SynC™

SynC · Editorial revision

Air Release and Vacuum Valves

Revision1
EditedOct 12, 2026
StatusCurrent
Contents

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Current revision. This is editorial revision 1, the current text of this standard. Read it on the standard's page.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Initial publication

1 Scope

NOTE This standard covers the valves that let air out of and into a pressure pipeline: the air release valve that vents the small volumes of air that collect at a high point while the line is under pressure, the air/vacuum valve that exhausts the whole pipe volume of air while the line fills and admits air while it drains, and the combination air valve that does both in one body or in a dual-body assembly, built to AWWA C512 for water, wastewater, reclaimed water, and sludge service. (1.1)
NOTE The boundary of the work is the valve as a shop-assembled unit with its isolation valve, its backflushing accessories where furnished, its slow-closing or surge-check device where furnished, and its shop coating, together with the installation of the unit at the high point, the vent to atmosphere, the drain, and the freeze protection that keep it working, and the tests that prove it. (1.2)
NOTE This standard is read with Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process, which carries the submittal register and review workflow, the factory and witnessed test policy, manufacturer's field services, the manufacturer's data nameplate, the spare parts basis, anchorage, and the other administrative and execution provisions every process valve inherits; nothing in those articles is restated here. (1.3)
NOTE Air is the one thing a pressure pipeline always contains and never shows on a profile. It comes out of solution as the pressure falls along the line, it enters at every pump start and every draindown, and it collects at each high point as a pocket that narrows the flow area until a pump that made its flow at startup cannot make it a year later. A line that drains faster than air can enter it pulls a vacuum that a thin-walled pipe collapses under. The air valve is a small, inexpensive component whose failure is seldom seen until the pipeline it protects has failed, which is why this standard is prescriptive about the sizing basis, the float and orifice, the wastewater pattern, and the vent, and permissive about the materials and the enclosure the engineer selects by location. (1.4)
1.5 Air valves shall conform to AWWA C512 and shall be sized in accordance with AWWA M51 for the filling rate, the draining rate, and the working pressure stated for each location.
1.6 Air valves in potable water service shall be certified to NSF/ANSI/CAN 61 and NSF/ANSI/CAN 372 for every wetted component, including the body coating, the float, the seat, and the lubricants.
NOTE The location of every air valve, its type, and the hydraulic conditions it is sized from are decided by the engineer who laid out the pipeline, not by this standard. Inside the plant fence the process piping drawings carry that decision; on a site sewage force main Sanitary Sewer SystemsSanitary Sewer Systems (Site)Resolves to the current adopted revision.sync/sanitary-sewer-systems decides whether each high point carries a combination valve, an air release valve, or no valve at all, and furnishes the vault; on a site water main Water Distribution PipingSite Water Distribution PipingResolves to the current adopted revision.sync/water-distribution-piping and Site UtilitiesSite UtilitiesResolves to the current adopted revision.sync/site-utilities furnish the valves on the main. Where the drawings designate an air valve on a site main to be furnished under this standard, this standard furnishes the product and governs its installation in the enclosure the site standard provides. (1.7)
NOTE Where a pump standard furnishes an air release valve as part of the pump or the pump station package, that standard governs the valve furnished with the package, and this standard governs every air valve shown separately on the process and instrumentation diagrams. (1.8)
NOTE The following are outside this scope and are governed by the companion standards named. (1.9)
  • The force-main air valve decision and the air valve vaults on a site sewage force main: Sanitary Sewer SystemsSanitary Sewer Systems (Site)Resolves to the current adopted revision.sync/sanitary-sewer-systems
  • The site water main and its valves: Water Distribution PipingSite Water Distribution PipingResolves to the current adopted revision.sync/water-distribution-piping and Site UtilitiesSite UtilitiesResolves to the current adopted revision.sync/site-utilities
  • The process piping, its outlets and taps, its flange bolting and gaskets, and its pressure test: Ductile Iron Process PipingDuctile Iron Process PipingResolves to the current adopted revision.sync/ductile-iron-process-piping, Steel And Stainless Process PipingSteel and Stainless Steel Process PipingResolves to the current adopted revision.sync/steel-and-stainless-process-piping, and Plastic Process PipingPlastic Process PipingResolves to the current adopted revision.sync/plastic-process-piping
  • Isolation valves as products: Resilient Seated Gate ValvesResilient-Seated Gate ValvesResolves to the current adopted revision.sync/resilient-seated-gate-valves, Eccentric Plug ValvesEccentric Plug ValvesResolves to the current adopted revision.sync/eccentric-plug-valves, and Butterfly ValvesButterfly ValvesResolves to the current adopted revision.sync/butterfly-valves; process check valves: Process Check ValvesProcess Check ValvesResolves to the current adopted revision.sync/process-check-valves
  • Valves inside a packaged lift station: Packaged Pump StationsPackaged Pump and Lift StationsResolves to the current adopted revision.sync/packaged-pump-stations; inside a building ejector package: Sump And Sewage PumpsSump and Sewage PumpsResolves to the current adopted revision.sync/sump-and-sewage-pumps
  • Air vents, air separators, and vacuum relief in building hydronic systems: Hydronic SpecialtiesHydronic SpecialtiesResolves to the current adopted revision.sync/hydronic-specialties and Expansion Tanks And Air SeparatorsExpansion Tanks and Air SeparatorsResolves to the current adopted revision.sync/expansion-tanks-and-air-separators; in domestic water piping: Domestic Water PipingDomestic Water PipingResolves to the current adopted revision.sync/domestic-water-piping and Plumbing Piping ValvesGeneral-Duty Valves for Plumbing PipingResolves to the current adopted revision.sync/plumbing-piping-valves
  • Vacuum breakers for backflow protection: Backflow PreventionBackflow PreventionResolves to the current adopted revision.sync/backflow-prevention
  • The air release valve on a fire pump and the air vent on a sprinkler system: Fire PumpsFire PumpsResolves to the current adopted revision.sync/fire-pumps and Wet Pipe Fire Sprinkler SystemsWet-Pipe Fire Sprinkler SystemsResolves to the current adopted revision.sync/wet-pipe-fire-sprinkler-systems
  • Common process administrative and execution provisions: Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process
  • Field-applied finish coat systems: High Performance CoatingsHigh-Performance CoatingsResolves to the current adopted revision.sync/high-performance-coatings; valve tags and piping identification: Mechanical IdentificationMechanical IdentificationResolves to the current adopted revision.sync/mechanical-identification
NOTE Pressure relief valves, surge anticipator valves, and pressure regulating valves are not yet owned by a SynC standard. (1.10)

