+---
+title: General-Duty Valves for HVAC Piping
+category: Mechanical / Piping & Pumps
+toc_depth: 3
+description: >
+ When to use: General-duty, non-control isolation, shutoff, and non-modulating
+ throttling valves in HVAC piping — hot-water heating, chilled water,
+ condenser water, steam and condensate, and dual-temperature hydronic circuits in
+ commercial, institutional, and industrial buildings. Covers gate, globe, ball,
+ butterfly, check, and plug valves, NPS 1/4 through NPS 12 and larger, in bronze,
+ brass, cast iron, ductile iron, and steel, Class 125 through Class 300.
+ Not intended for: modulating automatic control valves, balancing valves, circuit
+ setters, triple-duty valves, pressure-independent control valves, and backflow
+ preventers (see [[sync/hydronic-specialties]]); refrigerant isolation and service
+ valves (see [[sync/refrigerant-piping]]); plumbing piping valves for domestic
+ water, sanitary, storm, and gas (see [[sync/plumbing-piping-valves]]); pump-package
+ accessory valves furnished with the pump (interface per [[sync/hvac-pumps]]);
+ hangers and support hardware for valve assemblies (see [[sync/hangers-and-supports]]);
+ and high-pressure or high-temperature industrial process valves rated above
+ Class 600 or above 366 °C.
+---
+
+# Scope {toc}
+
+## This Standard covers general-duty valves furnished and installed in HVAC piping systems for isolation, shutoff, and non-modulating throttling service. {note}
+
+## General-duty valves are the manually operated isolation and throttling valves that punctuate every hydronic and steam distribution system: the gate valve at the base of a riser, the ball valve on a coil branch, the butterfly valve isolating a chiller, the swing check at a pump discharge. They are deliberately distinct from the automatic, actuated control valves that modulate flow to maintain a setpoint. A general-duty valve is either open or closed (isolation duty) or set once and left (coarse throttling duty); it is never expected to regulate flow continuously against a control signal. {note}
+
+## The systems addressed are hot-water heating, chilled water, condenser water, steam and steam condensate, and dual-temperature hydronic circuits. {note}
+
+### Valves shall be provided for isolation of every piece of HVAC equipment, every branch takeoff, every riser, and every section of main that must be drained, serviced, or removed independently.
+
+### Valves furnished under this Standard shall be limited to manual operation: handwheel, lever, gear operator, or chainwheel.
+
+### Automatic and powered actuation for flow control is excluded from this Standard; modulating control valves shall be furnished under [[sync/hydronic-specialties]].
+
+## Boundaries with adjacent Standards. {note}
+
+## The following items are deliberately outside this Standard so that no device is specified twice and no service condition falls through a seam between Standards: {note}
+
+- Modulating control valves, automatic balancing valves, circuit setters, triple-duty valves, pressure-independent control valves, and backflow preventers are hydronic specialty devices — see [[sync/hydronic-specialties]].
+- Refrigerant isolation valves and refrigerant service valves on DX and chiller circuits are covered by [[sync/refrigerant-piping]].
+- Domestic water, sanitary, storm, and fuel-gas piping valves are plumbing devices — see [[sync/plumbing-piping-valves]].
+- Pump suction and discharge isolation valves furnished as part of a pump package are specified with the pump; coordinate the interface per [[sync/hvac-pumps]].
+- Pipe valves are supported by hangers and supports furnished under [[sync/hangers-and-supports]], not by the piping connections.
+- The piping into which these valves are installed is specified under [[sync/hydronic-piping]].
+
+## Service-condition limit. {note}
+
+### Valves under this Standard shall be applied only within HVAC service conditions: working pressures through Class 300 and service temperatures at or below 366 °C.
+
+### Process valves rated above Class 600, or required above 366 °C, are outside this Standard and shall be specified under the applicable process piping Standard.
