Process Check Valves
Initial publication
Showing changes from Initial revision
to Rev 1
in Process Check Valves.
+---
+title: Process Check Valves
+category: Process / Valves
+description: >
+ When to use: Check valves individually specified on the pump discharges and process piping of water treatment plants, wastewater treatment plants, pump stations, and industrial process facilities, in raw, settled, finished, reclaimed, and plant water, wastewater, sludge, scum, grit, and industrial process service, exposed in galleries, buildings, and vaults or buried in yard piping. Covers swing check valves under AWWA C508 with their lever and weight, lever and spring, air cushion, and oil dashpot closure provisions; resilient-hinge rubber flapper check valves; tilting-disc check valves; ball check valves for sludge and grit; silent spring-loaded center-guided check valves under MSS SP-125 and nozzle check valves; dual-disc wafer check valves under AWWA C518 and API 594; foot valves for suction-lift pumps; rubber duckbill check valves at outfalls and overflows; the closure response the Engineer of Record's surge analysis requires of each pump discharge valve and the types that deliver it; body, disc, seat, and hinge materials; pressure rating and end connections; position indication and limit switches; the backflow actuator; AWWA C550 coatings; vault and buried installation; shop testing; installation orientation; and the field closure test on each pump.
+ Not intended for: Check valves furnished inside a packaged lift station (see [[sync/packaged-pump-stations]]), a building sewage ejector or sump package (see [[sync/sump-and-sewage-pumps]]), a domestic water booster package (see [[sync/domestic-water-booster-pumps]]), fire pump trim and fire service piping (see [[sync/fire-pumps]], [[sync/fire-protection-piping]], and [[sync/underground-fire-service-mains]]), building hydronic piping (see [[sync/hvac-piping-valves]]), or domestic water piping (see [[sync/plumbing-piping-valves]]); backflow prevention assemblies (see [[sync/backflow-prevention]]); pump control valves, surge anticipator valves, surge relief valves, and other pilot-operated automatic control valves, which are not yet owned by a SynC standard; modulating control valves (see [[sync/control-valves-and-actuators]]); the isolation valves beside the check valve (see [[sync/resilient-seated-gate-valves]], [[sync/butterfly-valves]], [[sync/eccentric-plug-valves]], and [[sync/knife-gate-valves]]) and their actuators (see [[sync/valve-and-gate-actuators]]); air release and vacuum valves on the pump discharge (see [[sync/air-release-and-vacuum-valves]]); thermoplastic check valves for chemical feed service, which are not yet owned by a SynC standard; the piping the valves sit in (see [[sync/ductile-iron-process-piping]], [[sync/steel-and-stainless-process-piping]], and [[sync/plastic-process-piping]] inside the plant fence, [[sync/water-distribution-piping]] and [[sync/site-utilities]] for buried site water mains, and [[sync/sanitary-sewer-systems]] for sewage force mains); the surge analysis itself, which is the Engineer of Record's; and the field-applied finish coat system over the shop coating (see [[sync/high-performance-coatings]]).
+---
+
+# Scope {toc}
+
+## This standard covers the check valve furnished as an individually specified product on a pump discharge or a process line in a water, wastewater, or industrial plant and its pump stations: the valve that lets the pump fill the line and holds the line's contents off the pump when the pump stops. {note}
+
+## The boundary of the work is the valve as a shop-assembled unit: the body and its end connections, the closure member and its seat, the hinge, shaft, or guide that carries the closure member, the lever, weight, spring, dashpot, or cushion that governs how it closes, the position indicator and limit switches where furnished, the shop coating, and the shop tests, together with the installation, the adjustment on the running pump, and the field closure test that prove it in the line. {note}
+
+## A check valve is the one valve in a pump station that operates itself, on every start and every stop, for the life of the station, and the one that destroys the station when it operates wrong. A disc that is still open when the column reverses is slammed shut by the reversing flow, and the pressure rise that follows the slam travels back down the main as a water hammer that lifts pumps off their bases and splits pipe. The type, the closure assist, and the cushioning of a pump discharge check valve are chosen against the deceleration of the column it holds, which is a property of the piping system and of the pump, and that is why this standard carries the closure response as a selection per valve and is prescriptive about adjustment on the running pump. {note}
+
+## AWWA C508 describes the swing check valve of waterworks service, 2 in. through 48 in., with a full waterway and an externally mounted lever, and AWWA C518 the dual-disc valve that closes under spring load between two flanges. MSS SP-125 describes the spring-loaded center-guided silent check of iron bodies, and API 594 the wafer, lug, and flanged check valves of industrial piping. The tilting-disc, ball, rubber flapper, foot, and duckbill valves have no consensus product standard of their own and are furnished to the manufacturer's published design, tested at the pressures of AWWA C508 or API 598 as this standard directs for each. {note}
+
+## This standard is read with [[sync/common-work-results-process]], which carries the submittal register, the factory and witnessed test policy, the manufacturer's field services, the data nameplate, the anchorage basis, and the warranty and spare parts administration for every process valve, and nothing here restates them. {note}
+
+## Check valves shall be of the types selected under this standard for the service of each valve and shall be rated for the working pressure indicated for that valve on the valve schedule.