2 Referenced Standards

2.1 Valves, accessories, coatings, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the Contract Documents, the adopted codes, and a referenced standard differ on the same matter, the most stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
AWWA C512 Air-Release, Air/Vacuum, and Combination Air Valves for Water and Wastewater Service
AWWA M51 Air Valves: Air-Release, Air/Vacuum, and Combination
AWWA C550 Protective Interior Coatings for Valves and Hydrants
AWWA C504 Rubber-Seated Butterfly Valves, 3 In. Through 72 In.
AWWA C509 Resilient-Seated Gate Valves for Water Supply Service
AWWA C517 Resilient-Seated Cast-Iron Eccentric Plug Valves
ASME B1.20.1 Pipe Threads, General Purpose (Inch)
ASME B16.1 Gray Iron Pipe Flanges and Flanged Fittings: Classes 25, 125, and 250
ASME B16.42 Ductile Iron Pipe Flanges and Flanged Fittings: Classes 150 and 300
ASTM A126 Gray Iron Castings for Valves, Flanges, and Pipe Fittings
ASTM A240 / A240M Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications
ASTM A276 / A276M Stainless Steel Bars and Shapes
ASTM A351 / A351M Castings, Austenitic, for Pressure-Containing Parts
ASTM A536 Ductile Iron Castings
ASTM D2000 Classification System for Rubber Products in Automotive Applications
ASTM F593 Stainless Steel Bolts, Hex Cap Screws, and Studs
MSS SP-25 Standard Marking System for Valves, Fittings, Flanges, and Unions
NSF/ANSI/CAN 61 Drinking Water System Components: Health Effects
NSF/ANSI/CAN 372 Drinking Water System Components: Lead Content

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for the Engineer of Record's review and return before any air valve is released for manufacture:
  • Product data for each valve type, size, pressure class, and service, identifying the AWWA C512 type, the body, cover, float, seat, orifice, and trim materials with their ASTM designations, the inlet and outlet connections, and the orifice diameter
  • An air valve schedule keyed to the tag numbers on the drawings, listing for each valve its location, type, inlet size, orifice diameter, pressure class, service, pattern, isolation valve, accessories, and exposed or vault installation
  • Sizing calculations for each air/vacuum and combination valve, stating the filling rate and the draining rate taken from the piping profile, the allowable differential across the large orifice during filling, the collapse differential of the connected pipe, and the resulting air exhaust and inflow capacities, with the manufacturer's published capacity curves marked at those points
  • Sizing calculations for each air release valve, stating the working pressure at the valve and the orifice diameter the float opens at that pressure
  • Dimensioned drawings for each valve showing the inlet and outlet connections, the overall height with the isolation valve and the backflushing accessories, the removal clearance, and the vent connection
  • Product data for the isolation valve, the backflushing accessories, and the slow-closing or surge-check device furnished with each valve
  • Coating product data, including the AWWA C550 compliance statement, the dry film thickness, and the NSF/ANSI/CAN 61 listing where the valve is in potable water service
  • Product data for the vault, the vent piping and its termination, and the freeze protection for each air valve on a buried line within the plant
  • A field test plan identifying the filling observation, the seat leakage observation, and the record form
Action Submittals Requiredcheckbox
☑ Valve product data by type, size, class, and service
☑ Air valve schedule keyed to drawing tags
☑ Air/vacuum and combination valve sizing calculations with capacity curves
☑ Air release valve orifice sizing calculations
☑ Dimensioned valve drawings with removal clearance
☑ Isolation valve, accessory, and surge device product data
☑ Coating product data
☐ Vault, vent, and freeze protection product data
☑ Field test plan
3.1.2 Manufacture of a valve shall not begin until the submittal covering that valve has been returned by the Engineer of Record.
NOTE The sizing calculation is the submittal that catches the most errors on this product, because a valve that is correct in every material still fails when its large orifice was picked from the pipe size alone and the line drains twice as fast as the orifice admits air. Reviewing the filling and draining rates against the profile, valve by valve, is cheaper than a collapsed pipe. (3.1.3)

3.2 Closeout Submittals

3.2.1 The Contractor shall submit the following at substantial completion, before the air valves are accepted:
  • Certified factory test reports for every valve, identified by serial number, recording the shell test and the seat leakage test with their pressures, durations, and results
  • Signed and dated field test records for every valve, recording the filling observation, the seat leakage observation at working pressure, and the operation of the isolation valve and the backflushing accessories
  • Record drawings locating every air valve on a buried line by tie dimensions to permanent surface features, with the vault and vent location and the depth to the valve inlet
  • Operation and maintenance data for each valve type and size, including the backflushing procedure for wastewater valves, float and seat replacement, and the winter procedure for every valve with freeze protection
  • Coating inspection records recording the dry film thickness and the holiday test result for each valve
  • Spare parts receipt signed by the Owner's representative
  • Warranty documentation
Closeout Submittals Requiredcheckbox
☑ Certified factory test reports by serial number
☑ Field test records
☑ Record drawings with vault ties and depth
☑ Operation and maintenance data with backflushing and winter procedures
☐ Coating inspection records
☐ Spare parts receipt
☑ Warranty documentation

4 Quality Assurance

4.1 Manufacturer Qualifications

4.1.1 Air valves shall be the product of a manufacturer that has produced valves to AWWA C512 of the type and pattern furnished and has valves of the same type, size range, and pattern in water or wastewater service in North America, for the experience term and the reference installation count indicated under Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process.
4.1.2 The manufacturer shall furnish an affidavit of compliance with AWWA C512 for each valve type and size furnished.
4.1.3 Replacement floats, seats, orifice assemblies, and backflushing accessories shall be available from the manufacturer for not less than the parts availability term indicated under Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process.

