1 Scope
NOTE This specification covers the materials, fabrication, installation, testing, and commissioning of closed-loop hydronic piping systems within commercial, institutional, and industrial buildings. (1.1)
NOTE The systems addressed include heating hot water (HHW), chilled water (CHW), and condenser water (CW) distribution, including the supply and return mains, risers, runouts, terminal unit connections, and all associated components — valves, strainers, expansion devices, air separators, expansion tanks, flexible connectors, and insulation. (1.2)
NOTE Hydronic piping is the circulatory system of the building's HVAC plant. (1.3)
NOTE It moves thermal energy between central equipment — boilers, chillers, cooling towers, heat exchangers — and the terminal equipment that conditions occupied spaces. (1.4)
NOTE Because the system is entirely closed and recirculating, the quality, cleanliness, and chemistry of the system water profoundly affects the long-term integrity of all piping, valves, and equipment surfaces. (1.5)
NOTE This standard addresses not only the structural installation of the piping system but the entire commissioning sequence — flushing, chemical treatment, and testing — that determines whether the system will operate reliably over its service life. (1.6)
1.7 The work shall comply with ASME B31.9, Building Services Piping, the adopted edition of the International Mechanical Code (IMC) Chapter 12, and all applicable provisions of the local Authority Having Jurisdiction.
1.8 The boundary of work under this standard is the piping and piping specialties from the flanged or mechanical-joint connections at central plant equipment through all distribution piping to the flanged or union connections at terminal heating and cooling coils, fan-coil units, heat exchangers, and induction units.
NOTE Terminal unit equipment itself is not covered; coordinate equipment requirements with
Air Handling Units and relevant equipment standards.
(1.9) NOTE Pumps and pump sets are covered in
Hvac Pumps, variable frequency drives on pump motors in
Hvac Variable Frequency Drives, and water treatment chemical programs in
Hvac Water Treatment; this standard covers the physical flushing, fill, and initial treatment that places the system in condition to receive the chemical treatment program.
(1.10) 2 Referenced Standards
2.1 Equipment, materials, and installation shall comply with the latest adopted editions of the following standards.
| Standard |
Title |
| ASME B31.9 |
Building Services Piping |
| ASME B16.9 |
Factory-Made Wrought Buttwelding Fittings |
| ASME B16.11 |
Forged Fittings, Socket-Welding and Threaded |
| ASME B16.21 |
Nonmetallic Flat Gaskets for Pipe Flanges |
| ASME B16.22 |
Wrought Copper and Copper Alloy Solder-Joint Pressure Fittings |
| ASME B16.24 |
Cast Copper Alloy Pipe Flanges, Flanged Fittings, and Valves |
| ASME B16.25 |
Buttwelding Ends |
| ASME B16.34 |
Valves — Flanged, Threaded, and Welding End |
| ASME Sec. IX |
Boiler and Pressure Vessel Code — Welding and Brazing Qualifications |
| ASTM A53 |
Seamless and Welded Steel Pipe |
| ASTM A106 |
Seamless Carbon Steel Pipe for High-Temperature Service |
| ASTM A234 |
Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service |
| ASTM B88 |
Seamless Copper Water Tube |
| ASTM B88M |
Seamless Copper Water Tube (Metric) |
| ASTM C534 |
Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form |
| ASTM C553 |
Mineral Fiber Blanket Thermal Insulation for Commercial and Industrial Applications |
| ASTM C585 |
Inner and Outer Diameters of Rigid Thermal Insulation for Nominal Sizes of Pipe and Tubing |
| ASTM C1290 |
Flexible Fibrous Glass Pipe Insulation |
| AWS A5.8 |
Specification for Filler Metals for Brazing and Braze Welding |
| ANSI/ASHRAE/IES 90.1 |
Energy Standard for Buildings Except Low-Rise Residential Buildings |
| IMC |
International Mechanical Code, Chapter 12 (Hydronic Piping) |
| MSS SP-58 |
Pipe Hangers and Supports — Materials, Design, Manufacture, Selection, Application, and Installation |
| SMACNA |
HVAC Systems — Duct Design (for system coordination) |
| NFPA 13 |
Standard for the Installation of Sprinkler Systems (for system separation) |
2.2 Where the contract documents, the adopted building code, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
3 Submittals
3.1 Action Submittals
NOTE The action submittals required for the Engineer's review and return before procurement and installation are the product data, drawings, qualification records, and plans listed below. (3.1.1)
- Product data sheets for all pipe materials, including manufacturer, standard designation, wall schedule or type, pressure rating, and service temperature range, for each service (HHW, CHW, CW) and each pipe size range covered
- Product data sheets for all fitting types, showing material, applicable ASME standard, pressure class, and compatible pipe schedule
- Product data sheets and dimensional drawings for all valves — isolation, balancing, control, check, pressure relief, pressure-reducing, and butterfly — with pressure and temperature ratings, Cv values for control valves, and end connection details
- Product data sheets for grooved mechanical couplings and fittings where used, including the gasket material and pressure rating by service
- Product data sheets for flexible pipe connectors (pump connections and equipment connections), with pressure rating and movement capability
- Product data sheets for air separators, combination air separator/dirt separator units, and automatic air vents, with ratings and connection sizes
- Product data sheets for expansion tanks, with pre-charge pressure, acceptance volume, total volume, and design working pressure
- Product data sheets for dielectric unions and dielectric fittings where used
- Pipe hanger and support catalog cuts, with hanger types per MSS SP-58 designation, rod and beam clamp ratings, and thermal insulation shield details for insulated lines
- Pipe insulation product data, showing thermal conductivity (k-factor) at the specified mean temperature, moisture vapor permeability, facing description, and applicable ASTM standards
- A hydronic piping coordination drawing set showing routing, pipe sizes, support locations, anchor and guide locations, expansion loop or expansion joint locations, valve locations, and equipment connection details. Coordination drawings shall be at a scale sufficient to resolve conflicts with structural members, conduit, duct, and other mechanical piping before rough-in. Coordinate with Hvac Ductwork and Raceways And Conduit spatial envelopes
- Welding and brazing procedure specifications (WPS) and procedure qualification records (PQR) per ASME Section IX for all butt-weld and brazed joints, where required by ASME B31.9
- Welder and brazer qualification records for all personnel who will perform work on this project
- A written pressure test plan describing the test boundaries, test medium, test pressure, test duration, pressure gauges to be used, method of isolation, and the sequence of testing that allows progressive testing before systems are insulated
- A written flushing and cleaning plan describing the sequence, temporary piping or bypass arrangements, flush velocity requirements, flush duration, sample collection method, and acceptance criteria
- Chemical treatment start-up plan coordinated with Hvac Water Treatment
☑ Pipe material product data by service and size
☐ Fitting product data by type and pressure class
☐ Valve product data (isolation, balancing, control, check, PRV)
☐ Grooved coupling product data (where used)
☐ Flexible connector product data
☐ Air separator and automatic air vent product data
☐ Expansion tank product data
☐ Pipe hanger and support product data
☐ Pipe insulation product data
☐ Hydronic piping coordination drawings
☐ Welding/brazing procedure and qualification records
☐ Pressure test plan
☐ Flushing and cleaning plan
☐ Chemical treatment start-up plan
3.1.2 The Contractor shall submit the action submittals listed above for the Engineer's review and return before procurement and installation.
3.1.3 Work on each system shall not proceed until the corresponding submittals are returned.
3.1.4 Submittals shall be complete and coordinated across all system components before any item is submitted; piecemeal submittals that require multiple resubmissions due to internal inconsistency will not be accepted.
3.2 Closeout Submittals
NOTE The closeout submittals required at substantial completion before the hydronic systems are accepted are the reports, drawings, schedules, and records listed below. (3.2.1)
- Signed and dated pressure test reports for all systems, with measured pressure, test duration, observed pressure drop, and pass/fail determination
- Signed and dated flushing reports documenting the flush velocity achieved, flush duration, water clarity before and after flushing, and particle count or turbidity measurement if specified
- Initial chemical treatment reports documenting the water treatment chemical added, dosage, initial chemistry results (pH, inhibitor concentration, conductivity), and the baseline reading established for the ongoing treatment program
- As-built piping drawings reflecting the actual installed routing, all valve numbers, hanger locations, anchor and guide locations, and expansion device locations
- Valve tag schedule correlating each valve tag number to its system, service, size, type, normal position (open/closed), and location description
- Operation and maintenance manuals for all specialty items — expansion tanks, air separators, strainers, balancing valves, pressure-reducing valves, and pressure relief valves — including scheduled maintenance intervals and procedures
- Record of all welding and brazing, including the joint number, welder/brazer identification, procedure used, and inspection result
☑ Signed and dated pressure test reports for all systems
☐ Signed and dated flushing reports
☐ Initial chemical treatment reports with baseline chemistry
☐ As-built piping drawings
☐ Valve tag schedule
☐ Operation and maintenance manuals for all specialty items
☐ Record of all welding and brazing
3.2.2 At substantial completion, the Contractor shall provide the closeout submittals listed above before the hydronic systems are accepted.