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| MSS SP-25 | Standard Marking System for Valves, Fittings, Flanges and Unions |
+| MSS SP-61 | Pressure Testing of Valves |
+| MSS SP-67 | Butterfly Valves |
+| MSS SP-70 | Cast Iron Gate Valves, Flanged and Threaded Ends |
+| MSS SP-71 | Cast Iron Swing Check Valves, Flanged and Threaded Ends |
+| MSS SP-80 | Bronze Gate, Globe, Angle, and Check Valves |
+| MSS SP-85 | Cast Iron Globe and Angle Valves, Flanged and Threaded Ends |
+| MSS SP-110 | Ball Valves Threaded, Socket-Welding, Solder Joint, Grooved and Flared Ends |
+| ASME B16.34 | Valves — Flanged, Threaded, and Welding End |
+| ASME B16.10 | Face-to-Face and End-to-End Dimensions of Valves |
+| ASME B16.18 | Cast Copper Alloy Solder Joint Pressure Fittings |
+| ASME B16.1 | Gray Iron Pipe Flanges and Flanged Fittings (Classes 25, 125, and 250) |
+| ASME B16.5 | Pipe Flanges and Flanged Fittings (NPS 1/2 through NPS 24) |
+| ANSI/FCI 70-2 | Control Valve Seat Leakage |
+| ASHRAE 90.1 | Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings |
+
+# Submittals {toc}
+
+## Action Submittals. {note}
+
+### The Contractor shall submit the following action submittals for review before any valve is procured:
+
+- Product data for each valve type, size, and pressure class, including pressure-temperature rating tables, body and trim materials, end-connection type, and operator type.
+- A valve schedule cross-referencing each valve mark on the drawings to its type, size, class, service, and location.
+- Manufacturer cut sheets marked to show the specific model proposed for each service, with non-applicable options struck through.
+- Certified face-to-face and end-to-end dimensions for flanged and grooved valves where space is constrained.
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - Product data per valve type and class
+ - Valve schedule keyed to drawing marks
+ - Marked cut sheets identifying proposed models
+ - Certified face-to-face / end-to-end dimensions
+default:
+ - Product data per valve type and class
+ - Valve schedule keyed to drawing marks
+ - Marked cut sheets identifying proposed models
+```
+
+## Informational Submittals. {note}
+
+### The Contractor shall submit the following informational submittals:
+
+- Factory hydrostatic shell-test and seat-test certificates, or a statement of compliance with MSS SP-61, for the valve types furnished.
+- Material certifications (mill or foundry) for body, bonnet, disc, stem, and seat where required by the Engineer of Record.
+- Manufacturer installation instructions, including orientation limits and torque values for grooved and flanged joints.
+
+```datasheet
+label: Informational Submittals Required
+type: checkbox
+options:
+ - Factory hydrostatic / seat-test certificates (MSS SP-61)
+ - Material certifications for body and trim
+ - Manufacturer installation instructions
+default:
+ - Factory hydrostatic / seat-test certificates (MSS SP-61)
+ - Manufacturer installation instructions
+```
+
+## Closeout Submittals. {note}
+
+### The Contractor shall submit the following closeout submittals before substantial completion:
+
+- A final, as-built valve schedule reconciling installed valve tags to the owner's P&ID and valve-numbering system.
+- Operation and maintenance data, including repacking and seat-renewal procedures for repairable valve types.
+- Warranty documentation for each valve manufacturer.
+
+```datasheet
+label: Closeout Submittals Required
+type: checkbox
+options:
+ - As-built valve schedule keyed to owner P&ID
+ - O&M data (repacking, seat renewal)
+ - Manufacturer warranty documentation
+default:
+ - As-built valve schedule keyed to owner P&ID
+ - O&M data (repacking, seat renewal)
+ - Manufacturer warranty documentation
+```
+
+# Quality Assurance {toc}
+
+## Source quality. {note}
+
+### Each valve type, size, and class shall be the product of a single manufacturer to the extent practicable, so that pressure-temperature ratings, trim materials, and spare parts remain consistent across the project.
+
+### Valves shall be manufactured under a quality system conforming to ISO 9001 or an equivalent recognized program.
+
+### Valves shall bear the manufacturer's identification, pressure class, and body material cast or stamped on the body in accordance with MSS SP-25.
+
+## Standards compliance by valve type. {note}
+
+## Each valve family is governed by a specific MSS or ASME standard; specifying to the wrong standard invites a valve that is dimensionally or metallurgically inappropriate for the service. {note}
+
+### Bronze gate, globe, angle, and check valves shall conform to MSS SP-80.
+
+### Iron and ductile-iron butterfly valves shall conform to MSS SP-67.
+
+### Brass and bronze ball valves shall conform to MSS SP-110.
+
+### Cast-iron gate valves shall conform to MSS SP-70.
+
+### Cast-iron swing check valves shall conform to MSS SP-71.
+
+### Cast-iron globe and angle valves shall conform to MSS SP-85.
+
+### Steel, alloy-steel, and stainless-steel valves shall conform to ASME B16.34.
+
+### Flanged-valve face-to-face and end-to-end dimensions shall conform to ASME B16.10 so that valves of equal size and class are interchangeable.