4.2 Single-Source Responsibility

4.2.1 Air valves of every type on the project shall be the product of a single manufacturer.
4.2.2 Each air valve, its isolation valve, its backflushing accessories, and its slow-closing or surge-check device shall be furnished and assembled by the air valve manufacturer as a unit, and the manufacturer shall be responsible for the match between the valve and the device.
NOTE A surge-check device that closes at a lower air velocity than the valve above it exhausts leaves the line filling against a closed valve, and a backflush valve of the wrong size leaves the operator unable to clear a fouled float. The air valve manufacturer is the only party who knows the exhaust velocity of its own valve, so the device is matched where that number is known. (4.2.3)

4.3 Marking

4.3.1 Each valve shall carry the markings AWWA C512 and MSS SP-25 require, cast or on a permanently attached corrosion-resistant nameplate, including the manufacturer, the valve type, the inlet size, the orifice diameter where the valve has a small orifice, the pressure class, and the year of manufacture.
4.3.2 Each wastewater-pattern valve shall additionally be marked for wastewater service on the nameplate.

5 Service Conditions

5.1 Location and Sizing Basis

5.1.1 The location, tag, type, and service fluid of each air valve, and the filling rate, the draining rate, and the working pressure it is sized from, shall be as indicated on the piping profile and the valve schedule.
5.1.2 The filling rate from which the large orifice is sized shall be the rate at which the pipeline is filled under the filling procedure the piping standard governing the line prescribes, and the draining rate shall be the rate at which the line drains by gravity through the drain, the break, or the pump shown on the profile, whichever is greatest.
5.1.3 Air valves shall be rated for the working pressure stated for their location and for the surge pressure the piping standard governing the line designs the pipe for.
NOTE Location and sizing conditions are properties of each high point on a project, and a standard that asserts either has decided the hydraulics. The profile carries the elevation, the reach it drains, and the rate the engineer fills the line at, and this standard carries what every valve of a given type and pattern has in common. (5.1.4)

5.2 Service Fluid and Pattern

5.2.1 Air valves in raw water, treated water, reclaimed water, and clean industrial water service shall be of the water pattern.
5.2.2 Air valves in wastewater, sludge, scum, and any other service that carries grease, solids, or sewage gas shall be of the wastewater pattern, and a water-pattern valve shall not be installed in those services.
NOTE A water-pattern valve has a short body and a float that sits at the liquid surface, and in sewage the float fouls with grease and rags within weeks and the orifice plugs with the first stringy solid that reaches it. The wastewater pattern keeps the float well above the liquid in a tall body, gives the operator a connection to flush the body with clean water without removing the valve, and is built of materials that survive hydrogen sulfide. The pattern follows the fluid at each valve, which the valve schedule carries. (5.2.3)

5.3 Ambient Conditions

5.3.1 Valves, accessories, and vent terminations installed outdoors or in an unheated enclosure shall be rated by their manufacturers for continuous service at Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum and at Site Ambient Temperature MaximumSite Ambient Temperature MaximumParameterEach project supplies its own value.site-ambient-temperature-maximum.
5.3.2 Valves installed in a vault whose floor is below Seasonal High Groundwater ElevationSeasonal High Groundwater ElevationParameterEach project supplies its own value.seasonal-high-groundwater-elevation shall have their outlet and vent arranged so that groundwater entering the vault cannot reach the outlet.
NOTE A vault below the water table floods, and an air valve whose outlet is under water admits water instead of air on the next draindown and discharges into a flooded vault on the next fill. The groundwater elevation is a project fact, and the outlet arrangement follows it. (5.3.3)

6 Valve Types

6.1 Air Release Valves

6.1.1 An air release valve shall vent air that collects in the valve body under pressure through a small orifice that a float opens as air displaces the liquid in the body and closes as the liquid returns, and shall seal drop-tight at the working pressure with the body full.
6.1.2 The orifice of each air release valve shall be sized so that the float opens it at the maximum working pressure at the valve, and the valve shall be furnished with the orifice diameter the sizing calculation establishes.
NOTE The float of an air release valve opens the orifice by its own weight against the line pressure acting on the orifice area, so a given float opens a smaller orifice as the pressure rises. The orifice is the one dimension of this valve that is selected per location, and a valve whose orifice is too large for its pressure never opens. (6.1.3)
6.1.4 Air release valves shall be furnished with a mechanism that opens the orifice by lever action or by a direct float, and the orifice shall be positioned so that the float and the linkage are out of the discharging air stream.

6.2 Air/Vacuum Valves

6.2.1 An air/vacuum valve shall exhaust air through a large orifice as the line fills, shall close when liquid lifts the float to the seat, shall remain closed under line pressure, and shall admit air through the same orifice as the line drains.
6.2.2 An air/vacuum valve shall not reopen under line pressure to vent the air that collects after the line is full.
6.2.3 Each air/vacuum valve shall exhaust air at the filling rate stated for its location with a differential across the valve not exceeding the value indicated in the datasheet.
Differential Across the Large Orifice During Fillingrange
psi
1235
Default: Not more than 2 psi
NOTE Two psi is the exhaust differential AWWA M51 sizes against and the one nearly every waterworks specification carries, because a float that has to close against a stronger exhaust stream closes early and traps the air it was meant to vent. A lower differential buys a larger valve for a line that is filled quickly; a higher differential is accepted where the valve is sized for a draindown rate far beyond its filling rate and the filling condition no longer governs. (6.2.4)
6.2.5 Each air/vacuum valve shall admit air at the draining rate stated for its location with a differential across the valve not exceeding 5 psi and not exceeding the differential at which the connected pipe collapses, whichever is less.
NOTE Air admission is sized to the pipe wall rather than to the water. A ductile iron pipe withstands a full vacuum; a thin-walled steel or a large plastic pipe collapses at a few psi below atmospheric, and the valve that protects it has to admit air at the draindown rate before the pressure in the pipe falls that far. The collapse differential is a property of the pipe the piping standard furnishes, and the sizing calculation states it. (6.2.6)