4 Quality Assurance
4.1 Code Compliance
4.1.1 All piping work shall comply with ASME B31.9, Building Services Piping, including its requirements for design, materials selection, fabrication, installation, examination, and testing.
4.1.2 Where ASME B31.9 defers to other codes (for example, ASME Section IX for welder qualification), those referenced codes shall be followed.
4.1.3 The Contractor shall maintain a copy of ASME B31.9 at the project site throughout installation and shall make it available for inspection.
4.2 Welder and Brazer Qualifications
4.2.1 Personnel performing welded or brazed pipe joints shall be qualified under ASME Section IX for the procedure, position, and pipe schedule being welded or brazed.
4.2.2 Welder and brazer qualification records shall be available at the site.
4.2.3 Where a welder or brazer has not performed qualified work within six months, requalification shall be required before that person performs production work on this project.
4.2.4 The Contractor shall not allow unqualified personnel to make production joints under any circumstances; rework of joints made by unqualified personnel is at the Contractor's expense.
4.3 Examination of Welds
4.3.1 Welded joints in steel piping shall be visually examined in accordance with ASME B31.9 after each joint is completed and before the joint is buried, covered by insulation, or otherwise made inaccessible.
4.3.2 Visual examination shall confirm that the weld is full profile, free of cracks, undercut, overlap, and surface porosity, and that the weld smoothly transitions to the base metal on each side.
4.3.3 Random radiographic or ultrasonic examination shall be performed where called for by ASME B31.9 based on the system operating conditions, or as specified by the Engineer of Record.
4.3.4 Unacceptable welds shall be repaired or cut out and re-welded, and repair welds shall be re-examined.
4.4 Brazed Joint Quality
4.4.1 Brazed joints shall be made by qualified brazers using the approved brazing procedure.
4.4.2 On completion, each brazed joint shall show a uniform fillet of brazing filler metal around the entire circumference of the socket joint, with the filler metal visible at the socket mouth.
4.4.3 Joints that show voiding, incomplete fill, or incomplete flow of filler metal shall be re-made.
4.5 Installer Qualifications
4.5.1 The Contractor performing hydronic piping work shall have a minimum of five years of documented experience installing commercial HVAC hydronic piping systems of similar scope and complexity.
4.5.2 The Contractor's supervision shall include at least one individual who has completed a recognized mechanical contractor apprenticeship program or holds a current journeyman license in the applicable jurisdiction.
4.6 Single-Source Responsibility for Grooved Systems
4.6.1 Where mechanical grooved coupling systems are used, all grooved couplings, fittings, gaskets, and grooving tools for a given pipe size and service shall be products of a single manufacturer to ensure geometric compatibility and consistent gasket compression.
4.6.2 Mixing grooved coupling components from different manufacturers is not permitted.
5 Environmental and Service Conditions
5.1 System Design Parameters
5.1.1 The design operating conditions governing material selection, pressure class, and hanger spacing shall be as indicated on the contract drawings for each system.
5.1.2 The datasheet fields below record the project-specific operating parameters; they shall be completed by the Engineer of Record before the standard is issued for construction.
120250
120140160180200210250
Default: 180 °F
30160
305075100125150160
Default: 125 psig
3655
40424445485055
Default: 44 °F
30150
305075100125150
Default: 100 psig
65100
6575859095100
Default: 85 °F
30150
305075100125150
Default: 75 psig
5.1.3 The maximum allowable operating pressure (MAOP) established on the drawings governs; the Contractor shall not select pipe schedule, valve pressure class, or fitting pressure class for a lower MAOP than shown.
5.2 Freeze Protection
5.2.1 The freeze protection method shall be selected and confirmed on the contract drawings, recorded in the datasheets below.
○ Glycol solution — concentration per design
○ Self-regulating electric heat trace with insulation
○ System drained seasonally (no freeze protection piping required)
● Not required — system entirely within conditioned or heated spaces
● Propylene glycol (food-grade compatible, recommended for most systems)
○ Ethylene glycol (higher heat-transfer efficiency, restricted from potable contact)
2050
202530354050
Default: 30 % (by volume)
5.2.2 Where any portion of hydronic piping is installed in unheated spaces, parking structures, exterior tunnels, or locations exposed to ambient temperatures below 35°F, freeze protection shall be provided.
5.2.3 Glycol addition shall be the primary freeze protection method for most applications; heat trace with insulation is acceptable for short runs or where glycol is incompatible with the connected equipment.
5.2.4 CHW and condenser water systems that are drained seasonally or that have sections exposed to freezing conditions shall be evaluated and the protection method confirmed on the drawings.
NOTE Freeze protection for HHW systems typically does not require glycol because the boilers maintain system temperature. (5.2.5)
5.2.6 The Engineer shall confirm the design glycol concentration based on the local design freeze temperature with at least a 10°F safety margin, and the actual required freeze protection shall govern over the default.
NOTE A glycol concentration of 30% propylene glycol provides freeze protection to approximately 0°F and is appropriate for most conditioned-building applications; higher concentrations reduce heat-transfer efficiency and increase pump energy. (5.2.7)
6 Piping Materials by Service
6.1 General Material Selection Principles
NOTE The choice between steel and copper for a given service and size range is driven by pressure-temperature requirements, installation labor practices, the local contractor market, and the available fittings and joining equipment. (6.1.1)
NOTE Steel butt-welded systems are standard for large-diameter work (generally 2½ in. and above) because welded joints are strong, fully restrained, and free-draining. (6.1.2)
NOTE Copper is standard for small-diameter work (generally 2 in. and below) in commercial buildings because brazed and solder-joint copper systems are leak-resistant and require no hot-work permits in many jurisdictions. (6.1.3)
NOTE Grooved mechanical coupling systems offer a no-hot-work alternative for steel pipe at medium-to-large diameters and are widely used on projects where open flame is restricted. (6.1.4)
6.1.5 Pipe material shall be selected by service, operating pressure, temperature, and size in accordance with ASME B31.9 and as further specified in this section.
6.1.6 Where a range of sizes spans more than one material option, the break point in sizes shall be as noted.
6.1.7 All pipe shall be new, free of rust, scale, excessive mill scale, pits, and cracks, and shall bear the required standard marking; reconditioned, used, or salvaged pipe is not permitted.
6.2 Steel Pipe — Heating Hot Water
● ASTM A53 Grade B, seamless or ERW
○ ASTM A106 Grade B, seamless
Schedule 40 (all sizes)
Schedule 40 through 2 in.; Schedule 40 or standard weight above 2 in.
Schedule 80 (high-pressure applications above 125 psig)
Per drawings
6.2.1 Black carbon steel pipe shall be used for heating hot water service in sizes 2½ in. and above, and is permitted in sizes 2 in. and below where the Contractor elects to use steel throughout for coordination or preference.
NOTE ASTM A53 Grade B and ASTM A106 Grade B are both suitable for heating hot water service within ASME B31.9 pressure and temperature limits. (6.2.2)
6.2.3 ASTM A106 Grade B seamless shall be used for service temperatures above 400°F or where a seamless product is required by the designer for all sizes; ASTM A53 Grade B ERW is suitable for the temperature ranges typical of commercial HHW systems (up to 250°F).
NOTE Schedule 40 is the standard wall for most commercial HHW applications. (6.2.4)
6.2.5 Schedule 80 shall be used where the design operating pressure exceeds 125 psig and the Engineer of Record specifies heavier wall, or where the contract drawings call for it.
6.2.6 Galvanized steel pipe shall not be used for HHW, CHW, or CW closed-loop services and is not permitted in any closed-loop system under this standard.