+
+## Check valves in potable water service, from the raw water intake through the finished water storage, shall be certified to NSF/ANSI/CAN 61 and NSF/ANSI/CAN 372 for every wetted component, including the seat, the coating, and the lubricants.
+
+## A check valve is a product of the piping it sits in and of the pump it protects, and the standards that govern each stay where they are. The pump discharge check valve on a horizontal, vertical turbine, submersible, or positive displacement process pump is furnished under this standard; the isolation valve beside it, the air valve ahead of it, and the actuator on that isolation valve are furnished under their own standards. {note}
+
+## The following are outside this scope and are governed by the standards named. {note}
+- The pumps whose discharge these valves serve: [[sync/horizontal-centrifugal-process-pumps]], [[sync/vertical-turbine-pumps]], [[sync/submersible-solids-handling-pumps]], and [[sync/positive-displacement-pumps]]
+- The isolation valve on each pump discharge: [[sync/resilient-seated-gate-valves]], [[sync/butterfly-valves]], and [[sync/eccentric-plug-valves]]; the electric, pneumatic, and hydraulic actuators on those isolation valves: [[sync/valve-and-gate-actuators]]
+- Air release, air/vacuum, and combination air valves on the pump discharge and the force main: [[sync/air-release-and-vacuum-valves]]
+- Modulating control valves of every body style, with their actuators and positioners: [[sync/control-valves-and-actuators]]
+- Check and isolation valves furnished inside a packaged lift station: [[sync/packaged-pump-stations]]; inside a building sewage ejector, grinder, or sump package: [[sync/sump-and-sewage-pumps]]; inside a domestic water booster package: [[sync/domestic-water-booster-pumps]]
+- Check valves in building hydronic piping: [[sync/hvac-piping-valves]]; in domestic water piping: [[sync/plumbing-piping-valves]]; in fire pump trim and fire service piping: [[sync/fire-pumps]], [[sync/fire-protection-piping]], and [[sync/underground-fire-service-mains]]
+- Backflow prevention assemblies at cross-connections: [[sync/backflow-prevention]]
+- The process piping, its flange bolting and gaskets, its supports, and its pressure test: [[sync/ductile-iron-process-piping]], [[sync/steel-and-stainless-process-piping]], and [[sync/plastic-process-piping]]
+- Buried site water mains and the vaults and valve boxes on them: [[sync/water-distribution-piping]] and [[sync/site-utilities]]; sewage force mains beyond a station: [[sync/sanitary-sewer-systems]]
+- Field-applied finish coat systems: [[sync/high-performance-coatings]]; valve tags and piping identification: [[sync/mechanical-identification]]; limit switch wiring and the supervisory points: [[sync/control-systems-integration]]
+
+## Pump control valves, surge anticipator valves, surge relief valves, and the other pilot-operated automatic control valves of a pump station, and thermoplastic ball, diaphragm, and check valves for chemical feed service, are not yet owned by a SynC standard. {note}
+
+## A check valve on a buried site water main or on a sewage force main outside the station is furnished under the standard governing that main, which specifies it with the main, unless the valve schedule designates it as furnished under this standard. {note}
+
+# Referenced Standards {toc}
+
+## Valves, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## 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 C508 | Swing-Check Valves for Waterworks Service, 2 In. Through 48 In. |
+| AWWA C518 | Dual-Disc Swing-Check Valves for Waterworks Service |
+| AWWA C550 | Protective Interior Coatings for Valves and Hydrants |
+| AWWA C105 / A21.5 | Polyethylene Encasement for Ductile-Iron Pipe Systems |
+| AWWA C111 / A21.11 | Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings |
+| AWWA C606 | Grooved and Shouldered Joints |
+| 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 |