+
+## Regulatory basis. {note}
+
+### Shutoff valves shall be provided on each HVAC equipment connection and on each branch circuit in accordance with ASHRAE 90.1 Section 6.4.
+
+### Valve bodies in insulated piping systems shall be insulated in accordance with the insulation thickness requirements of ASHRAE 90.1 Section 6, by removable covers or field-applied insulation; valve bodies shall not be left bare.
+
+# Environmental and Service Conditions {toc}
+
+## Design conditions govern valve selection. {note}
+
+## Every valve must be rated for the worst-case combination of pressure and temperature it will see in service — and on a hydronic system that worst case is not the pump head alone. It is the static head of the building column plus pump shutoff head plus any expansion-tank fill pressure, all evaluated at the system design temperature. The single most common field failure in this Standard's scope is a Class 125 cast-iron body specified against a system whose combined static-plus-pump pressure exceeds the 200 psig cold-water rating with no margin. {note}
+
+### The Contractor shall verify, for each valve location, that the valve pressure class equals or exceeds the maximum system working pressure at the design temperature, including static head, pump shutoff head, and fill pressure.
+
+### Where the calculated maximum system working pressure exceeds 175 psig, Class 125 bodies shall not be used; Class 150 ductile-iron, Class 250 cast-iron, or Class 300 steel valves shall be specified as appropriate to the service.
+
+## Pressure-class ratings used in this Standard. {note}
+
+## The pressure classes below are the working envelopes used throughout this Standard. Steam ratings are saturated-steam ratings; cold-water (CWP / WOG) ratings apply at or below 65 °C unless the manufacturer's pressure-temperature table permits otherwise. {note}
+
+| Body / Class | Saturated steam | Cold water (CWP/WOG) | Typical HVAC use |
+|--------------|-----------------|----------------------|------------------|
+| Bronze Class 125 | 125 psig | 200 psig | Branch isolation NPS 1/4–2 |
+| Bronze Class 150 | 150 psig | 300 psig | Branch isolation, low-pressure steam NPS 1/4–2 |
+| Cast iron Class 125 | 125 psig | 200 psig | Mains NPS 2-1/2–12, ≤175 psig systems |
+| Cast iron Class 250 | 250 psig | 500 psig | Medium-pressure steam, high-rise mains |
+| Steel Class 150 | per ASME B16.34 | per ASME B16.34 | Steam mains 15–125 psig, flanged |
+| Steel Class 300 | per ASME B16.34 | per ASME B16.34 | Steam >125 psig, >175 psig hydronic |
+
+```datasheet
+label: Maximum System Working Pressure at Valve
+type: range
+unit: psig
+min: 50
+max: 400
+step: 25
+default: 150
+```
+
+```datasheet
+label: System Design Temperature
+type: range
+unit: °C
+min: 4
+max: 200
+step: 2
+default: 92
+```
+
+## Fluid and seat compatibility. {note}
+
+## Elastomer seat material must match the fluid. EPDM is the default for clean hot and chilled water and low-concentration glycol, but it swells and degrades in any petroleum-based fluid. Systems carrying oily steam condensate, or hydronic loops with glycol concentrations above roughly 50 percent or any oil contamination, require nitrile (BUNA-N) seats instead. {note}
+
+### Butterfly and resilient-seated valves in clean hot-water, chilled-water, and condenser-water service shall use EPDM seats.
+
+### Valves in oily condensate service, or in glycol systems above 50 percent concentration or with oil contamination, shall use nitrile (BUNA-N) seats; EPDM shall not be used in these services.
+
+```datasheet
+label: Resilient Seat Material
+type: radio
+options:
+ - EPDM (clean water, low glycol)
+ - Nitrile / BUNA-N (oily condensate, high glycol)
+default: EPDM (clean water, low glycol)
+```
+
+# Valve Types and Service Selection {toc}
+
+## Match the valve type to its duty. {note}
+
+## Each valve type exists because it does one job well. Choosing by familiarity rather than duty is the root of most valve RFIs: a globe valve used for simple isolation wastes pump head forever; a gate valve used for throttling erodes its seat; a wafer butterfly valve used as a dead-end isolation valve cannot be made to seal once the downstream flange is removed. The selection rules below assign each duty to its appropriate type. {note}
+
+### Gate valves shall be used for full-bore isolation in infrequently operated locations where low pressure drop in the open position is required.
+
+### Globe valves shall be used where manual throttling or frequent operation is required and the associated pressure drop is acceptable.
+
+### Ball valves shall be used for isolation, and may be used for coarse throttling, in sizes NPS 1/4 through NPS 3.