6.3 Combination Air Valves

6.3.1 A combination air valve shall perform the functions of an air/vacuum valve and an air release valve in one unit, and shall be of the arrangement indicated in the datasheet.
Combination Valve Arrangementradio
○ Single body, large and small orifices in one valve
○ Dual body, air/vacuum valve with a separate air release valve piped to it
NOTE A single-body valve carries both orifices in one casting, is the shorter and lighter unit, and is what the small sizes are built as. A dual-body assembly bolts a separate air release valve to the side of an air/vacuum valve, so each orifice is serviced and replaced on its own and the air release valve is isolated without taking the large orifice out of service, and it is what the large sizes are built as. Each manufacturer builds each size one way or the other, and a project that standardizes on one does so to match its stock of spares. (6.3.2)
6.3.3 Where a dual-body arrangement is furnished, the air release valve shall be furnished with its own isolation valve between it and the air/vacuum valve body.

6.4 Vacuum-Only Service

6.4.1 Where the valve schedule designates a valve to admit air only, the valve shall be an air/vacuum valve furnished with a non-return device on its outlet that admits air freely and prevents exhaust.
NOTE A valve that admits air but never exhausts it is placed where a draindown would collapse the pipe but an exhaust through a large orifice would slam the valve or spray the vault, as at the discharge of a pump that starts against an empty column. The air it admits is vented at the next high point. (6.4.2)

7 Wastewater Pattern

7.1 Body and Float Arrangement

7.1.1 Wastewater-pattern valves shall have an elongated body in which the float at its normal operating level is above the highest liquid level the valve body sees during operation, with the orifice and the linkage above the float.
7.1.2 Wastewater-pattern valves shall have internal surfaces free of pockets and ledges on which grease or solids can lodge, and the float shall be of a shape that does not trap solids on its upper surface.

7.2 Backflushing Accessories

7.2.1 Each wastewater-pattern valve shall be furnished with the backflushing accessories indicated in the datasheet, assembled to the valve by the manufacturer.
Backflushing Accessories on Wastewater-Pattern Valvescheckbox
☑ Backflush inlet valve with a quick-disconnect hose coupling
☑ Blow-off valve at the bottom of the body
☐ Clean water inlet valve at the top of the body
☐ Flushing hose with nozzle and coupling, one per vault
NOTE The backflush inlet and the blow-off are the two connections that let an operator close the isolation valve, drive clean water through the body, and drain the body to the vault without unbolting anything, and together they are what every wastewater air valve is furnished with. A clean water inlet at the top lets the flush reach the orifice and the float from above and is furnished where the plant has a water line at the vault. A flushing hose kept in the vault is furnished by owners whose crews would otherwise arrive without one. (7.2.2)
7.2.3 Backflushing accessory valves shall be full-port ball valves of stainless steel or bronze, with the hose coupling of the Owner's standard pattern.
7.2.4 The Contractor shall furnish the backflushing accessory valves with the air valve, and the piping standard governing the line shall furnish the clean water supply to the vault where one is shown.

8 Pressure Class and Sizing

8.1 Pressure Class

8.1.1 Each air valve shall be of the pressure class indicated in the datasheet.
Pressure Classrange
psi
150300600
Per drawings — the valve schedule (deferred by default)
NOTE The 150 psi class covers nearly every treatment plant yard line and sewage force main, and the 300 psi class is selected on a high-head pump discharge or a transmission main whose static head and surge together exceed 150 psi. A 600 psi valve is a manufacturer's rating beyond the classes AWWA C512 defines, bought for a high-pressure industrial line or a deep-well discharge, and it is furnished to the manufacturer's published rating with the AWWA C512 tests applied at the rated pressure. The class is a property of each line on the project, which the valve schedule carries. (8.1.2)
8.1.3 Where a valve is rated above 300 psi, the manufacturer shall publish the rating and shall apply the shell and seat tests of AWWA C512 at that rating.
8.1.4 A valve in a line that is pumped shall be rated for the shutoff head of the pump at the valve location, including the surge the piping standard designs for.

8.2 Air/Vacuum and Combination Valve Inlet Size

8.2.1 The inlet size of each air/vacuum and combination valve shall be as indicated in the datasheet.
Air/Vacuum and Combination Valve Inlet Sizerange
in. NPS
0.50.75123468101214161820
Derived — the filling rate and the draining rate stated on the piping profile, the allowable filling differential, and the collapse differential of the connected pipe, per AWWA M51 and the manufacturer's capacity curves (by default)
NOTE The inlet size of an air/vacuum valve is the size that passes the required air flow at the allowable differential on the manufacturer's capacity curve, and it is not selected from the pipe size. A rule of thumb that puts a 2 in. valve on a 12 in. main exists, and it is wrong whenever the main drains fast, which is exactly when the valve matters. The size is derived because the same filling rate, draining rate, and differentials yield the same valve from any manufacturer's curve. (8.2.2)
8.2.3 The outlet of the tee or the tapping saddle on which the valve is mounted shall be not smaller than the valve inlet, and the isolation valve beneath the air valve shall be full port and of the same size as the valve inlet.

8.3 Air Release Orifice Diameter

8.3.1 The orifice diameter of each air release valve, and of the small orifice of each combination valve, shall be as indicated in the datasheet.
Air Release Orifice Diameterrange
in.
0.06250.093750.1250.156250.18750.218750.250.31250.3750.43750.5
Derived — the maximum working pressure at the valve and the float's opening force, per the manufacturer's published orifice selection for that pressure (by default)
NOTE Each manufacturer publishes, for each float, the largest orifice that float opens at each pressure, and the orifice is selected as the largest one that opens at the maximum working pressure at the valve, because a larger orifice vents more air per opening and a float that cannot lift it vents nothing. The value is derived because the pressure and the published table yield one answer. (8.3.2)
8.3.3 The inlet size of air release valves shall be not less than 1/2 in. and shall be the inlet the manufacturer furnishes for the orifice selected.

