, preferred)"
+ - "Photo-laminated plastic tags with chain or wire attachment"
+default: "Engraved brass tags with chain or wire attachment (durable, preferred)"
+```
+
+### Each heater, mixing valve, expansion tank, recirculation pump, and isolation valve shall be labeled with a permanent engraved or photo-laminated tag indicating the equipment identifier from the equipment schedule, the service (DHW supply, DHW recirculation, etc.), and any required setpoint.
+
+### Valve tags shall be coordinated with the as-built piping schematic so a maintenance technician can identify and trace any tagged valve without ambiguity.
+
+# Testing and Startup {toc}
+
+## Pre-Startup Inspection {toc}
+
+### Before startup, the Contractor shall verify that the heater is correctly piped (inlet and outlet connections in the correct ports), that all isolation valves are open, that the tank is filled and vented of air, that the T&P relief valve is installed and the discharge piping is open and routed to a receptor, that the expansion tank pre-charge is correct, that the gas supply pressure (static) is within the heater's listed range, that the electrical disconnect is energized, that the venting is complete and unobstructed, and that the condensate drain (Category IV) is open and routed.
+
+## Startup {toc}
+
+### Startup shall be performed by a factory-authorized technician for any heater with a manufacturer-required commissioning procedure, or by a qualified plumber/mechanic where the manufacturer accepts contractor startup.
+
+### The startup procedure shall include confirmation of fuel-gas dynamic supply pressure; manifold pressure setting; combustion testing (CO, CO₂, stack temperature) at high-fire and at low-fire/lowest stable rate; verification of high-temperature cutout operation by simulated overtemperature; verification of T&P relief valve operation by manual test lever; verification of recirculation pump rotation, flow, and aquastat function; setting of storage temperature and mixing-valve outlet temperature; and recording of all setpoints and as-found / as-left values in the startup report.
+
+## Field Performance Test {toc}
+
+### Following startup, a field performance test shall be conducted to verify the items listed below.
+
+```datasheet
+label: Field Performance Test — Required Documentation
+type: checkbox
+options:
+ - "Outlet temperature at heater (storage setpoint verification)"
+ - "Outlet temperature at mixing valve (distribution setpoint verification)"
+ - "Recirculation return temperature at heater inlet"
+ - "T&P relief valve manual test"
+ - "Combustion test report (gas-fired)"
+ - "HPWH heating capacity and condensate verification"
+ - "Recirculation pump aquastat and control verification"
+ - "Expansion tank pre-charge verification"
+default: "Outlet temperature at heater (storage setpoint verification)"
+```
+
+### The field performance test shall verify outlet temperature at the heater within ±5°F of the storage setpoint after a recovery cycle from a fully drawn-down condition.
+
+### The field performance test shall verify outlet temperature downstream of the master mixing valve within ±5°F of the distribution setpoint at the design flow rate and at a minimum draw representative of nighttime recirculation-only operation.
+
+### The field performance test shall verify recirculation return temperature at the heater inlet equal to or greater than the distribution setpoint minus 10°F (typically ≥ 110°F when distribution is 120°F).
+
+### The field performance test shall verify no discharge from the T&P relief valve during normal operation, including during recovery from full draw with the expansion tank in service.
+
+### The field performance test shall verify combustion test results within the manufacturer's published range.
+
+### For HPWH, the field performance test shall verify measured heating capacity within 90 percent of the manufacturer's published capacity at the test conditions, and no condensate accumulation in the equipment cabinet.
+
+## Disinfection {toc}
+
+### The water heater and storage tank shall be disinfected as part of the building's domestic-water system disinfection per [[sync/domestic-water-piping]] before being placed in service for potable use.
+
+# Delivery, Storage, and Handling {toc}
+
+## Water-heating equipment shall be delivered to the site in the manufacturer's original packaging, with all factory protective covers, plugs, and tags in place.
+
+## Equipment shall be inspected at delivery for shipping damage; damaged equipment shall be reported in writing to the carrier and to the manufacturer's authorized representative before installation and shall not be installed without disposition.
+
+## Equipment shall be stored indoors, on level dunnage, protected from freezing, weather, construction water, and physical damage until installed.
+
+## Storage tanks and packaged heaters with factory insulation shall not be stacked.
+
+## Refrigerant-containing HPWHs shall be stored upright and shall not be tipped beyond the manufacturer's permitted shipping orientation.
+
+## Tipping a HPWH on its side can displace compressor oil and require an extended power-off settling period before startup. {note}
+
+## Vent components, gas piping, condensate piping, and small electrical components shall be stored in their original packaging, segregated from other trades' materials, and protected from foot traffic and construction dust.
+
+# Warranty {toc}
+
+## The Contractor shall procure equipment carrying the standard manufacturer's warranty for the equipment category, and the warranty period shall commence at substantial completion or per the manufacturer's published policy.
+
+```datasheet
+label: Warranty Requirement
+type: select
+options:
+ - "Manufacturer standard warranty"
+ - "Manufacturer standard + extended parts (5 years minimum)"
+ - "Manufacturer standard + extended parts and labor (5 years minimum)"
+ - "Project-specified warranty per equipment schedule"
+default: "Manufacturer standard warranty"
+```
+
+## Standard commercial warranties typically include: tank (storage water heaters) 3 to 10 years; heat exchanger (gas-fired) 5 to 15 years; compressor (HPWH) 5 to 10 years; all other components 1 year parts. {note}
+
+## Where extended warranties or labor coverage are required by the contract documents, the requirement shall be stated explicitly in the equipment schedule and shall be documented in the closeout submittals.
+
+## Warranty exclusions for water chemistry outside the manufacturer's stated acceptable range shall be acknowledged by the Owner in the project documents.
+
+# Spare Parts {toc}
+
+## The Contractor shall deliver to the Owner at substantial completion the following spare parts, marked with the equipment identifier and stored in a labeled container in the mechanical room or in a location designated by the Owner.
+
+- One complete set of replacement gaskets for each unique heater connection and each unique mixing valve
+- One spare sacrificial anode rod for each glass-lined tank
+- One spare T&P relief valve per unique set pressure / set temperature combination
+- One spare recirculation pump cartridge or pump head (for cartridge-style wet-rotor pumps) per unique pump model
+- One spare expansion tank diaphragm assembly per unique expansion tank model (where field-replaceable)
+- One spare aquastat or temperature controller per unique model
+- For Category IV equipment, one spare condensate-neutralizer media charge
+
+```datasheet
+label: Spare Parts Delivery
+type: checkbox
+options:
+ - "Replacement gaskets for heater and mixing valve connections"
+ - "Spare sacrificial anode rod (one per glass-lined tank)"
+ - "Spare T&P relief valve (one per unique set pressure)"
+ - "Spare recirculation pump cartridge or pump head"
+ - "Spare expansion tank diaphragm assembly (field-replaceable models)"
+ - "Spare aquastat or temperature controller"
+ - "Spare condensate-neutralizer media (Category IV)"
+default: "Replacement gaskets for heater and mixing valve connections"
+```
+
+## The Contractor shall deliver the spare parts listed above to the Owner at substantial completion, marked with the equipment identifier and stored in a labeled container in the mechanical room or a location designated by the Owner.