NOTE Galvanizing releases zinc into the system water, which at elevated temperatures can flake and plate out on heat-transfer surfaces, degrades corrosion inhibitor programs, and is incompatible with aluminum alloy components. (6.2.7)
6.3 Steel Pipe — Chilled Water and Condenser Water
● ASTM A53 Grade B, seamless or ERW
○ ASTM A106 Grade B, seamless
● Schedule 40
○ Schedule 80 (high-pressure applications)
Per drawings
6.3.1 Black carbon steel pipe shall be used for chilled water and condenser water service in sizes 2½ in. and above.
NOTE For chilled water and condenser water, the system operating temperatures are moderate (40°F to 100°F) and ASTM A53 Grade B is fully adequate for the thermal conditions. (6.3.2)
6.3.3 All CHW steel piping shall be insulated with vapor retarder facing; any joint, fitting, valve, or hanger that creates a thermal bridge or a gap in the vapor retarder is a condensation risk and shall be addressed during installation.
NOTE The primary concern for chilled water steel pipe is external condensation if insulation is breached and the surface temperature drops below the dew point, which accelerates external corrosion. (6.3.4)
6.4 Copper Tube — All Services, Small Diameter
● Type L (medium wall) — standard for all hydronic services
○ Type K (heavy wall) — where exposed to mechanical damage, underground, or per design
○ Type M (light wall) — not permitted for hydronic services under this standard
6.4.1 Drawn-temper copper tube shall be used for all hydronic services — HHW, CHW, and CW — in sizes 2 in. and below, and is permitted in sizes up to and including 4 in. where the Engineer elects to use copper throughout a building's above-ceiling distribution.
6.4.2 Copper tube shall conform to ASTM B88, and Type L shall be the standard for all hydronic applications.
6.4.3 Type M light-wall copper shall not be used for hydronic heating, chilled water, or condenser water service and is not permitted under this standard, because its reduced wall thickness provides inadequate corrosion margin in closed systems.
6.4.4 Type K shall be used where the contract drawings specify it, for any buried or embedded segments, or where the pipe is exposed to physical damage.
6.4.5 Hard-drawn (drawn-temper) tube shall be used throughout; soft-temper (annealed) tube shall not be used for in-wall or in-ceiling runs.
6.5 Pipe Size Selection
3/4 in.
1 in.
1-1/4 in.
1-1/2 in.
Per drawings
6.5.2 The Contractor shall not substitute smaller pipe sizes for those shown, regardless of velocity or pressure drop calculations, without written approval of the Engineer of Record.
6.5.3 Pipe sizing is a system design decision that accounts for pump selection, balancing, future expansion, and noise criteria; field substitution of smaller pipe sizes is a common source of system under-performance and noise complaints and shall not occur.
7 Joining Methods
7.1 General
7.1.1 Joining method shall be selected based on pipe material, pipe size, service, and the availability of open flame or hot-work permits in the project area.
7.1.2 All joining methods shall be qualified under the applicable ASME standard.
7.1.3 Mixing of incompatible joining methods — for example, using mechanical press-fit fittings on a butt-weld main — shall be performed only at rated transitions and with appropriate adapters.
7.2 Butt Welding — Steel Pipe, 2½ in. and Larger
○ SMAW (shielded metal arc welding)
○ GTAW (gas tungsten arc welding)
○ GMAW (gas metal arc welding)
● Per qualified WPS — method per Contractor's qualification
7.2.1 Steel pipe in sizes 2½ in. and larger shall be joined by butt welding in accordance with ASME B31.9 and qualified under ASME Section IX.
7.2.2 Butt-welded joints shall use beveled ends prepared per ASME B16.25.
7.2.3 Tack welding shall be done by qualified welders using the same procedure as the production weld.
7.2.4 Root passes shall be fully penetrating, and full-penetration welds shall be verified during visual examination.
7.2.5 Steel pipe flanges, when used for equipment connections and for valves requiring access, shall conform to ASME B16.5 or ASME B16.47 at the appropriate pressure class.
7.3 Socket Welding and Threaded — Steel Pipe, 2 in. and Below
● Socket welded throughout
○ Threaded throughout
○ Socket welded mains; threaded runouts at terminal units
○ Grooved mechanical coupling (no-flame alternative)
7.3.1 Steel pipe in sizes 2 in. and below may be joined by socket welding using ASME B16.11 socket-weld fittings and couplings.
7.3.2 Socket-weld joints shall be spaced with the pipe end set back approximately 1/16 in. from the bottom of the socket to allow for thermal expansion during the weld and to avoid cracking during service thermal cycling.
7.3.3 Threaded joints in steel piping shall use ASME B16.11 threaded fittings and shall be sealed with PTFE tape or anaerobic thread sealant listed for hydronic service; threading compound containing red or white lead is not permitted.
7.4 Grooved Mechanical Coupling — Steel Pipe
EPDM — heating hot water up to 230°F and chilled water
Nitrile (Buna-N) — condenser water and low-temperature HHW
Silicone — heating hot water above 230°F
7.4.1 Grooved mechanical couplings are an approved joining method for steel pipe in all sizes where the pipe material and wall thickness are compatible with roll-grooving.
7.4.2 Grooved joints shall use standard rigid couplings on straight runs to maintain pipe alignment, and flexible (deflection-capable) couplings only where the manufacturer's installation instructions allow their use and where the Engineer of Record has specifically located them for vibration isolation, seismic flexibility, or expansion accommodation.
7.4.3 The use of flexible couplings on long horizontal runs as an economical substitute for expansion compensation is not permitted, because flexible couplings at high density without proper guides allow random pipe movement that eventually fatigues the coupling gaskets.
7.4.4 Where the system contains glycol, the gasket manufacturer shall confirm compatibility with the glycol type and concentration selected.
NOTE Gasket material selection is critical because the gasket is the pressure boundary of the joint; EPDM is the most common choice for HHW and CHW, Nitrile is used for condenser water for its superior resistance to oil contamination, and EPDM is compatible with propylene and ethylene glycol solutions at normal hydronic concentrations. (7.4.5)
7.5 Brazing — Copper Tube
● BCuP series (phosphorus-copper) — copper-to-copper joints, no flux required
○ BAg series (silver alloy) — copper-to-brass and all dissimilar metal joints, flux required
● Required on all copper brazed joints
○ Required on HHW and CHW; not required on CW open-circuit segments
7.5.1 Copper tube joints shall be brazed using the socket-type wrought copper fittings of ASME B16.22 or cast copper alloy fittings.
7.5.2 Brazing filler metal shall conform to AWS A5.8 and shall be a silver-bearing alloy of the BCuP or BAg series appropriate to the joint configuration and the service temperature.
7.5.3 Cadmium-bearing brazing filler metals shall not be used.
7.5.4 Phosphorus-bearing filler metals (BCuP series) may be used on copper-to-copper joints without flux; flux shall be used for all copper-to-brass joints and for all silver alloy (BAg series) filler metals.
7.5.5 Flux residue shall be completely removed after brazing by washing with hot water, because flux is hygroscopic and mildly corrosive and, if left in place, will attack the joint over time.
7.5.6 During brazing, the inside of the tube shall be purged with dry nitrogen flowing at a low rate to prevent the formation of copper oxide scale (cuprite) on the interior surface.
7.5.7 Nitrogen purge during brazing is mandatory for this standard; a nitrogen purge fitting shall be inserted at the upstream end of each active brazing section and maintained until each joint cools below 300°F.
NOTE Interior oxide scale is a contaminant that flakes off under system flow and carries through the system to foul strainers, coil passages, and control valve seats. (7.5.8)
7.6 Solder Joints — Not Permitted for Hydronic Services Under This Standard
7.6.1 Solder (soft solder) joints using tin-lead or lead-free tin-based alloys are not permitted for any hydronic service under this standard.
7.6.2 All small-diameter copper joints shall be brazed.
NOTE Solder joints have significantly lower temperature and pressure ratings than brazed joints, and the solder alloy is susceptible to attack by aggressive water chemistry. (7.6.3)
7.7 Dielectric Isolation
● Yes — provide dielectric unions or flanges at every dissimilar metal connection
○ No — system is all-steel or all-copper (no dissimilar metal joints)
7.7.1 Where copper piping connects to steel piping or to equipment with steel or cast-iron bodies, dielectric isolation fittings shall be installed to prevent galvanic corrosion.
7.7.2 Dielectric unions shall be used in sizes 2 in. and below; dielectric flanges shall be used in sizes 2½ in. and above.