9 Body, Float, Seat, and Trim

9.1 Body Material, Water-Pattern Valves

9.1.1 The body and cover material of water-pattern valves shall be as indicated in the datasheet.
Body Material, Water-Pattern Valvesselect
Gray cast iron, ASTM A126 Class B
Ductile iron, ASTM A536
Stainless steel, ASTM A351 Grade CF8M or ASTM A240 Type 316
Glass-reinforced nylon, valves 2 in. and smaller
NOTE Gray cast iron is the body AWWA C512 is written around and the one every manufacturer stocks in every size, at the lowest cost, and an air valve body carries little bolting stress and no bending, so the ductility that moves a plug valve or a butterfly valve to ductile iron is not needed here. Ductile iron is selected where the utility has standardized its valve inventory on it or where the valve is bolted to a steel flange that would overstress a gray iron flange. A stainless steel body removes the coating as a maintenance item and is selected in a chemical room, a seawater or brine line, or a plant whose standard is stainless wetted parts, at several times the cost. A glass-reinforced nylon body is light, does not corrode, and is built only in the small sizes, where it serves a plastic chemical line or a small reclaimed water line. (9.1.2)
9.1.3 Glass-reinforced nylon bodies shall be furnished only on valves 2 in. and smaller, shall be rated by the manufacturer for the pressure class at the maximum service temperature, and shall be protected from ultraviolet exposure where installed outdoors.

9.2 Body Material, Wastewater-Pattern Valves

9.2.1 The body and cover material of wastewater-pattern valves shall be as indicated in the datasheet.
Body Material, Wastewater-Pattern Valvesselect
Gray cast iron, ASTM A126 Class B, epoxy coated inside and out
Ductile iron, ASTM A536, epoxy coated inside and out
Stainless steel, ASTM A351 Grade CF8M or ASTM A240 Type 316
NOTE The inside of a wastewater air valve body is wetted by sewage at the bottom and bathed in hydrogen sulfide at the top, which is the atmosphere that turns an iron casting to rust and a coating holiday to a hole. A coated cast iron body is the lowest cost and serves where the valve is backflushed on a schedule and the coating is inspected with it; a coated ductile iron body is selected for the same reasons as on the water pattern; a stainless steel body carries no coating to fail and is what the operators who have replaced a rusted-through iron body specify afterward, at a premium that is small against the vault the valve sits in. No material is the norm across the owners who buy this valve, so none is defaulted. (9.2.2)

9.3 Float

9.3.1 Floats shall be of the material indicated in the datasheet, shall be hollow and seamlessly formed or welded and then tested, and shall withstand the shell test pressure of the valve without deformation.
Float Materialselect
Type 316 stainless steel
Type 304 stainless steel
Foamed polypropylene or polyethylene, valves 2 in. and smaller
NOTE The float is the part that spends its life at the liquid surface, alternately wetted and dried, and in a wastewater valve it is coated with grease and struck by the backflush. A Type 316 stainless steel float resists chloride pitting and sulfide attack and is what nearly every specification calls for in both patterns, at a small premium over Type 304, which serves treated water where chlorides are low. A foamed polymer float is furnished in small plastic-bodied valves, where it cannot be crushed by the pressure the valve is rated for, and it is not used in a wastewater valve, where grease adheres to it. (9.3.2)
9.3.3 Floats shall be guided so that they cannot rotate or wedge in the body and shall be free to rise to the seat from any position.

9.4 Seat and Orifice

9.4.1 The seat against which the float or the orifice button seals shall be of the elastomer indicated in the datasheet, retained so that it cannot be dislodged by the exhausting air or the backflush.
Seat Elastomerselect
Nitrile (Buna-N)
EPDM
Fluoroelastomer
Neoprene
NOTE The seat is the only part of the valve that seals, and the air valve seals thousands of times a year, so its compound is matched to the fluid first. Nitrile resists grease, oil, and hydrocarbons and swells slowly in chloraminated water, which makes it the usual seat in wastewater and raw water and a poor one downstream of chloramination. EPDM resists chlorine and chloramine and ozone and is attacked by grease, which makes it the usual seat in treated and potable water and a poor one in sewage. Fluoroelastomer resists chemicals that attack both and is selected for chemical feed and industrial service at several times the cost. Neoprene sits between nitrile and EPDM on both counts and is specified where a utility's stock is neoprene. No compound is the norm across the services this standard covers, so none is defaulted. (9.4.2)
9.4.3 Seats in potable water service shall be of a compound certified to NSF/ANSI/CAN 61.
9.4.4 Elastomer seats shall conform to ASTM D2000 for the compound selected and shall be rated by the manufacturer for the service fluid and the maximum service temperature at the valve.
9.4.5 The orifice of air release valves and the small orifice of combination valves shall be of stainless steel or bronze, and shall be replaceable without removing the valve from the line.

9.5 Trim

9.5.1 Linkages, pivot pins, float guides, orifice buttons, and seat retainers shall be stainless steel, Type 304 or Type 316 conforming to ASTM A276 / A276M, and shall not be of plated carbon steel.
9.5.2 Trim in wastewater-pattern valves shall be Type 316 stainless steel.
9.5.3 Body and cover bolting shall be stainless steel conforming to ASTM F593, Alloy Group 1 for Type 304 and Alloy Group 2 for Type 316, and bolting on wastewater-pattern valves and on valves in vaults shall be Type 316.

10 End Connections

10.1 Inlet Connection

10.1.1 The inlet connection of valves 2 in. and smaller shall be as indicated in the datasheet.
Inlet Connection, Valves 2 in. and Smallerradio
● Threaded, NPT per ASME B1.20.1
○ Flanged
NOTE A threaded inlet screws onto the isolation valve and the tap, and it is how nearly every small air valve is furnished and installed. A flanged inlet in the small sizes is selected where the plant's standard is to flange every process valve, where the valve is stainless steel and the piping is flanged throughout, or where a threaded joint in a plastic chemical line would crack the fitting. (10.1.2)
10.1.3 Valves 3 in. and larger shall have flanged inlets.
10.1.4 Flanged inlets on 150 psi class valves shall be drilled to ASME B16.1 Class 125, and on 300 psi class and higher valves to ASME B16.1 Class 250, with ductile iron flanges conforming to ASME B16.42 Class 150 or Class 300 respectively.
10.1.5 Flanged inlets shall be flat faced, and a raised-face mating flange shall not be bolted to a cast iron flange.