+
+### Butterfly valves shall be used for isolation, and may be used for non-precision throttling, in sizes NPS 2-1/2 and larger.
+
+### Swing check or wafer check valves shall be used for backflow prevention, typically at pump discharge.
+
+## Default selections by service. {note}
+
+## The defaults below represent the 80 percent case across commercial and institutional HVAC. They are starting points, not mandates: the Engineer of Record may select otherwise where the service warrants. {note}
+
+### For hydronic branch isolation NPS 1/2 through NPS 2, the default valve is a bronze full-port ball valve, Class 150, with threaded or solder-joint ends and a lever handle.
+
+### For chilled-water and condenser-water isolation NPS 2-1/2 and larger, the default valve is a ductile-iron lug- or wafer-body butterfly valve with an EPDM seat, Class 125, with a gear operator at NPS 6 and larger.
+
+### For pump-discharge backflow prevention, the default valve is a swing check valve matched to the pump connection size and the system pressure class.
+
+```datasheet
+label: Primary Isolation Valve Type (this service)
+type: radio
+options:
+ - Ball valve (NPS 1/4–3 isolation/throttle)
+ - Gate valve (full-bore isolation)
+ - Globe valve (throttling / frequent operation)
+ - Butterfly valve (NPS 2-1/2+ isolation)
+default: Ball valve (NPS 1/4–3 isolation/throttle)
+```
+
+```datasheet
+label: Valve Size (NPS)
+type: select
+unit: NPS
+options:
+ - "1/2"
+ - "3/4"
+ - "1"
+ - "1-1/4"
+ - "1-1/2"
+ - "2"
+ - "2-1/2"
+ - "3"
+ - "4"
+ - "6"
+ - "8"
+ - "10"
+ - "12"
+default: "2"
+drawing_ref: true
+```
+
+# Body Materials and End Connections {toc}
+
+## Body material follows size and service. {note}
+
+## Below NPS 2-1/2, bronze and brass bodies dominate hydronic and low-pressure steam service: they are economical, corrosion-resistant, and available in threaded and solder-joint ends. At NPS 2-1/2 and above, bronze becomes impractical — most manufacturers do not offer flanged bronze above NPS 3 — so the line transitions to cast iron, ductile iron, or steel. Ductile iron is selected over gray cast iron where higher mechanical strength or a Class 150 rating is needed; carbon steel is reserved for steam mains above 15 psig and for hydronic systems above 175 psig. {note}
+
+### Valves NPS 1/4 through NPS 2 shall be bronze or brass for general hydronic, chilled-water, and low-pressure steam service.
+
+### Bronze bodies shall not be specified in flanged configurations above NPS 3; at NPS 2-1/2 and larger the valve shall transition to cast iron, ductile iron, or steel.
+
+### Valves NPS 2-1/2 through NPS 12 in chilled-water, condenser-water, and hot-water-heating mains shall be cast iron or ductile iron of the appropriate pressure class.
+
+### Carbon-steel bodies shall be used for steam mains above 15 psig and for hydronic service above 175 psig, in accordance with ASME B16.34.
+
+```datasheet
+label: Body Material
+type: radio
+options:
+ - Bronze / brass (NPS 1/4–2)
+ - Cast iron Class 125 (NPS 2-1/2–12)
+ - Cast iron Class 250 (NPS 2-1/2–12)
+ - Ductile iron Class 150 (NPS 2-1/2–12)
+ - Carbon steel Class 150/300 (steam, high pressure)
+default: Bronze / brass (NPS 1/4–2)
+```
+
+## End connections. {note}
+
+## End-connection type follows pipe material and joining method. Threaded and solder-joint ends are standard at NPS 2 and smaller; flanged ends are standard at NPS 2-1/2 and larger or wherever a flanged breakout is required for valve removal. Grooved ends apply where mechanical (coupling-style) piping is used. A critical and frequently missed detail: Class 125 cast-iron flanges are drilled to ASME B16.1 and do not share the bolt circle of Class 150 steel flanges to ASME B16.5 in sizes NPS 2-1/2 and NPS 3 — mixing the two without adapter flanges produces a joint that cannot be bolted. {note}
+
+### Valves NPS 2 and smaller shall have threaded ends on steel-pipe systems and solder-joint ends on copper-tube systems, with solder-joint dimensions per ASME B16.18.
+
+### Valves NPS 2-1/2 and larger shall have flanged ends, or grooved ends where mechanical-coupling piping is used.
+
+### Flanged ends shall be specified where a valve must be removable for service without cutting the adjacent pipe.