7.7.3 Dielectric fittings shall be rated for the system operating pressure and temperature.
7.7.4 The internal barrier of the dielectric fitting shall be verified to be intact and undamaged at installation; dielectric fittings with cracked or damaged barriers shall be rejected.
8 Fittings
8.1 Steel Fittings — Butt Weld
● ASME B16.9, ASTM A234 WPB
Per drawings
8.1.1 Butt-weld fittings for steel pipe in sizes 2½ in. and larger shall conform to ASME B16.9 (factory-made wrought fittings) and shall be of the same or higher pipe schedule as the connecting pipe.
8.1.2 Fitting material shall be ASTM A234 WPB or equivalent.
8.1.3 Reducing fittings shall be eccentric reducers on horizontal runs carrying liquid (flat on top to avoid air pockets in supply piping) and concentric reducers on vertical runs.
8.1.4 Miter elbows cut from straight pipe are not permitted.
8.2 Steel Fittings — Socket Weld and Threaded
8.2.1 Socket-weld and threaded fittings for steel pipe in sizes 2 in. and below shall conform to ASME B16.11 and shall be forged steel Class 3000 for socket-weld connections and Class 2000 for threaded connections, unless the system design pressure requires Class 6000, which shall be specified on the drawings.
8.2.2 Cast iron threaded fittings shall not be used on hydronic systems.
8.3 Copper Fittings
8.3.1 Wrought copper solder-joint fittings shall conform to ASME B16.22, and cast copper alloy fittings for solder-joint use shall conform to ASME B16.18.
8.3.2 All copper fittings shall be rated for the system operating pressure.
8.3.3 Rolled or drawn elbows cut from copper tube are not permitted; fittings shall be the formed, socket-type fittings meeting the applicable ASME standard.
8.4 Branch Connections
8.4.1 Branch connections in steel pipe shall be made using full-size tee fittings per ASME B16.9, reducing-outlet tee fittings, or listed welding-outlet fittings (weld-o-lets, branch-o-lets) for openings in the run pipe where a tee fitting is not available in the size combination required.
8.4.2 Fabricated branch connections formed by cutting a hole in the run pipe and welding a straight-pipe nipple without a listed outlet fitting are not permitted.
8.4.3 In copper tube, branch connections shall be made using wrought tee fittings; mechanical tee fittings (press-in-seat type) are acceptable only where rated for the system service and listed for the pipe OD.
9 Valves
9.1 Isolation Valves — General
● Full-port ball valve, bronze body, threaded or solder-joint ends
○ Full-port ball valve, stainless steel trim, threaded or solder-joint ends
○ Gate valve, bronze, threaded (not recommended for frequent operation)
Butterfly valve, grooved or lugged, EPDM seat, ductile iron or cast iron body
Butterfly valve, wafer pattern, for flanged connections
Gate valve, flanged, cast iron or ductile iron body
Ball valve, full-port, flanged, cast iron body
● Bronze stem, EPDM seat (up to 230°F)
○ Stainless steel stem, high-temperature EPDM or PTFE seat (up to 250°F)
9.1.1 Isolation valves shall be provided at all locations shown on the contract drawings and at any additional locations required to permit isolation of each major equipment item, each riser, each branch serving more than two terminal units, each side of each piece of central plant equipment, and each terminal unit or coil.
9.1.2 Isolation valves shall have bubble-tight shutoff at full system operating pressure.
9.1.3 Valve body material, end connections, and pressure rating shall match the system pipe material, size, and design pressure.
NOTE Ball valves are preferred for isolation service in sizes 2 in. and below because they are quarter-turn, provide positive visual indication of open/closed position, and maintain reliable bubble-tight shutoff through many operating cycles; butterfly valves are the standard isolation valve for sizes 2½ in. and above in commercial hydronic work. (9.1.4)
9.2 Balancing Valves
● Manual circuit setter with calibrated Cv ports (standard commercial application)
○ Automatic flow-limiting valve (pressure-independent, where specified)
○ Combination balancing and shutoff valve
9.2.1 A manual balancing valve with integral readout ports shall be provided at each terminal unit return connection and at each branch return as indicated on the contract drawings.
9.2.2 Balancing valves shall allow setting and locking a calibrated flow position and shall provide differential pressure readout ports compatible with the balancing instrument used by the Test, Adjust, and Balance (TAB) contractor.
9.2.3 The TAB contractor shall read actual flow using the valve's factory-certified Cv-versus-position curve and a differential pressure meter.
9.2.4 Balancing valves shall have a memory stop feature so they can be fully closed for service and returned to the precisely set balance position without recalibration.
9.2.5 Pressure-independent control valves (PICVs) that combine flow-limiting, balancing, and two-way control valve functions in a single body are acceptable where specified on the contract drawings.
9.2.6 Where PICVs are used, separate manual balancing valves are not required at those terminal unit locations, but isolation valves on both supply and return are still required for equipment service, and PICV specifications shall be coordinated with the control system contractor.
9.3 Check Valves
● Silent (spring-loaded) check valve, bronze or cast iron body
○ Swing check valve, flanged, cast iron body (horizontal runs only)
○ Dual-plate wafer check valve (space-saving, high-flow applications)
9.3.1 Check valves shall be installed where shown on the contract drawings and at all pump discharges, equipment outlets, and any other locations where reverse flow could damage equipment or create a bypass condition.
9.3.2 Check valves shall be silent (spring-loaded, non-slam) type wherever possible to prevent water hammer.
9.3.3 Swing check valves shall be used only on horizontal runs and shall be oriented per the manufacturer's requirements; they shall not be installed in vertical downward flow orientation.
9.4 Pressure Relief Valves
30160
305075100125150160
Default: 125 psig
Per drawings
9.4.1 Pressure relief valves shall be provided on every closed hydronic circuit at the highest pressure point of the circuit, set to open before the system pressure exceeds the design maximum operating pressure, in accordance with IMC Chapter 12 and ASME B31.9.
9.4.2 Relief valve discharge piping shall be full-size, directed to an appropriate drain point or floor drain, and shall not be reduced in size or valved off at any time.
9.4.3 The relief valve shall never be used as a pressure control device; if a system's operating pressure is consistently approaching the relief valve set point, the expansion tank pre-charge pressure, sizing, or fill pressure is incorrect and shall be corrected.
9.5 Pressure-Reducing Valves
1280
12152025304050
Default: 20 psig
Per drawings
9.5.1 Where the building domestic water or city water supply is used for system make-up and the make-up supply pressure exceeds the hydronic system design fill pressure, a pressure-reducing valve (PRV) shall be installed on the make-up water line.
9.5.2 The PRV shall be set to maintain system static fill pressure as indicated on the drawings; setting the PRV too high results in over-pressurization and chronic relief valve discharge.
9.6 Strainers
1/16 in. perforated screen
1/32 in. perforated screen
20-mesh stainless steel wire
9.6.1 Full-bore Y-strainers shall be installed on the suction side of all pumps, on the entering-water side of all control valves in sizes 2 in. and below, and at any locations indicated on the contract drawings.
9.6.2 Strainer body shall be the same material as the connecting pipe.
9.6.3 The strainer screen shall be stainless steel with mesh size as recommended by the pump or control valve manufacturer for the pipe size and flow velocity.
9.6.4 Y-strainer blowdown valves shall be piped to a floor drain or provided with a hose bib.
10 Piping Specialties
10.1 Air Separators
○ In-line air separator with integral automatic vent
● Combination air/dirt separator (removes both air and sediment)
○ Air scoop (low-velocity chamber type, older design, acceptable for retrofit)
10.1.1 An air separator shall be installed on the outlet of each boiler or chiller and on the return main adjacent to the expansion tank connection, as indicated on the contract drawings.
10.1.2 Air separators shall be designed for the full system flow rate and shall provide a low-velocity chamber, coalescing media, or both to cause entrained air to collect and be automatically vented.
10.1.3 Air separators shall incorporate an integral automatic air vent on the top connection; the automatic vent shall be float-operated and shall close when liquid is present to prevent water discharge.
10.1.4 In glycol systems, the air vent shall be rated for the glycol solution and shall not discharge glycol to the atmosphere without collection provisions.
10.1.5 The pump shall be arranged to "pump away" from the air separator and expansion tank connection, which together define the point of no pressure change, so that the pump discharge is on the side of the air separator/expansion tank tee that sees increased pressure.