10.2 Outlet Connection

10.2.1 The outlet of each valve shall be as indicated in the datasheet.
Outlet Connectionselect
Threaded outlet with a removable protective cowl and screen
Threaded outlet for a piped vent
Flanged outlet for a piped vent

11 Surge Suppression

11.1 Where the valve schedule designates slow closing or surge suppression for an air/vacuum or combination valve, the valve shall be furnished with a device of the type indicated in the datasheet.
Slow-Closing or Surge-Check Deviceradio
○ Integral slow-closing device that throttles the exhaust before the float seats
○ Separate surge-check unit mounted between the isolation valve and the air valve
NOTE A large orifice that exhausts freely lets the water column arrive at the valve at the velocity the pump drives it, and the float slams onto the seat against that column, which is the surge that cracks a cast iron body or lifts a vault lid. An integral slow-closing device throttles the exhaust as the air velocity rises so the column decelerates before it reaches the float, and it is part of the valve body. A separate surge-check unit is a disc beneath the valve that closes against a high exhaust velocity and leaves a small bypass open, so it protects any standard valve above it and is retrofitted to an existing one. The locations that need either are the ones where a column separates and rejoins, which is a hydraulic transient decision the valve schedule carries. (11.2)
11.3 A surge-check unit shall admit air freely in the inflow direction and shall not restrict the air admission capacity of the valve above it.
11.4 The manufacturer shall state in the submittal the exhaust velocity at which the device begins to throttle or close and shall confirm that the valve exhausts the filling rate stated for its location below that velocity.

12 Isolation Valve

12.1 Each air valve shall be furnished with a full-port isolation valve of the type indicated in the datasheet, installed between the pipeline outlet and the air valve inlet, so that the air valve can be removed with the line in service.
Isolation Valve Beneath Each Air Valveselect
Full-port ball valve, furnished by the air valve manufacturer
Resilient-seated gate valve
Eccentric plug valve
Butterfly valve
NOTE A ball valve is the isolation valve of a small air valve, furnished with it by the air valve manufacturer as a matched assembly, and it is a quarter turn to close in a vault where the operator is reaching down. A resilient-seated gate valve is the isolation valve of a large water-service valve, where a ball valve of the inlet size does not exist, and an eccentric plug valve is the isolation valve of a large wastewater-service valve, where solids would pack a gate valve's seat. A butterfly valve isolates a large valve at the lowest cost and intrudes its disc into the inlet, which costs air capacity at the small differentials this valve is sized to. The size of the air valve and its service decide this more than preference does, and the field is not defaulted because a project carries both small and large valves. (12.2)
12.3 A ball valve furnished as the isolation valve shall be of stainless steel or bronze with a stainless steel ball and stem, rated for the pressure class of the air valve, and certified to NSF/ANSI/CAN 61 in potable water service.
12.4 A gate, plug, or butterfly valve furnished as the isolation valve shall conform to Resilient Seated Gate ValvesResilient-Seated Gate ValvesResolves to the current adopted revision.sync/resilient-seated-gate-valves, Eccentric Plug ValvesEccentric Plug ValvesResolves to the current adopted revision.sync/eccentric-plug-valves, or Butterfly ValvesButterfly ValvesResolves to the current adopted revision.sync/butterfly-valves respectively, and shall be furnished under this standard with the air valve.
12.5 The isolation valve shall be of the same nominal size as the air valve inlet and shall be installed with its stem accessible from the vault hatch or the operating floor.

13 Coatings

13.1 Ferrous interior and exterior surfaces of each valve body and cover, except seating surfaces and machined flange faces, shall be coated at the factory in accordance with AWWA C550 with the system indicated in the datasheet.
Shop Coating System on Ferrous Surfacesselect
Fusion-bonded epoxy, AWWA C550
Two-part liquid epoxy, AWWA C550
Not applicable, stainless steel or reinforced nylon body
Manufacturer's standard (by default)
NOTE Fusion-bonded epoxy is applied as a powder to a heated casting and cures into a hard, holiday-free film that bonds to blast-cleaned iron better than any liquid coating, and it is applied only in a shop equipped to heat the casting. Two-part liquid epoxy to the same standard is applied by spray in any coating shop. Both meet AWWA C550, both are certified to NSF/ANSI/CAN 61 by the manufacturers that offer them, and the choice follows the manufacturer's process rather than the project. A stainless steel or reinforced nylon body is not coated. (13.2)
13.3 Shop coatings on valves in potable water service shall be certified to NSF/ANSI/CAN 61.
13.4 Shop coatings shall be applied over a surface prepared and to a dry film thickness in accordance with AWWA C550, and shall be holiday tested in accordance with that standard before shipment.
13.5 Coating on the interior of wastewater-pattern valves shall extend over every surface of the body and cover, including the surfaces above the liquid level that the sewage gas reaches.
13.6 Coating that is damaged in shipment or installation shall be repaired with the coating manufacturer's repair material in accordance with the coating manufacturer's written procedure, and a repair that cannot restore a holiday-free film shall be cause for rejection of the valve.
13.7 Where the plant's finish scheme requires a field-applied finish coat on exposed valves, the finish coat shall be furnished under High Performance CoatingsHigh-Performance CoatingsResolves to the current adopted revision.sync/high-performance-coatings over the shop epoxy, and the valve manufacturer shall state the surface preparation the finish coat requires over its epoxy.