+
+### Cast-iron Class 125 flanges (ASME B16.1) shall not be bolted directly to Class 150 steel flanges (ASME B16.5) in sizes NPS 2-1/2 and NPS 3; one flange system shall be used throughout or adapter flanges shall be called out on the drawings.
+
+```datasheet
+label: End Connection Type
+type: radio
+options:
+ - Threaded (NPS 2 and smaller, steel pipe)
+ - Solder joint (NPS 2 and smaller, copper tube)
+ - Flanged (NPS 2-1/2 and larger)
+ - Grooved (mechanical-coupling piping)
+default: Threaded (NPS 2 and smaller, steel pipe)
+```
+
+# Gate, Globe, and Check Valves {toc}
+
+## Gate valves. {note}
+
+## Gate valves provide full-bore, low-loss isolation but are unsuited to throttling: a partly open gate vibrates and erodes its seat. The principal selection question after material and class is stem orientation. An outside-screw-and-yoke (OS&Y) rising stem gives a clear visual indication of position and keeps the stem threads out of the fluid, but its travel demands vertical clearance — a real constraint in ceiling plenums and tight mechanical rooms, where a non-rising-stem or inside-screw valve, or a ball valve, may be required instead. {note}
+
+### Bronze gate valves NPS 1/4 through NPS 2 shall conform to MSS SP-80, Class 125 or Class 150, with rising stem and renewable or integral seats.
+
+### Cast-iron gate valves NPS 2-1/2 through NPS 12 shall conform to MSS SP-70, Class 125 or Class 250, OS&Y rising stem, flanged ends, with a bolted bonnet.
+
+### Rising-stem gate valves shall not be installed in ceiling plenums or confined spaces without verifying vertical clearance for full stem travel; a non-rising-stem valve or a ball valve shall be substituted where clearance is inadequate.
+
+```datasheet
+label: Gate Valve Stem Type
+type: radio
+options:
+ - OS&Y rising stem (clear position indication)
+ - Non-rising stem (confined clearance)
+default: OS&Y rising stem (clear position indication)
+```
+
+## Globe valves. {note}
+
+## Globe valves are the manual throttling and coarse-balancing valve of the corpus. Their tortuous flow path imposes a high pressure drop even fully open, which is the price of fine, repeatable throttling control and tight shutoff against a renewable seat and disc. {note}
+
+### Where throttling is needed but pressure drop is critical, the Engineer of Record should evaluate whether a balancing valve under [[sync/hydronic-specialties]] better serves the application than a globe valve.
+
+### Bronze globe valves NPS 1/4 through NPS 2 shall conform to MSS SP-80, Class 125 or Class 150, with a renewable seat and disc.
+
+### Cast-iron globe and angle valves NPS 2-1/2 and larger shall conform to MSS SP-85, Class 125 or Class 250, flanged ends.
+
+### Globe valves used for shutoff shall provide seat leakage not exceeding ANSI/FCI 70-2 Class IV.
+
+## Check valves. {note}
+
+## Check valves prevent reverse flow, most often at pump discharge where reverse rotation on shutdown can damage the pump and impeller. Swing checks are the default for horizontal lines; spring-loaded wafer or silent checks suit vertical-flow-up lines and locations where slam must be controlled. A check valve must be sized and oriented for the actual flow direction and mounting position — a swing check installed in a vertical-down line will not seat. {note}
+
+### Bronze swing check valves NPS 1/4 through NPS 2 shall conform to MSS SP-80, Class 125 or Class 150.
+
+### Cast-iron swing check valves NPS 2-1/2 through NPS 12 shall conform to MSS SP-71, Class 125 or Class 250, flanged ends.
+
+### Check valves shall be selected and installed for the actual service flow direction and mounting orientation; swing checks shall not be installed in vertical-down-flow lines.
+
+```datasheet
+label: Check Valve Style
+type: radio
+options:
+ - Swing check (horizontal lines)
+ - Spring-loaded wafer / silent check (vertical-up, anti-slam)
+default: Swing check (horizontal lines)
+```
+
+# Ball Valves {toc}
+
+## Ball valves are the default small-line isolation valve. {note}
+
+## In NPS 2 and smaller, ball valves have largely displaced gate valves for isolation duty: they are lower in cost, quarter-turn (fast to operate, with obvious open/closed indication from the handle), and far more tolerant of frequent cycling. This Standard treats ball and gate valves as both acceptable for small-line isolation rather than mandating one. The principal ball-valve decision is port size. A full-port ball valve has a bore equal to the pipe ID and imposes negligible pressure drop; a standard- (reduced-) port valve is cheaper but obstructs the line and prevents rod-out. Full port is required in flow-critical and rod-out / pigging-service locations. {note}
+
+### Brass and bronze ball valves NPS 1/4 through NPS 3 shall conform to MSS SP-110, Class 150, with a chrome-plated or stainless ball and a PTFE or RPTFE seat.