NOTE Incorrect placement of the air separator relative to the expansion tank connection results in system pressures that fluctuate with pump operation, causing nuisance relief valve discharge or air ingestion. (10.1.6)
NOTE Combination air and dirt separators are the preferred product for new construction because they remove both entrained air and suspended particulate in a single device, reducing system dirt loading on coils and control valves. (10.1.7)
10.2 Automatic Air Vents
● Coin-top float vent (standard for accessible locations)
○ Float vent with lock feature (for glycol systems, prevents inadvertent discharge)
○ Manual petcock vent (acceptable only where accessible and regularly serviced)
10.2.1 Automatic air vents shall be installed at all high points in the piping system that cannot be reached by the air separator's venting action.
10.2.2 Every high point, including those created by pipe offsets, riser tops, and coil headers that pitch upward, shall have an automatic vent sized for the pipe diameter.
10.2.3 In glycol systems, automatic vents shall be of a type that closes against liquid so glycol solution is not discharged in normal operation.
10.2.4 Where a vent location is in a finished ceiling or inaccessible space, the vent shall be piped to an accessible location with a drain cup.
10.3 Expansion Tanks
● Diaphragm type with butyl rubber diaphragm (standard)
○ Bladder type with replaceable internal bladder
1080
10121518202530
Default: 12 psig
Per drawings
2500
246810152030405080100150200300500
Default: 15 gallons
Per drawings
10.3.1 A diaphragm-type (bladder or diaphragm) expansion tank shall be provided on each closed hydronic circuit to absorb the volumetric expansion of system water as it is heated, maintaining system pressure within the design operating range.
10.3.2 Open expansion tanks and plain (non-diaphragm) air-cushion tanks shall not be used on new construction.
NOTE Diaphragm tanks eliminate continuous air-water contact that leads to oxygen corrosion and are the current industry standard for all commercial closed-loop systems. (10.3.3)
10.3.4 The expansion tank pre-charge pressure shall be set at the factory to equal the static pressure at the tank connection point with the system cold-filled, which is the fill pressure at the expansion tank location.
10.3.5 The Contractor shall verify the pre-charge pressure against the system static pressure calculation before installation and shall not install a tank with a pre-charge pressure that does not match the system design.
10.3.6 Tank pre-charge verification shall be documented in the commissioning records.
NOTE If the pre-charge pressure is set too high, water will not enter the tank during cold fill and the system will be over-pressurized when the water heats; if set too low, the tank accepts water during cold fill and has insufficient acceptance volume for the thermal expansion. (10.3.7)
NOTE Undersized expansion tanks result in chronic high-pressure relief valve discharge, one of the most common hydronic system problems in the field, almost always caused by either an undersized tank or incorrect pre-charge pressure. (10.3.9)
10.4 Flexible Pipe Connectors
● Braided stainless steel flexible hose with ends to match pipe system (standard)
○ Rubber expansion joint, spool type (where greater movement is required)
○ Grooved flexible coupling (where grooved pipe system is used throughout)
10.4.1 Flexible pipe connectors (flexible hose or expansion fittings) shall be provided at all pump suction and discharge connections and at all connections to rooftop, pad-mounted, and suspended equipment subject to vibration.
10.4.2 Flexible connectors shall be rated for the system service, operating pressure, temperature, and glycol concentration where applicable.
10.4.3 Flexible connectors used in vibration isolation service shall be installed with pipe guides within two pipe diameters of each end to prevent lateral movement that would reduce the isolator effectiveness and impose side loads on the pump flanges.
11 Hangers, Supports, and Pipe Guides
11.1 Hanger Standards
MSS SP-58 Type 1 — adjustable clevis hanger (standard for horizontal steel pipe)
MSS SP-58 Type 7 — beam clamp with clevis hanger
MSS SP-58 Type 9 — adjustable swivel split ring
MSS SP-58 Type 40 — insulated clevis hanger with insulation shield
Insulation protection saddle (pipe cradle with pre-insulated insert)
Pre-insulated pipe support assembly
11.1.1 Pipe hangers and supports shall conform to MSS SP-58, the consolidated standard for materials, design, manufacture, selection, application, and installation of pipe hangers and supports.
11.1.2 All hangers shall be new and free of defects, and the Contractor shall not reuse hangers from other projects or from demolition work.
11.1.3 Hangers shall be selected for the pipe material, size, insulation outside diameter, and operating temperature in accordance with MSS SP-58 type designations.
11.1.4 Insulated pipe shall never be supported by a hanger that compresses, punctures, or bridges the insulation.
11.1.5 Insulation shields (load-bearing inserts) shall be provided at every hanger on insulated pipe, and the shield length shall be sufficient to distribute the pipe load without compressing the insulation below the specified minimum thickness.
NOTE Thermal insulation that is compressed at support points creates cold bridges on chilled water piping (resulting in condensation drips) and thermal losses on hot water piping. (11.1.6)
11.2 Hanger Spacing — Steel Pipe
3/4 in. through 1 in. — 7 ft; 1-1/4 in. through 1-1/2 in. — 9 ft; 2 in. — 10 ft; 2-1/2 in. through 3 in. — 12 ft; 4 in. — 14 ft; 6 in. — 17 ft; 8 in. — 19 ft; 10 in. — 22 ft; 12 in. — 23 ft
Per drawings
11.2.1 Maximum hanger spacing for steel pipe shall not exceed the values in the datasheet above, measured center-to-center of supports on horizontal runs.
11.2.2 Vertical runs shall have a riser clamp at each floor penetration or at intervals not exceeding the equivalent of the horizontal spacing, whichever is less.
11.2.3 The Contractor shall add supplemental supports at equipment connections, at changes in direction, and where the distributed load from valves, flanges, or specialty items requires an intermediate support.
11.3 Hanger Spacing — Copper Tube
1/2 in. through 1 in. — 5 ft; 1-1/4 in. through 2 in. — 6 ft; 2-1/2 in. through 3 in. — 8 ft; 4 in. — 10 ft
Per drawings
11.3.1 Maximum hanger spacing for copper tube on horizontal runs shall not exceed the values in the datasheet above.
NOTE Copper tube must be supported more frequently than steel pipe of equivalent nominal size because copper is significantly less stiff; inadequate hanger spacing on copper results in sag that traps air at high points and concentrates bending stress at fittings. (11.3.2)
11.4 Pipe Anchors
○ Welded anchor assembly per structural drawings
○ Fabricated clamp-and-bracket anchor per Contractor's shop drawing, Engineer-approved
● Pre-engineered pipe anchor assembly per manufacturer's load ratings
11.4.1 Pipe anchors shall be provided at all locations shown on the contract drawings to fix the pipe position and absorb the reaction forces of expansion loops, expansion joints, and branch connections.
11.4.2 Anchors shall be designed by the Engineer of Record to resist the actual axial forces developed by thermal expansion, fluid pressure thrust, and any seismic or wind loads applicable to the system.
11.4.3 The Contractor shall not substitute anchor locations or omit anchors shown on the drawings; the entire expansion compensation design is predicated on the force path defined by the anchor-guide-loop system, and any change to anchor locations requires re-evaluation of all expansion compensation between those anchors.
11.5 Pipe Guides
First guide: 4 pipe diameters; second guide: 14 pipe diameters; subsequent: 40 pipe diameters
Per expansion device manufacturer's published guide spacing chart
11.5.1 Pipe guides shall be provided to constrain pipe movement to the axial direction only, preventing lateral buckling and side movement at expansion loops and between anchors.
11.5.2 Guides shall be close-clearance (not tight) to allow axial movement and shall not bind the pipe.
11.5.3 The first guide on each side of an expansion loop or expansion joint shall be within two pipe diameters of the expansion device; subsequent guides shall be spaced per the expansion device manufacturer's installation instructions, typically at intervals not exceeding 40 to 50 pipe diameters.
NOTE Spacing guides too far apart is one of the leading causes of lateral buckling (snaking) in piping with expansion devices, which eventually fatigues both the expansion device and adjacent joints. (11.5.4)
12 Thermal Expansion Compensation
12.1 General
NOTE The thermal expansion of carbon steel is approximately 0.0073 in./ft/100°F temperature rise. (12.1.1)
12.1.2 A 200 ft straight run of HHW piping operating at 180°F installed at 70°F will expand approximately 0.0073 × 200 × (180 − 70) ≈ 1.6 in., which must be absorbed without imposing excessive stress.