+| ASME B16.10 | Face-to-Face and End-to-End Dimensions of Valves |
+| ASME B16.42 | Ductile Iron Pipe Flanges and Flanged Fittings: Classes 150 and 300 |
+| MSS SP-25 | Standard Marking System for Valves, Fittings, Flanges, and Unions |
+| MSS SP-71 | Gray Iron Swing Check Valves, Flanged and Threaded Ends |
+| MSS SP-125 | Gray Iron and Ductile Iron In-Line, Spring-Loaded, Center-Guided Check Valves |
+| MSS SP-136 | Ductile Iron Swing Check Valves |
+| API 594 | Check Valves: Flanged, Lug, Wafer, and Butt-Welding |
+| API 598 | Valve Inspection and Testing |
+| ASTM A126 | Gray Iron Castings for Valves, Flanges, and Pipe Fittings |
+| ASTM A276 / A276M | Stainless Steel Bars and Shapes |
+| ASTM A307 | Carbon Steel Bolts, Studs, and Threaded Rod 60 000 PSI Tensile Strength |
+| ASTM A536 | Ductile Iron Castings |
+| ASTM A743 / A743M | Castings, Iron-Chromium, Iron-Chromium-Nickel, Corrosion Resistant, for General Application |
+| ASTM B62 | Composition Bronze or Ounce Metal Castings |
+| ASTM B148 | Aluminum-Bronze Sand Castings |
+| ASTM D2000 | Classification System for Rubber Products in Automotive Applications |
+| ASTM D2240 | Rubber Property: Durometer Hardness |
+| ASTM F593 | Stainless Steel Bolts, Hex Cap Screws, and Studs |
+| NSF/ANSI/CAN 61 | Drinking Water System Components: Health Effects |
+| NSF/ANSI/CAN 372 | Drinking Water System Components: Lead Content |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following for the Engineer of Record's review and return before any check valve is released for manufacture:
+
+- Product data for each valve size, type, pressure rating, and service, identifying the design standard, the body, closure member, seat, hinge pin or shaft, spring, and bearing materials with their ASTM designations, the laying length, and the published head loss curve
+- Dimensioned drawings for each valve showing the end connections and flange drilling, the cover and the clearance to remove it and withdraw the closure member, the lever, weight, spring, dashpot, or cushion and its swing envelope, the position indicator, and the limit switch housing and conduit entry where furnished
+- Closure data for each pump discharge valve, stating the type and closure assist proposed, the deceleration of the discharge column used, and the manufacturer's statement that the valve furnished delivers the closure response designated for that valve
+- Elastomer compound data for each seat, flapper, ball cover, and duckbill, stating the compound, the durometer hardness per ASTM D2240, and the service fluid and temperature range the manufacturer rates it for
+- Coating system 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
+- Limit switch and position transmitter data where furnished, with the contact rating, the enclosure type, and the wiring diagram
+- Vault access and support details for each buried valve, with the encasement where the valve is direct-buried
+- A field closure test plan identifying the pump stop conditions to be demonstrated, the adjustment procedure, the observation points, and the record form
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Valve product data by size, type, rating, and service"
+ - "Dimensioned valve drawings with cover and lever clearances"
+ - "Closure data and closure response statement for pump discharge valves"
+ - "Elastomer compound data"
+ - "Coating system product data"
+ - "Limit switch and position transmitter data"
+ - "Vault access and buried valve details"
+ - "Field closure test plan"
+default:
+ - "Valve product data by size, type, rating, and service"
+ - "Dimensioned valve drawings with cover and lever clearances"
+ - "Closure data and closure response statement for pump discharge valves"
+ - "Elastomer compound data"
+ - "Coating system product data"
+ - "Field closure test plan"
+constraint: all_of
+```
+
+### Manufacture of a valve shall not begin until the submittal covering that valve has been returned by the Engineer of Record.