14 Factory Testing

14.1 Each valve shall be hydrostatically shell tested at the factory in accordance with AWWA C512, at the pressure and for the duration that standard prescribes for its class, with no leakage through the body, the cover joint, or the accessory connections.
14.2 Each valve shall be seat tested at the factory with the body full and the float seated, at the rated working pressure and at the lowest pressure AWWA C512 prescribes, with no leakage past the seat.
14.3 Each air release valve and each combination valve shall be functionally tested at the factory by admitting air to the body under pressure and confirming that the small orifice opens and vents and then recloses drop-tight when the liquid returns.
NOTE The low-pressure seat test is the one that matters. A float that seals at 150 psi because the pressure drives it into the seat weeps at 5 psi, which is the pressure in a gravity-fed line or in a force main between pump cycles, and the valve dribbles onto the vault floor for the rest of its life. AWWA C512 tests the seat at both ends of the range for that reason. (14.4)
14.5 A valve that fails any factory test shall be corrected and retested, and the Contractor shall bear the cost of the correction and the retest.
14.6 Certified test reports identifying each valve by serial number shall be furnished for every valve before shipment, and witnessing of factory tests shall follow the policy selected under Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process.

15 Installation

15.1 Mounting at High Points

15.1.1 Each air valve shall be installed vertically, with its inlet plumb, on an outlet at the top of the pipe at the location shown on the piping profile, and shall not be installed on the side of the pipe or on a horizontal branch.
15.1.2 The outlet on the pipe shall be a tee, a welded or tapped outlet, or a tapping saddle furnished under the standard governing the piping, of a size not smaller than the air valve inlet, located at the crown of the pipe at the high point.
NOTE An air valve mounted on the side of a pipe sits below the crown where the air collects, and it vents nothing until the air pocket has grown to reach it; by then the pocket has taken a share of the flow area. A branch that runs horizontally from the crown holds a slug of water that the air has to pass through. The valve sits on top of the pipe, at the highest point, on a riser that rises continuously. (15.1.3)
15.1.4 The riser from the pipe outlet to the isolation valve shall rise continuously without a trap or a horizontal run, and shall be supported independently of the air valve.
15.1.5 Each valve shall be installed with clearance above it for the removal of the cover and the float, and the clearance shall be not less than the manufacturer's published removal clearance.
15.1.6 Where the valve inlet is threaded, the valve shall be made up with the wrench on the inlet boss and not on the body, and the joint shall be sealed with a thread sealant certified to NSF/ANSI/CAN 61 in potable water service.

15.2 Exposed Valves in Galleries and Buildings

15.2.2 The discharge piping from an air valve shall be of the same nominal size as the valve outlet, shall be routed without a trap, and shall not be connected to the vent of any other valve or to a pressurized drain.
15.2.4 Where an air valve in a building is in wastewater service, the vent from its outlet shall be piped to the exterior or to the building's odor control system as shown on the process mechanical plans, and shall not discharge into the room.

15.3 Valves on Buried Lines Within the Plant

15.3.1 Each air valve on a buried line within the plant shall be installed in an enclosure of the type indicated in the datasheet, except on a site sewage force main whose vault is furnished under Sanitary Sewer SystemsSanitary Sewer Systems (Site)Resolves to the current adopted revision.sync/sanitary-sewer-systems and on a site water main whose enclosure is furnished under the site standard.
Air Valve Enclosure on Buried Linesselect
Precast concrete vault with a hatch sized for valve removal
Fiberglass vault with a hatch sized for valve removal
Cast-in-place concrete vault with a hatch sized for valve removal
Above-grade insulated enclosure on a riser from the pipe
NOTE A precast concrete vault arrives as a unit, carries traffic loads with the right cover, and is the enclosure most plant yard lines use. A fiberglass vault is light enough to set by hand, does not corrode in a wastewater vault's atmosphere, and floats out of wet ground unless it is anchored. A cast-in-place vault fits an awkward location or a large valve and costs the formwork and the schedule. An above-grade enclosure puts the valve where an operator reaches it without a confined-space entry and where the vent is in the open air, at the price of an insulated and heated box above grade in a cold climate and a riser that is a traffic hazard in a yard. The enclosure follows the location, the climate, and the plant's confined-space practice rather than the valve, so none is defaulted. (15.3.2)
15.3.3 The vault shall have a hatch or cover sized for the removal of the air valve and its isolation valve through the opening without entering the vault where the vault is less than 4 ft deep, and sized for entry with a ladder where it is deeper.
15.3.4 The vault shall have a drain to daylight or to a storm structure where the grading permits, and where it does not, a sump with a gravel bottom sized to drain the volume of the vault.
15.3.5 The vault floor shall be set so that the air valve outlet is above the flood elevation shown on the site grading plan, and where that elevation cannot be cleared, the vent shall be extended above it and the vault shall be sealed against inflow at the hatch.
15.3.6 Vaults in vehicular areas shall carry covers rated for the traffic load the standard governing the site paving requires, and vaults shall be located outside vehicular areas where the profile permits.
15.3.7 Each buried air valve shall be located on the record drawings by not fewer than two tie dimensions to permanent surface features, with the depth from the hatch to the valve inlet.

15.4 Vent to Atmosphere

15.4.1 The outlet of each air valve in a vault shall be piped to atmosphere through a vent that rises from the valve outlet, passes through the vault wall or roof, and terminates above grade with the open end turned down and fitted with a corrosion-resistant insect screen.
15.4.2 The vent termination shall be above finished grade by not less than the height indicated in the datasheet.
Vent Termination Height Above Finished Graderange
in.
121824364860
NOTE A vent that terminates near grade is buried by the first snowfall, flooded by the first storm that ponds around the vault, and mowed off by the first crew that does not see it. Two or three feet clears the snow and the ponding of most sites; a taller vent is set where the snow depth or the flood elevation demands it, and a shorter one where the vault is inside a fenced yard that is kept clear. The height follows the site rather than the valve, so it is not defaulted. (15.4.3)
15.4.4 The vent pipe shall be of the same nominal size as the valve outlet, shall be of stainless steel or Schedule 80 PVC within the vault and of stainless steel or galvanized steel above grade, and shall be supported so that its weight is not carried by the air valve.
15.4.5 Vent terminations in wastewater service shall be located so that the discharge is not within 10 ft of a building air intake, a door, or an operable window, and shall be marked with the service.
NOTE The vent of a wastewater air valve is a sewer vent, and it discharges the sewage gas the valve releases on every cycle. It is kept away from intakes and doors for the same reason a building sewer vent is. (15.4.6)
15.4.7 The vent pipe shall not be connected to the vent of any other valve, to a manhole, or to a storm structure.