NOTE Copper has a higher coefficient of linear thermal expansion than steel (approximately 0.0095 in./ft/100°F), so copper pipe on long runs requires even more careful expansion analysis. (12.1.3)
○ Natural flexibility — direction changes designed as expansion offsets
○ Expansion loops — fabricated from straight pipe and elbows
○ Axial expansion joints (bellows type)
● Combined — natural flexibility supplemented by loops or joints where required
12.1.4 All steel hydronic piping shall be analyzed for thermal expansion and designed with adequate compensation to prevent overstress of piping, fittings, equipment connections, and supports.
12.1.5 Expansion compensation shall be provided by one or more of the following methods: natural flexibility of changes in direction (L-bends, Z-offsets), expansion loops, or expansion joints.
12.1.6 Expansion joints (bellows, ball joints, or flexible hose) shall be used only where natural flexibility and expansion loops cannot accommodate the required movement within the available space.
NOTE Natural flexibility is preferred because it requires no maintenance and cannot fail; expansion loops are the second choice. (12.1.7)
12.2 Expansion Loops
● U-loop (single-plane offset, standard)
○ L-offset (change-of-direction flexibility)
○ Z-offset (double-plane, for congested routing)
Per drawings
12.2.1 Expansion loops shall be fabricated from the same pipe and fittings as the main run, using long-radius elbows (1.5D minimum radius).
12.2.2 The loop dimensions shall be calculated to maintain piping stresses within ASME B31.9 allowables with the calculated expansion and shall be indicated on the contract drawings.
12.2.3 The Contractor shall not field-size expansion loops; sizing shall be done by the Engineer of Record or by the Contractor's licensed mechanical engineer and submitted for review.
12.2.4 Anchors at both ends of the loop run and guides between the anchor and the loop are essential; loops installed without proper anchors and guides will move laterally rather than expanding the loop, which defeats their purpose.
12.3 Expansion Joints
● Axial bellows — single-plane axial movement only
○ Hinged — angular rotation, installed in pairs for lateral offset
○ Gimbal — multi-plane angular rotation
○ Rubber expansion joint — vibration isolation and small movement
Per drawings
12.3.1 Expansion joints (axial bellows, gimbal, or universal joints) shall be used only where shown on the contract drawings.
12.3.2 The Contractor shall install expansion joints in strict accordance with the manufacturer's installation instructions, including the correct pre-compression or pre-extension adjustment and the required number and location of anchors and guides.
12.3.3 Bellows-type expansion joints installed without control rods on a straight run between anchors shall be positively guided to prevent pressure-thrust buckling.
12.3.4 Expansion joints shall not be installed in buried locations unless specifically designed and rated for buried service.
13 Pipe Insulation
13.1 General Insulation Requirements
○ ANSI/ASHRAE/IES 90.1, current adopted edition
○ International Energy Conservation Code (IECC), current adopted edition
● More stringent of 90.1 and local energy code (default)
13.1.1 All hydronic piping shall be insulated to the thicknesses required by ANSI/ASHRAE/IES 90.1 for the applicable fluid temperature and pipe size.
13.1.2 Where the local energy code adopts a different standard, the more stringent of 90.1 and the local energy code shall apply.
13.1.3 Insulation shall be applied after pressure testing is complete and the pipe surface is clean, dry, and free of rust and scale.
NOTE Pipe insulation applied over damp or corroded pipe is a common quality deficiency that accelerates pipe corrosion and degrades insulation performance. (13.1.4)
13.2 Heating Hot Water Insulation
● Fiberglass (glass fiber) pipe insulation, ASTM C553 or C1290, with ASJ facing
○ Mineral wool (rock wool) pipe insulation with vapor-barrier jacket
○ Pre-insulated pipe assembly (for underground or tunneled distribution)
1.0
1.5
2.0
Per ASHRAE 90.1 Table 6.8.3-1
1.5
2.0
2.5
Per ASHRAE 90.1 Table 6.8.3-1
13.2.1 Insulation for HHW supply and return piping shall be fiberglass pipe insulation with an all-service jacket (ASJ) facing conforming to ASTM C553 or ASTM C1290.
13.2.2 The HHW insulation shall be rated for the maximum system operating temperature.
13.2.3 Minimum HHW insulation thickness shall comply with ASHRAE 90.1 Table 6.8.3-1 for heating hot water service at the design supply temperature.
13.3 Chilled Water Insulation
● Flexible closed-cell elastomeric, ASTM C534 (preferred — inherent vapor barrier)
○ Fiberglass pipe insulation with factory vapor-barrier jacket
0.75
1.0
1.5
Per ASHRAE 90.1 Table 6.8.3-2
1.0
1.5
2.0
Per ASHRAE 90.1 Table 6.8.3-2
13.3.1 Insulation for CHW supply and return piping shall be flexible closed-cell elastomeric cellular insulation conforming to ASTM C534, or fiberglass pipe insulation with a factory-applied vapor barrier jacket.
13.3.2 The insulation system for CHW piping shall provide an effective vapor retarder to prevent condensation on the cold pipe surface.
13.3.3 The vapor retarder shall be continuous, including at fittings, valves, and flanges, which shall be insulated with mitered sections, blanket insulation, or pre-molded fitting covers with a vapor-barrier seam.
13.3.4 Elastomeric foam insulation shall not be used on HHW piping above its rated temperature.
13.3.5 Adhesive closures on elastomeric insulation shall be the manufacturer's specified adhesive applied to both surfaces before joining; mechanical staples and tape alone are not acceptable for sealing the longitudinal seam.
NOTE Any breach in the CHW vapor retarder allows moisture to diffuse into the insulation and reach the cold pipe, where it condenses and promotes external corrosion. (13.3.6)
NOTE Elastomeric foam insulation is preferred for CHW piping because the closed-cell structure provides a built-in vapor retarder and the flexible material is easily applied around fittings and valves without complex mitered sections, but it has a lower service temperature limit than fiberglass. (13.3.7)
13.4 Condenser Water Insulation
○ Yes — insulate per drawings (spaces where pipe sweating is a concern)
● No — condenser water piping uninsulated (standard for fully indoor routing)
13.4.1 Where condenser water piping passes through spaces where surface temperatures could cause discomfort, sweating, or where energy conservation analysis indicates a benefit, insulation shall be applied as indicated on the contract drawings.
NOTE Condenser water piping serving cooling towers is open-circuit, and insulation is typically not required for energy conservation or condensation prevention on condenser water systems. (13.4.2)
13.5 Insulation Application and Accessories
● All-service jacket (ASJ) — white kraft paper/foil laminate with self-sealing lap
○ PVC jacketed (for exposed/mechanical room locations)
○ Canvas jacket with lagging adhesive (for decorative or museum applications)
● PVC jacket over existing insulation
○ Aluminum jacket (for outdoor or high-traffic mechanical room piping)
○ ASJ facing with no additional jacket (acceptable in clean mechanical rooms)
13.5.1 Pipe insulation shall be applied in full-length sections with longitudinal seams on the side of the pipe, not on the top or bottom, to minimize the effect of any seam opening on the vapor barrier.
13.5.2 Sections shall be staggered so that circumferential joints do not align on adjacent layers where double-layer insulation is specified.
13.5.3 All joints, seams, and the overlap at fittings shall be sealed with the insulation manufacturer's specified adhesive; vapor-retarder tape may be used for the outer jacket seam on CHW insulation but shall not be the only sealing method on the vapor barrier.
14 Installation
14.1 General Installation Requirements
14.1.1 Piping shall be installed in accordance with ASME B31.9, the contract drawings, the approved coordination drawings, and the requirements of this standard.
14.1.2 The Contractor shall thoroughly examine all piping materials upon delivery and shall reject any pipe, fitting, valve, or specialty item that is dented, kinked, cracked, improperly threaded, or otherwise defective.
14.1.3 Defective material shall be removed from the site immediately and replaced.
14.1.4 Pipe shall be installed so that it is plumb, level, and aligned with the adjacent piping, structural grid, and building geometry.
14.1.5 All horizontal supply and return mains shall pitch a minimum of 1/8 in. per foot toward the low point designated for drain connections.
14.1.6 Where the system geometry does not permit continuous pitch, local low points shall be provided with drain valves and local high points shall be provided with automatic air vents.
NOTE Racking, sagging, and misaligned pipe is visually unacceptable and causes uneven stress distribution at joints and supports. (14.1.7)
14.2 Pipe Penetrations
14.2.1 Where piping passes through walls, floors, and ceilings, sleeves shall be provided that are two pipe sizes larger than the outside diameter of the insulated pipe.