+
+### The closure data is the submittal that catches the error on this product. A swing check that is right in every material and rating still slams on a short, steep force main, and the manufacturer that has the deceleration in hand is the only party able to say before shipment whether its lever and weight, its spring, or its dashpot will close the disc in time. {note}
+
+## Closeout Submittals {toc}
+
+### The Contractor shall submit the following at substantial completion, before the check valves are accepted:
+
+- Certified factory test reports for every valve, identified by serial number, recording the shell test and the seat test with their pressures, durations, and results
+- Signed and dated field closure test records for every pump discharge valve, recording each pump stop condition demonstrated, the final lever, weight, spring, or dashpot setting, and the observation of closure
+- Record drawings locating every buried valve by tie dimensions to permanent surface features, with its type, its orientation, and the vault or encasement furnished
+- Operation and maintenance data for each valve type and size, including seat, flapper, ball, and spring replacement, lever and weight adjustment, dashpot filling and setting, and limit switch adjustment
+- Coating inspection records for shop coatings, recording the dry film thickness and the holiday test result for each valve
+- Warranty documentation
+
+```datasheet
+label: Closeout Submittals Required
+type: checkbox
+options:
+ - "Certified factory test reports by serial number"
+ - "Field closure test records with final settings"
+ - "Record drawings with buried valve ties and orientation"
+ - "Operation and maintenance data"
+ - "Shop coating inspection records"
+ - "Warranty documentation"
+default:
+ - "Certified factory test reports by serial number"
+ - "Field closure test records with final settings"
+ - "Record drawings with buried valve ties and orientation"
+ - "Operation and maintenance data"
+ - "Warranty documentation"
+constraint: all_of
+```
+
+# Quality Assurance {toc}
+
+## Manufacturer Qualifications {toc}
+
+### Check valves of each type shall be the product of a manufacturer that has produced check valves of that type, in the sizes furnished, for water or wastewater service in North America for not less than five years.
+
+### The manufacturer shall furnish, on request, a list of not fewer than five installations of valves of the same type, size range, and rating that have been in service for not less than five years.
+
+### Where the parties disagree whether a listed installation is of the same type, size range, and rating, the Engineer of Record shall make the initial determination.
+
+### Replacement seats, flappers, balls, springs, hinge pins, shaft seals, and dashpot parts shall be available from the manufacturer for not less than fifteen years after shipment.
+
+## Single-Source Responsibility {toc}
+
+### Check valves of each type furnished under this standard shall be the product of a single manufacturer.
+
+### Each valve, its lever, weight, spring, dashpot, or cushion, and its position indicator and limit switches shall be furnished, assembled, and tested by the valve manufacturer as a unit, and the lever and weight or spring shall be set at the factory to the manufacturer's initial setting for the valve's closure response.
+
+### A valve shipped bare and fitted with a lever and weight in the field arrives with nobody responsible for the weight position, and the weight position is the one adjustment that decides whether the valve slams. The valve manufacturer is the party that knows its own disc mass and seat angle, so the initial setting is made where that is known and refined on the running pump. {note}
+
+## Marking {toc}
+
+### Each valve shall carry the markings the governing design standard requires, cast on the body or on a permanently attached corrosion-resistant nameplate, including the manufacturer, the size, the rated working pressure, the design standard, the body material, and the year of manufacture.
+
+### Valve markings shall conform to MSS SP-25.
+
+### The direction of flow shall be cast on the body of every valve as an arrow visible with the valve installed.
+
+# Service Conditions {toc}
+
+## Valve Schedule {toc}
+
+### The size, service fluid, service temperature, location, exposed or buried installation, and the installation orientation of each check valve shall be as indicated on [[drawing: the valve schedule]].