+
+### Ball valves for hydronic branch isolation shall be full-port unless the Engineer of Record accepts standard-port for a non-flow-critical location.
+
+### Ball valves in flow-critical, rod-out, or pigging-service locations shall be full-port; standard-port valves shall not be used in these locations.
+
+### Carbon-steel ball valves NPS 1/2 through NPS 2 for steam mains shall be Class 300, with threaded or socket-weld ends, conforming to ASME B16.34.
+
+### Ball valves shall be furnished with a lever handle in sizes NPS 1/4 through NPS 2; a memory stop may be provided where the valve serves a fixed throttling position.
+
+```datasheet
+label: Ball Valve Port
+type: radio
+options:
+ - Full port (flow-critical, rod-out)
+ - Standard / reduced port (non-critical isolation)
+default: Full port (flow-critical, rod-out)
+```
+
+```datasheet
+label: Ball Valve Seat Material
+type: radio
+options:
+ - RPTFE (general hydronic / steam)
+ - PTFE (general hydronic)
+default: RPTFE (general hydronic / steam)
+```
+
+# Butterfly Valves {toc}
+
+## Butterfly valves are the default large-line isolation valve. {note}
+
+## At NPS 2-1/2 and above, butterfly valves are the standard isolation valve for chilled-water, condenser-water, and hot-water mains: they are compact, light, and far cheaper than a flanged gate valve of equal size. MSS SP-67 distinguishes Type I (tight shutoff) from Type II (seating with allowable leakage); HVAC isolation duty calls for Type I. Two construction choices dominate selection — body style (lug versus wafer) and operator (lever versus gear) — and both have well-known failure modes if chosen carelessly. {note}
+
+### Butterfly valves shall conform to MSS SP-67, Type I (tight shutoff), with a resilient seat and a stainless-steel or coated ductile-iron disc.
+
+### Butterfly valves in chilled-water service shall have a one-piece resilient seat that isolates the disc and stem from the line fluid, so that the body sees no corrosion and the disc edge seats against elastomer.
+
+## Body style: lug versus wafer. {note}
+
+## A wafer-body butterfly valve is sandwiched between two flanges and relies on both flanges staying bolted; remove the downstream pipe and a wafer valve can neither hold pressure nor be taken out without dropping the line. A lug-body valve has threaded (tapped) bolt holes on both flanges, so it bolts independently to each side and can serve as a dead-end isolation valve — the downstream side can be opened or removed while the valve holds the upstream pressure. Lug bodies are therefore mandatory at end-of-line, at equipment connections, and wherever the valve isolates a drainable section from the rest of the system. {note}
+
+### Butterfly valves at end-of-line, at equipment connections, and wherever the valve must isolate a drainable or removable section shall be lug-body with tapped holes on both flanges.
+
+### Wafer-body butterfly valves shall be used only at in-line locations where both adjacent flanges remain permanently bolted; they shall not be used as dead-end or equipment-isolation valves.
+
+```datasheet
+label: Butterfly Body Style
+type: radio
+options:
+ - Lug body (dead-end, equipment isolation)
+ - Wafer body (in-line only)
+default: Lug body (dead-end, equipment isolation)
+```
+
+## Operator selection. {note}
+
+## Resilient-seated butterfly valves have high breakaway torque because the disc edge must compress the elastomer seat. In small sizes a lever (handle with a notched plate) is adequate; in larger sizes the breakaway torque exceeds what one person can safely apply to a lever, and lever operation tears the seat and risks operator injury. A worm-gear operator with a handwheel multiplies torque and holds position. Gear operators are required at NPS 8 and larger by MSS SP-67, and are commonly specified from NPS 6 up for high-torque EPDM-seated valves. {note}
+
+### Butterfly valves NPS 2-1/2 through NPS 4 may be furnished with a lever (notched-plate) operator.
+
+### Butterfly valves NPS 8 and larger shall be furnished with a gear operator and handwheel in accordance with MSS SP-67.
+
+### Butterfly valves NPS 6 shall be furnished with a gear operator where the manufacturer's published breakaway torque exceeds the safe manual lever torque, which is typical for EPDM-seated valves.