14.2.2 Sleeves shall be set flush with the finished wall surface on each side.
14.2.3 Pipe shall be centered in the sleeve, and the annular space shall be packed with a listed firestopping material where the penetration is through a fire-rated assembly, in accordance with the IBC and the contract drawings.
14.2.4 Pipe shall not bear on the sleeve; the sleeve is a clearance sleeve, not a support, and the pipe shall be independently supported on each side of the penetration.
14.2.5 Escutcheon plates shall be provided at all exposed penetrations through finished surfaces.
14.3 Drains and Drain Valves
14.3.1 Drain valves shall be provided at all low points in the piping system, at the base of all risers, at all equipment isolation valve pairs, and at any other location where the system cannot be drained without disassembly.
14.3.2 Drain valves shall be ball-type with hose bib end connection, minimum 3/4 in. size.
14.3.3 Plugged nipples are not acceptable as drain provisions; all drain points shall have a valve.
NOTE Ball-type drain valves are preferred over hose bibs for system drain service because they provide positive full-bore shutoff. (14.3.4)
14.4 Equipment Connections
14.4.1 Piping connections to all equipment — chillers, boilers, heat exchangers, coils, pumps, and cooling towers — shall include isolation valves on both supply and return, a drain valve between the isolation valves on each side, and a union or flanged connection to allow equipment removal without disturbing the distribution piping.
14.4.2 All equipment connections shall be flexible connector, union, or flanged to allow equipment service without cutting piping.
14.4.3 Grouted-in or welded equipment connections that prevent removal of the equipment without cutting pipe are not acceptable.
14.5 Valve Accessibility
14.5.1 All isolation valves, balancing valves, check valves, pressure relief valves, pressure-reducing valves, and automatic air vents shall be located so they are accessible for operation and maintenance without the need for cutting finishes, removing permanent construction, or using unusual tools.
14.5.2 Where system layout results in valves above a hard ceiling, access panels shall be provided at every such valve location.
14.5.3 The Contractor shall coordinate access panel locations with the ceiling Contractor and shall identify all above-ceiling valve locations on the record drawings.
14.6 Labeling and Identification
● ASME A13.1 — yellow label with black text (dangerous contents)
○ Green label with white text (per ANSI/ASME A13.1 optional scheme)
Per drawings
● ASME A13.1 — green label with white text (safe/low hazard)
○ Blue label (common industry practice for CHW)
Per drawings
14.6.1 All supply and return piping shall be labeled with the system name (HHW, CHW, CW), flow direction, and pipe size at intervals not exceeding 25 ft on each straight run, at each side of every wall, floor, and ceiling penetration, and adjacent to every valve.
14.6.2 Labels shall be color-coded per ASME A13.1 or per the Owner's building-wide color-coding standard if one is established.
14.6.3 Valve tags shall be brass or aluminum, permanently engraved or stamped with the valve number per the valve schedule.
14.6.4 Cable ties or wire shall be used to attach valve tags; adhesive tags are not acceptable because they fall off in mechanical rooms.
15 Cleaning, Flushing, and Chemical Treatment
15.1 Sequence Overview
15.1.1 System cleaning, flushing, and initial chemical treatment shall be completed in the following sequence before pressure testing is witnessed by the Engineer: (1) pre-flush mechanical cleaning to remove gross construction debris; (2) high-velocity dynamic flushing to remove fine debris, scale, and pipe compound; (3) water sample collection and evaluation; (4) drain and rinse; (5) initial fill with treated water and chemical inhibitor; and (6) baseline chemistry analysis.
15.1.2 Where the contract documents require witnessing of the pressure test before insulation, flushing shall be completed before the witnessed test, and insulation shall not begin until after the test is completed and documented.
NOTE Pressure testing on cleaned, chemically treated water is performed after flushing is complete so that the test water matches the operating chemistry and does not introduce contamination. (15.1.3)
15.2 Pre-Flush Cleaning
● Full-bore bypass valves across each terminal unit coil (required)
○ Modular flushing cart with temporary connections at equipment headers
Per drawings — flushing plan
15.2.1 Before flushing, the Contractor shall remove and clean or replace all Y-strainer screens, shall verify that all control valves and automatic control devices are protected or bypassed, and shall install temporary bypasses across all coils and terminal unit heat exchangers so that the full flush velocity is achieved in the mains.
15.2.2 Temporary bypasses shall be full-bore and shall be clearly tagged for removal before system commissioning.
NOTE Equipment manufacturers' coil and heat exchanger passages are too small to flush at the required velocity; flushing through coils at inadequate velocity leaves debris in the equipment and can pack fine debris into the coil fins and core passages where it is difficult to remove. (15.2.3)
15.3 Flushing Velocity
2.55
2.533.545
Default: 3 ft/s
15.3.1 Flushing shall be performed with clean potable water at a flow velocity of not less than 3 ft/s (0.9 m/s) in every section of main and branch piping.
15.3.2 The Contractor shall calculate the flow rate required to achieve 3 ft/s in each pipe segment and shall use portable pumping equipment capable of delivering that flow rate.
15.3.3 The flushing plan shall demonstrate that 3 ft/s is achieved in every segment, including the largest mains.
NOTE The minimum flush velocity is the most critical parameter; at lower velocities, particulate is not fully suspended and is not carried out of the system, and flushing through the building's permanent circulation pumps at normal system flow rates is generally not sufficient in large-diameter distribution mains. (15.3.4)
15.4 Flushing Duration and Acceptance
○ Visual clarity — discharge water matches clarity of city water supply
● Turbidity ≤ 5 NTU on two consecutive 30-minute samples
○ Per laboratory analysis protocol specified by water treatment consultant
15.4.1 Flushing shall continue until the discharge water is visually clear.
15.4.2 Samples shall be collected from the flush discharge every 30 minutes after initial clarity is achieved and evaluated for turbidity and particulate.
15.4.3 Flushing shall be deemed complete when two consecutive 30-minute samples both show turbidity below 5 NTU (Nephelometric Turbidity Units) or visual clarity equivalent to clear tap water, whichever criterion is used per the accepted flushing plan.
15.4.4 Flushing reports shall document the start time, end time, total volume flushed, and the turbidity readings.
15.5 System Fill Water Quality
15.5.1 After flushing and draining, the system shall be filled with water meeting the requirements of the water treatment program specified in Hvac Water Treatment. 15.5.2 Fill water shall be either potable city water or treated water with hardness, pH, and dissolved oxygen as specified by the water treatment consultant.
15.5.3 Systems that will be operated with a glycol solution shall be filled with the glycol pre-mix or by adding inhibited glycol concentrate to the fill water connection during fill, in accordance with the glycol supplier's instructions.
15.6 Initial Chemical Treatment
○ Molybdate-based inhibitor (HHW and CHW, no aluminum components)
○ Nitrite-based inhibitor (HHW only, compatible with steel and iron)
○ Phosphate-based inhibitor (CHW systems with mixed metallurgy)
● Per water treatment consultant's specification
7.59.5
7.588.599.5
Default: 8.5 (unitless pH)
15.6.1 After system fill, an initial charge of corrosion inhibitor, scale inhibitor, and, if applicable, biocide shall be added in the concentrations recommended by the water treatment consultant for the initial passivation of the system.
15.6.2 The Contractor shall circulate the treated water for a minimum of 72 hours before collecting the baseline water chemistry sample.
15.6.3 Baseline chemistry results shall be submitted to both the Engineer of Record and the Owner's water treatment service provider to establish the starting reference for the ongoing chemical treatment program.
15.6.4 The actual baseline pH target shall be confirmed by the water treatment consultant for the specific system metallurgy and inhibitor program selected.
NOTE A pH of 8.5 provides a mildly alkaline environment that passivates carbon steel surfaces and minimizes corrosion rates while being compatible with copper tube and brass fittings; pH below 7.5 is corrosive to steel and pH above 9.5 attacks copper. (15.6.5)
15.7 Strainer Screen Cleaning After Initial Operation
15.7.1 Y-strainer screens and dirt separator bowls shall be removed and cleaned after the first 24 hours and again after the first 72 hours of system operation after commissioning.