+
+### Each check valve on the project is either a pump discharge valve, installed between a pump and its isolation valve, or a process line valve, installed in a line to keep it from draining back or from being fed from the wrong direction, and the valve schedule names which each is. {note}
+
+### Size and rating are properties of each location on a project, and a standard that asserts either has decided the hydraulics. The valve schedule carries them per tag, and this standard carries what every valve of a given type has in common. {note}
+
+## Closure Response at Pump Stop {toc}
+
+### Each pump discharge check valve shall deliver the closure response indicated in the datasheet when the pump it serves stops.
+
+```datasheet
+label: Closure Response of Pump Discharge Check Valves
+type: select
+drawing_ref: "the valve schedule"
+options:
+ - "Unassisted closure under reverse flow"
+ - "Assisted closure beginning as forward flow decays"
+ - "Assisted closure with cushioned final travel"
+ - "Closure complete before reverse flow develops"
+ - "Controlled closure timed over the final travel against reverse flow"
+default: deferred
+```
+
+### The deceleration of the discharge column at pump stop, on which the closure response of each pump discharge valve is based, shall be as indicated on [[drawing: the pump discharge surge analysis summary on the valve schedule]].
+
+### The closure response is the Engineer of Record's answer to a hydraulic question this standard does not ask: how fast the column in the discharge piping decelerates when the pump stops, which depends on the static head, the length and profile of the main, the pump's inertia, and whether the stop is a normal one or a power failure. On a low-head, long, flat main the column coasts for seconds and an unassisted disc drops closed before anything reverses. On a high-head or short, steep main the column reverses in a fraction of a second, and the disc has to be already closing as the forward flow decays, by a weight or a spring, or already closed, by a spring strong enough to shut it before the reversal, or closed softly against the reverse flow by a cushion that takes the last part of the travel slowly. Where the surge analysis finds that a fast closure itself produces an unacceptable pressure rise, the last response, a timed closure that lets a controlled reverse flow pass while the disc completes its travel, is what the analysis asks for, and only a dashpot-controlled swing or tilting-disc valve delivers it. The response differs per pump group on most plants, which is why it is read from the valve schedule rather than defaulted. {note}
+
+### The manufacturer shall confirm in the closure data submitted, from the deceleration stated for each pump discharge valve, that the valve furnished delivers the designated closure response, and a valve the manufacturer cannot so confirm shall not be furnished for that location.
+
+### The type, the closure assist, and the cushioning furnished for each pump discharge valve shall be those selected under this standard, except where a different selection is designated for a particular valve on the valve schedule to deliver its closure response.
+
+## Exposed and Buried Service {toc}
+
+### Valves in exposed service are those installed in a building, a gallery, a vault, or above grade, where the cover, the lever, and the switches are reachable by hand; valves in buried service are those installed in a trench and backfilled. A check valve has no operator, so a buried check valve has no valve box and no extension stem, and whatever is bolted to its outside is out of reach until the valve is dug up. {note}
+
+### Each valve shall be furnished for exposed or buried service as indicated for its location on the valve schedule.
+
+### Levers, weights, springs, dashpots, and limit switches on valves installed outdoors or in unheated structures shall be rated by their manufacturers for continuous service at [[parameter: site-ambient-temperature-minimum]] and at [[parameter: site-ambient-temperature-maximum]], and dashpot fluid shall be of a grade that holds its setting across that range.
+
+### Levers, weights, springs, dashpots, limit switches, and shaft seals on valves in vaults whose floor is below [[parameter: seasonal-high-groundwater-elevation]], and on valves in wet wells, shall be sealed for continuous submergence.
+
+### A dashpot filled with an oil chosen for a heated gallery thickens in a January vault and closes the valve a second late, which is the slam the dashpot was bought to prevent. A vault below the water table floods, and a limit switch sealed for rain fills with water on the first flood and reports the valve closed from then on. The temperature range and the groundwater elevation are project facts, and the ratings follow them. {note}
+
+### Every elastomer, bearing, and seal in each valve shall be rated by its manufacturer for continuous service at the service temperature indicated for the valve on the valve schedule.
+
+# Check Valve Type by Service {toc}
+
+## Water Service {toc}
+
+### Check valves in raw, settled, finished, reclaimed, plant, and industrial process water service shall be of the type indicated in the datasheet, except where a different type is designated for a particular valve on the valve schedule.