+
+```datasheet
+label: Butterfly Valve Operator
+type: radio
+options:
+ - Lever / notched plate (NPS 2-1/2–4)
+ - Gear operator with handwheel (NPS 6+)
+default: Gear operator with handwheel (NPS 6+)
+```
+
+```datasheet
+label: Butterfly Disc Material
+type: radio
+options:
+ - Stainless-steel disc
+ - Coated ductile-iron disc
+default: Stainless-steel disc
+```
+
+# Operators, Drains, and Accessories {toc}
+
+## Operator type and reach. {note}
+
+## Valves mounted out of reach must be operable from the floor. Valves whose centerline is above roughly 7 ft above finished floor (AFF) require a chainwheel operator with a chain hanging within reach, unless a permanent platform or catwalk gives access. Selecting a chainwheel at design time avoids a field retrofit and the safety hazard of operating a high valve from a ladder. {note}
+
+### Valves whose operator is more than 2.1 m (7 ft) above finished floor, and not accessible from a permanent platform, shall be furnished with a chainwheel operator and a chain reaching to 1.8 m (6 ft) AFF.
+
+### Handwheel and lever operators shall open counterclockwise and shall carry a cast or stamped open/close direction indication.
+
+```datasheet
+label: Operator Type
+type: radio
+options:
+ - Lever handle (ball / small butterfly)
+ - Handwheel (gate / globe)
+ - Gear operator with handwheel (large butterfly)
+ - Chainwheel (operator above 7 ft AFF)
+default: Lever handle (ball / small butterfly)
+```
+
+## Drain and vent provisions. {note}
+
+## A drainable section needs a drain at its low point and a vent at its high point, or it cannot be emptied for service without improvised field connections — a recurring source of RFIs. Provide a hose-end (hose-bib) drain valve at system low points and at equipment isolation valve groups so the isolated section can be drained to a hose. Tee-head plugs serve where a hose connection is not needed. {note}
+
+### A hose-end drain valve shall be provided at each system low point and at each equipment isolation valve group so the isolated section can be drained.
+
+### Drain valves shall be bronze ball valves, NPS 1/2 or NPS 3/4, with a threaded hose-end outlet and a cap or plug.
+
+```datasheet
+label: Drain Valve Size
+type: radio
+options:
+ - "NPS 1/2 hose-end ball valve"
+ - "NPS 3/4 hose-end ball valve"
+default: "NPS 3/4 hose-end ball valve"
+```
+
+# Identification and Tagging {toc}
+
+## Valve tags. {note}
+
+## Every isolation and shutoff valve must carry a permanent tag keyed to the owner's valve schedule and P&ID, so an operator can find and identify a valve years after construction. Tags are stamped metal discs attached with wire or chain — adhesive labels are not acceptable in mechanical-room environments. {note}
+
+### Each isolation, shutoff, and drain valve shall be tagged with a stamped brass or stainless-steel disc, not less than 19 mm (3/4 in.) in diameter.
+
+### Tags shall be stamped with the valve's system and valve number corresponding to the project P&ID and the owner's valve schedule.
+
+### Tags shall be attached to the valve operator or body with 20-gauge wire, bead chain, or a stainless-steel band; adhesive labels shall not be used.
+
+### The Contractor shall coordinate the valve-numbering scheme with the owner's valve schedule before tags are fabricated. [[drawing: valve schedule / P&ID]]
+
+```datasheet
+label: Valve Tag Material
+type: radio
+options:
+ - Stamped brass disc
+ - Stamped stainless-steel disc
+default: Stamped brass disc
+```
+
+```datasheet
+label: Valve Tag Diameter
+type: range
+unit: mm
+min: 19
+max: 38
+step: 3
+default: 19
+```
+
+# Testing {toc}
+
+## Factory testing. {note}
+
+## Every valve is pressure-tested at the factory before shipment, and MSS SP-61 is the common test reference across all the valve types in this Standard. Two tests matter: the shell test, which proves the body and bonnet hold pressure with the valve partly open, and the seat (closure) test, which proves the closed valve does not leak past the seat. Acceptance leakage differs by type — bubble-tight (zero drops) for ball and gate valves, a defined allowance per ANSI/FCI 70-2 Class IV for globe shutoff valves. {note}
+
+### Each valve shall pass a factory hydrostatic shell test at 1.5 times the cold working pressure (CWP) in accordance with MSS SP-61, with no leakage through the body or bonnet.
+
+### Each valve shall pass a factory seat (closure) test at 1.1 times the CWP in accordance with MSS SP-61, held for not less than one minute.