15.5 Freeze Protection

15.5.1 Where a vault floor, an above-grade enclosure, or an exposed valve is above Frost DepthFrost DepthParameterEach project supplies its own value.frost-depth and Site Ambient Temperature MinimumSite Ambient Temperature MinimumParameterEach project supplies its own value.site-ambient-temperature-minimum is below 32°F, the air valve, its isolation valve, and its riser shall be protected from freezing by the method indicated in the datasheet.
Freeze Protection Methodselect
Insulated vault lid and insulated vent, relying on the earth temperature of the vault
Electric heat tracing of the valve, isolation valve, and riser, with insulation
Thermostatically controlled enclosure heater with insulated enclosure
Not applicable, no valves above frost depth
15.5.3 Heat tracing and enclosure heaters shall be furnished under Electric Heat TracingElectric Heat TracingResolves to the current adopted revision.sync/electric-heat-tracing where that standard is on the project, and otherwise shall be self-regulating heat tracing or a thermostatically controlled heater rated for the enclosure, with a circuit shown on the electrical drawings.
15.5.4 The vent of an air valve with freeze protection shall be insulated from the valve outlet to the vault wall, and the vent termination above grade shall not be insulated or heated where doing so would close the screen.
NOTE An air valve holds water in its body between cycles, and that water freezes before the line does because the body is small and sits at the top of the vault where the cold air is. A frozen float does not lift, and the next draindown collapses the pipe the valve was there to protect. The protection covers the body, not the line. (15.5.5)

15.6 Field Testing

15.6.1 Each air valve shall be observed during the first filling of its line, and the Contractor shall record that the large orifice exhausted air and closed without discharging water beyond the outlet piping and that the small orifice vented the residual air after the line was full.
15.6.2 Each valve shall be observed for leakage past the seat and at the cover joint with the line at working pressure for not less than 30 minutes after the line is full, and a valve that leaks at the seat or weeps at the cover shall be corrected or replaced by the Contractor before the piping is tested.
15.6.3 Each wastewater-pattern valve shall be backflushed once through its accessories after the first filling, in the presence of the Owner's operations representative, and the procedure shall be recorded on the field test record.
15.6.4 The isolation valve beneath each air valve shall be closed and reopened once with the line under pressure, and the operation shall be recorded.
15.6.5 The field test shall be witnessed on the basis selected for field tests under Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process, and the Contractor shall give the witnessing party not less than five business days notice of the first filling of each line.
15.6.6 The Contractor shall bear the cost of correcting a valve that fails a field test and of the retest, including the cost of the witness's attendance at the retest.
15.6.7 The piping pressure test itself shall be performed under the standard governing the piping, with the air purged through the air valves before the test pressure is applied and with each air valve's isolation valve open during the test unless the valve is rated below the test pressure, in which case the isolation valve shall be closed and the valve shall be excluded from the test boundary.

16 Delivery, Storage, and Handling

16.1 Valves shall be shipped with the inlet and outlet openings covered, with the float secured against movement where the manufacturer provides a shipping restraint, and with the covers left in place until the valve is set on its riser.
16.2 Valves shall be stored off the ground, under cover, and out of direct sunlight, and reinforced nylon bodies and elastomer seats shall be stored away from ozone sources such as motors and welding equipment.
16.3 Valves shall be lifted by the body or by the lifting lugs the manufacturer provides, and shall not be lifted by the outlet, the vent connection, the accessories, or the isolation valve.
16.5 The Contractor shall bear the cost of repairing or replacing a valve damaged in delivery, storage, or handling.

17 Warranty

17.1 The Contractor shall warrant each air valve, its isolation valve, its accessories, and its surge device against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.
Air Valve Warranty Periodrange
years
1235
Default: Not less than 1 years
17.2 Where the contract General Conditions or Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process specify a longer warranty period than the datasheet, the longer period shall govern.
17.3 A valve that leaks past its seat at or below the rated working pressure, fails to exhaust or admit air at its rated capacity, or whose float, orifice, or accessory fails within the warranty period shall be repaired or replaced by the Contractor at no cost to the Owner.
17.4 The Contractor shall bear the cost of entering a vault or excavating to reach a valve for a warranted repair, of draining and refilling the piping the repair requires, and of repairing any other work damaged by the failure or by the repair.
17.5 A repaired or replaced valve shall carry a warranty running for a full new term from the date the repair is accepted, or for the remainder of the original term, whichever ends later.

18 Spare Parts

18.1 The Contractor shall furnish the spare parts indicated in the datasheet, packaged, labeled with the valve type and size they fit, and delivered to the Owner before substantial completion, on the spare parts basis selected under Common Work Results ProcessCommon Work Results for Process EquipmentResolves to the current adopted revision.sync/common-work-results-process.
Spare Parts Furnishedcheckbox
☑ One seat and orifice assembly for each air release valve size and each combination valve size
☐ One float for each valve size and pattern
☑ One cover gasket for each valve size
☐ One set of backflushing accessory valves for each wastewater-pattern valve size
☐ One vent screen for each vent termination size
18.2 Spare parts shall be the products of the valve manufacturer and shall be interchangeable with the parts installed in the valves furnished.
NOTE The seat and orifice assembly is the one wearing part every air valve has and the one a crew replaces in place, so a set per size is the spare that is used. A float is held where the valve is in wastewater service and a float that has filled with sewage is replaced rather than cleaned. A vent screen is the part that rusts off first and the one nobody stocks. (18.3)
18.4 The spare parts list, with the manufacturer's part numbers, shall be included in the operation and maintenance data.