+
+```datasheet
+label: Check Valve Type, Water Service
+type: select
+options:
+ - "Swing check, AWWA C508"
+ - "Tilting-disc check"
+ - "Silent spring-loaded center-guided check, MSS SP-125"
+ - "Nozzle check"
+ - "Dual-disc wafer check, AWWA C518"
+ - "Dual-disc wafer check, API 594"
+ - "Resilient-hinge rubber flapper check"
+```
+
+### A swing check gives the full waterway and the lowest head loss of the metal-disc valves, is serviced through its cover without removing it from the line, and carries the lever that lets the closure be assisted, cushioned, indicated, and switched; its disc has the longest travel of the group and is the one that slams where the column reverses quickly. A tilting-disc valve pivots its disc on trunnions just above center so the disc travels a short arc and closes in a fraction of a swing check's time, at a higher head loss and at a price several times the swing check's, and it is the valve of high-head, large pumps where a swing check cannot be made to close in time. A silent check closes its spring-loaded disc as the forward flow decays and is shut before the column reverses, with no lever, no indication, and no cushioning, at the highest head loss of the group, and it is the valve of booster stations and of plant water lines where the pressure rise of a fast closure is tolerable and the outside of the valve is nobody's concern. A nozzle check is a silent check built around a venturi body, so its disc is short-travel and its head loss is the lowest of the spring-closed valves, at a price above the tilting disc, and it is selected on large high-service pumps where both the slam and the head loss matter. A dual-disc wafer valve closes two spring-loaded half discs between two flanges in the shortest laying length and at the lowest weight and cost, serves a process line well, and is sized for a pump discharge only where the surge analysis has accepted its closure. A rubber flapper valve closes a steel-reinforced elastomer disc on a flex hinge through a short travel at a 45° seat, with no metal hinge pin to wear and the lowest cost of a serviceable body, and it is limited in pressure and in the sizes made. No type is the norm across the water services this standard covers, so none is defaulted. {note}
+
+## Wastewater and Scum Service {toc}
+
+### Check valves in raw and settled wastewater, return and waste activated sludge, scum, and other solids-bearing liquid service that passes a centrifugal pump shall be of the type indicated in the datasheet, except where a different type is designated for a particular valve on the valve schedule.
+
+```datasheet
+label: Check Valve Type, Wastewater and Scum Service
+type: select
+options:
+ - "Swing check, AWWA C508"
+ - "Resilient-hinge rubber flapper check"
+ - "Ball check"
+ - "Tilting-disc check"
+default: "Swing check, AWWA C508"
+```
+
+### A swing check with a full waterway passes the solids the pump passes, holds its disc clear of the flow when open, carries the lever and weight that the raw sewage pump discharge is almost always furnished with, and shows the plant from across the gallery whether the pump is moving water, which is why it is the valve on nearly every wastewater pump discharge and the default here. A rubber flapper valve seals on a rag or a stone that would hold a metal disc off its seat, is the quietest of the group, and is chosen on smaller stations and on scum lines where the fluid is the problem rather than the surge. A ball check has no hinge or seat to foul, clears itself of solids on every cycle, is the valve of grinder and small sewage pumps, and does not indicate its position or accept a lever or a switch. A tilting disc is selected on large raw sewage pumps on high-head force mains where the swing check cannot be made to close in time, at the cost of a seat that solids reach. {note}
+
+## Sludge, Grit, and Positive Displacement Pump Service {toc}
+
+### Check valves in thickened and digested sludge, grit slurry, and other heavy solids service, and on the discharge of positive displacement pumps in any service, shall be of the type indicated in the datasheet, except where a different type is designated for a particular valve on the valve schedule.