+
+### Ball and gate valves shall demonstrate bubble-tight (zero-leakage) seat performance at the seat-test pressure.
+
+### Globe shutoff valves shall demonstrate seat leakage not exceeding ANSI/FCI 70-2 Class IV.
+
+### Butterfly valves furnished as Type I shall demonstrate tight shutoff in accordance with MSS SP-67 Type I.
+
+## Field testing. {note}
+
+## After installation the valves are proved as part of the piping-system hydrostatic test, performed under [[sync/hydronic-piping]]. Valves are not the subject of a separate field pressure test; position and joint integrity are verified as part of the system test per the clauses below. {note}
+
+### Valves shall be in the open position during the piping-system hydrostatic test, except where a valve is the boundary of the test section.
+
+### Each valve joint — threaded, soldered, flanged, or grooved — shall be verified free of leakage during the piping-system hydrostatic test.
+
+### Any valve found to leak past the seat or through the body during system testing shall be repaired or replaced and re-tested.
+
+# Installation {toc}
+
+## Access and orientation. {note}
+
+## A valve that cannot be reached, read, or removed is a maintenance liability. Orientation matters: directional valves (check valves, some butterfly seats) follow the flow arrow, and butterfly discs need clearance to swing fully into the adjacent pipe. {note}
+
+### Valves shall be installed with their operators accessible and their open/close indication visible from the normal operating position.
+
+### Valves shall be installed so they can be serviced, repacked, or removed without cutting pipe or removing adjacent equipment.
+
+### Directional valves shall be installed with the body flow arrow oriented to the service flow direction.
+
+### Butterfly valves shall be installed with clearance for the disc to rotate fully open into the adjacent pipe, and shall be cycled to full open before the adjacent flanges are finally tightened.
+
+### Flanged and grooved joints shall be made up to the valve manufacturer's published bolt torque or coupling specification.
+
+## Isolation completeness. {note}
+
+### An isolation valve shall be provided at each branch takeoff from a main so the branch can be isolated without shutting down the main.
+
+### A shutoff valve shall be provided at each connection to HVAC equipment in accordance with ASHRAE 90.1 Section 6.4, sized to the equipment connection.
+
+### A drainable section shall be bounded by isolation valves and provided with a drain at its low point, so it can be emptied without draining the full system.
+
+## Insulation coordination. {note}
+
+### Valve bodies in insulated chilled-water and condenser-water piping shall be insulated with removable, reusable insulation covers, vapor-sealed to prevent condensation on the body.
+
+### Valve bodies in insulated hot-water and steam piping shall be insulated to the system insulation thickness; operator stems and handwheels shall remain accessible through the insulation.
+
+# Delivery, Storage, and Handling {toc}
+
+## Protection before installation. {note}
+
+### Valves shall be delivered with end protectors in place and with the valve in the position recommended by the manufacturer for shipment.
+
+### Valves shall be stored under cover, off the ground, and protected from dirt, moisture, and freezing until installed.
+
+### Resilient seats and elastomer trim shall be protected from sunlight, ozone, and petroleum products during storage.
+
+### Valves shall be handled by the body, never by the operator, handwheel, or stem.
+
+# Warranty {toc}
+
+## Manufacturer warranty. {note}
+
+### Each valve shall carry the manufacturer's standard warranty against defects in materials and workmanship for not less than one year from substantial completion.
+
+### Repairable valve types (gate, globe, repairable ball) shall be warranted to accept renewal of seats, discs, and packing using standard manufacturer repair parts.
+
+```datasheet
+label: Warranty Period
+type: range
+unit: years
+min: 1
+max: 5
+step: 1
+default: 1
+```
+
+# Spare Parts {toc}
+
+## Spares and consumables. {note}
+
+## Hand over the seat kits, packing, and operators the owner will need for routine maintenance, so a leaking stem or worn seat can be repaired without sourcing obsolete parts years later. {note}
+
+### The Contractor shall furnish to the owner one stem-packing set and one seat/disc renewal kit for each repairable valve type and size installed in quantities of five or more.
+
+### The Contractor shall furnish one spare gear operator, or operator repair kit, for each gear-operated butterfly valve size NPS 8 and larger.
+
+```datasheet
+label: Spare Parts Provided
+type: checkbox
+options:
+ - Stem-packing sets (per repairable valve type/size)
+ - Seat / disc renewal kits (per repairable valve type/size)
+ - Gear operator repair kit (NPS 8+ butterfly)
+default:
+ - Stem-packing sets (per repairable valve type/size)
+ - Seat / disc renewal kits (per repairable valve type/size)
+```