15.7.2 The initial strainer-cleaning protocol shall be documented in the O&M manual.
NOTE Strainer screens not cleaned during this initial period will blind and cause pump cavitation or inadequate flow to terminal units, generating service calls and potentially damaging control valves or coil circuits, because initial operation invariably dislodges scale, weld spatter, brazing flux residue, and other debris that was not captured during flushing. (15.7.3)
16 Pressure Testing
16.1 General
16.1.1 All hydronic piping shall be pressure tested before insulation is applied and before connection to equipment that is not rated for the test pressure.
16.1.2 The test shall demonstrate that all joints, welds, brazes, and fittings are leak-free and that the as-installed system can withstand the test pressure without permanent deformation or distress.
16.2 Hydrostatic Test
100250
100125150175200225250
Default: 150 psig
Per drawings
16.2.1 Hydronic piping shall be subjected to a hydrostatic test pressure of not less than 1.5 times the design maximum operating pressure, but not less than 100 psig, in accordance with ASME B31.9 and IMC Chapter 12.
16.2.2 Where the calculated 1.5× value exceeds the pressure rating of any installed component (expansion tank, equipment, pressure relief valve set point), the test boundary shall be established to exclude that component and it shall be separately pressure tested at its rated pressure.
16.2.3 The test medium shall be clean potable water.
16.2.4 Air or nitrogen shall not be used as the primary test medium for hydronic piping, because the elastic energy stored in a compressed gas creates an explosion hazard if a joint fails during the test.
16.2.5 The test pressure shall be applied using a hand pump or small power pump and gauged at the test point.
NOTE The hydrostatic (water pressure) test is the standard test method for hydronic piping; water is incompressible and a test joint failure releases water rather than explosive energy. (16.2.6)
16.3 Test Procedure
1 hour
2 hours
4 hours
8 hours
16.3.1 The Contractor shall fill the system from the lowest point, venting air from all high points as the system fills, until all air is expelled and the system is full of water.
16.3.2 The test pressure shall then be applied and held for a minimum of two hours.
16.3.3 During the test, the Contractor and the Engineer's inspector shall walk all accessible piping and visually inspect every joint, fitting, weld, braze, and valve body for leaks, wet marks, seepage, or sweating.
16.3.4 No visible leaks of any magnitude shall be acceptable; a leak at any joint requires the test to be stopped, the joint repaired, the system refilled, and the test repeated from the beginning.
16.4 Pressure Gauge Requirements
0-160 psig (for tests up to 100 psig)
0-200 psig (for tests up to 150 psig)
0-300 psig (for tests up to 200 psig)
Calibrated instrument with range approximately 1.5-2× test pressure
16.4.1 Test pressure gauges shall be calibrated, with a range of approximately 1.5 to 2 times the test pressure, and shall have graduations that allow pressure changes of 5 psi or less to be read.
16.4.2 Uncalibrated or unranged gauges shall not be used for acceptance testing.
16.4.3 The pressure gauge shall be located at the low point of the test boundary for hydrostatic tests; readings at the pump or at a high point do not represent the maximum pressure in the system and shall not be used as the sole gauge for test acceptance.
16.5 Pneumatic Test (Alternative)
● Hydrostatic (water) — standard and required unless Engineer approves otherwise
○ Pneumatic (clean dry nitrogen) — alternative with Engineer's written approval only
16.5.1 Where it is not practicable to perform a hydrostatic test — for example, on pre-insulated piping systems that cannot be wet-tested before insulation is applied, or on systems in completed spaces where water damage from a joint failure would be catastrophic — a pneumatic test using clean dry nitrogen is acceptable, subject to the approval of the Engineer of Record.
16.5.2 Pneumatic tests shall be conducted at a maximum pressure not exceeding the smaller of 150% of design pressure or the lowest pressure rating of any component in the test boundary.
16.5.3 A pneumatic test shall use a preliminary air test at 25 psig to check for gross leaks by sound before proceeding to full test pressure.
16.5.4 Personnel and equipment not essential to the test shall be excluded from the immediate area during pressurization.
16.6 Test Documentation
16.6.1 A signed and dated pressure test report shall be prepared for each test, including the date of test; the test boundaries (pipe systems and locations included); the test medium; the test pressure; the test duration; the name and signature of the Contractor's representative performing the test; and the name and signature of the Engineer's inspector witnessing the test.
16.6.2 The report shall record "pass" only if no pressure drop was observed during the hold period and no leaks were found by visual inspection.
16.6.3 A "pass with repairs" notation is not acceptable; each repaired joint requires a new complete test record.
17 Commissioning and Balancing
17.1 System Commissioning
17.1.1 After pressure testing, initial flushing, chemical treatment, and insulation, the hydronic systems shall be commissioned in accordance with the commissioning plan.
17.1.2 Commissioning shall include start-up of all pumps, verification of flow direction in every circuit, calibration of differential pressure sensors, verification of expansion tank pre-charge, verification of pressure relief valve set points, and verification that all automatic air vents and air separators are functioning.
17.1.3 All deficiencies identified during commissioning shall be corrected before the TAB contractor is called to balance the system.
17.2 Testing, Adjusting, and Balancing (TAB)
17.2.1 The TAB contractor shall balance each hydronic system so that design flow is achieved at each terminal unit within ±10% of the design flow rate shown on the contract drawings, using the calibrated circuit setter balancing valves installed by the Contractor.
17.2.2 The Contractor shall provide the TAB contractor with the valve schedule identifying each valve number and design flow rate.
17.2.3 Any circuit that cannot be balanced within tolerance because the installed pipe size is smaller than design, a strainer is blocked, or a valve is defective shall be immediately reported to the Engineer of Record, and the Contractor shall correct the physical deficiency.
17.2.4 TAB reports shall include each valve identification, design flow, measured flow, and percent of design for every terminal unit and branch.
17.2.5 Hydronic TAB shall be coordinated with the air-side TAB required by Testing Adjusting And Balancing so that both air and water sides of each coil are balanced in the same commissioning sequence. 18 Warranty
18.1 Contractor Warranty
1 year from substantial completion
2 years from substantial completion
Per contract General Conditions
18.1.1 The Contractor shall warrant all hydronic piping work — including materials, joints, welds, brazes, valve packings, insulation, and chemical treatment services — against defects in workmanship and materials for a period of not less than one year from the date of substantial completion, or the project warranty period specified in the General Conditions, whichever is longer.
18.1.2 Any leak, deterioration of insulation, valve packing failure, or corrosion attributable to improper installation discovered during the warranty period shall be repaired by the Contractor at no additional cost to the Owner.
18.2 Equipment Warranties
1 year
2 years
5 years (diaphragm/bladder type — typical for listed expansion tanks)
18.2.1 Specialty items — expansion tanks, air separators, balancing valves, pressure relief valves, pressure-reducing valves, and flexible connectors — shall carry the manufacturer's standard warranty against defects in materials and workmanship.
18.2.2 The Contractor shall record and transmit to the Owner the start date, end date, and warranty terms for each warranted item.
18.2.3 The warranty period for any item that requires service during the project warranty period shall be documented; warranty periods do not toll for items that are repaired or replaced during the original warranty term unless the manufacturer provides a new warranty on the replacement.
18.3 Common Deficiencies and RFI Generators
NOTE The following conditions are the most frequent sources of field RFIs, warranty calls, and commissioning failures on hydronic piping projects. (18.3.1)
18.3.2 The Contractor shall specifically review each common deficiency item before final inspection.
18.3.3 The expansion tank pre-charge shall be field-verified against the static fill pressure before tank installation, because incorrect pre-charge pressure is the leading cause of chronic pressure relief valve discharge and system pressure instability.
18.3.4 Every true high point, including those created by pipe offsets, shall have an air vent, because automatic air vents installed at anything other than the true high point in the piping will not vent.
18.3.5 The initial strainer-cleaning protocol shall be included in the O&M documentation and performed as specified, because strainer screens that are not cleaned after the initial system operation quickly block flow, causing poor performance and pump trips.
18.3.6 Every expansion loop installation shall be visually verified against the guide and anchor plan before insulation, because loops installed without proper anchors and guides allow the pipe to snake sideways instead of expanding within the loop, eventually fatiguing the loop elbows.
18.3.7 All balancing valves shall be on the return piping of each terminal unit, because balancing valves installed on the supply side rather than the return side cannot be balanced accurately.
18.3.8 Every CHW fitting, flange, and valve shall be insulated with fitting covers or mitered sections sealed with manufacturer's vapor-retarder adhesive before final inspection, because chilled water insulation vapor retarder breaches at supports, valve bodies, and fitting insulation seams cause condensation drips on ceilings and floors.