+
+```datasheet
+label: Check Valve Type, Sludge, Grit, and Positive Displacement Pump Service
+type: select
+options:
+ - "Ball check"
+ - "Swing check, AWWA C508"
+ - "Resilient-hinge rubber flapper check"
+ - "No check valve, pump stops against a closed discharge"
+```
+
+### A ball check is the valve of thick sludge and grit, because the ball rolls off its seat on every stroke and nothing in the body offers a ledge for solids to pack onto, and because a positive displacement pump's pulsing flow lifts and reseats a ball cleanly where it hammers a hinged disc on every stroke. A swing check serves thin sludge and the discharge of a rotary lobe or progressing cavity pump whose flow is nearly steady, with the lever and weight to damp the pulsation, and it needs its cover opened wherever grit packs under the disc. A rubber flapper valve seals on grit and on the stringy solids of a scum line and is chosen where the pressure and the size are within its range. A positive displacement pump cannot run against a closed discharge without its relief, and some plants omit the check valve on a sludge pump whose discharge is isolated by a plug valve and protected by a relief, because the check is the one component in the line that fouls; where the line can drain back through the pump or a second pump discharges into the same header, the check valve is not optional. No type is the norm across these services, so none is defaulted. {note}
+
+# Pressure Rating and End Connections {toc}
+
+## Rated Working Pressure {toc}
+
+### Each check valve shall carry a rated working pressure not less than the value indicated in the datasheet.
+
+```datasheet
+label: Rated Working Pressure
+type: range
+unit: psi
+drawing_ref: "the valve schedule"
+options:
+ min: 150
+ max: 300
+ setpoints: [150, 175, 200, 250, 300]
+default: deferred
+constraint: min
+```
+
+### Each valve shall carry a rated working pressure not less than the design working pressure, including the surge allowance, of the piping it is installed in under the standard governing that piping.
+
+### Each valve shall hold the full rated working pressure applied to the downstream face of the closed closure member, with the upstream side at atmospheric pressure, without leakage past the seat beyond the limit the governing design standard allows.
+
+### The rating that matters for a check valve is the reverse one. The valve is open under forward pressure and has nothing to hold; it is closed, with the static head of the main and the surge on its downstream face and an open pump on the other, when it is working, and that is the condition the seat test applies. AWWA C508 rates its swing checks by size at the working pressure the standard states, and manufacturers offer heavier bodies above it for high-head discharges, which is why the rating is read from the valve schedule rather than fixed here. {note}
+
+## Flange Drilling {toc}
+
+### Flanged valves shall be drilled to the template indicated in the datasheet.
+
+```datasheet
+label: Flange Drilling
+type: radio
+options:
+ - "ASME B16.1 Class 125"
+ - "ASME B16.1 Class 250"
+default: "ASME B16.1 Class 125"
+```
+
+### Flanges on ductile iron bodies drilled to the Class 125 template shall conform to ASME B16.42 Class 150, and flanges drilled to the Class 250 template shall conform to ASME B16.42 Class 300.
+
+### Flanges on steel and stainless steel bodies shall conform to ASME B16.5 Class 150 for Class 125 drilling and Class 300 for Class 250 drilling.
+
+### Class 125 drilling matches the flanges of every ductile iron fitting and flanged pipe in a plant and every iron valve beside it, and it is what the valve is bolted to on nearly every project. Class 250 drilling is selected where the connected piping is Class 250 or Class 300 for a pressure above the Class 125 rating, and the heavier flange needs the heavier body behind it. {note}
+
+### Flanged iron valves shall be flat faced, and laying lengths shall conform to the governing design standard for the type, and to ASME B16.10 for valves manufactured to MSS SP-71, MSS SP-125, MSS SP-136, or API 594.
+
+## End Connections {toc}
+
+### The end connection of each valve shall be as indicated in the datasheet.
+
+```datasheet
+label: End Connection
+type: select
+drawing_ref: "the valve schedule"
+options:
+ - "Flanged"
+ - "Mechanical joint"
+ - "Grooved end"
+ - "Wafer, between flanges"
+ - "Lug, tapped for flange bolting"
+ - "Threaded"
+default: deferred
+```
+
+### Flanged ends are the connection of exposed plant piping, where the valve is bolted between flanges it is unbolted from for service, and they are offered on every type and in every size. Mechanical joint ends take the gasket and gland of a buried ductile iron main and are the ends of a direct-buried swing or flapper valve. Grooved ends suit a grooved process piping system in the sizes the coupling manufacturer rates for the line pressure. A wafer body is clamped between two flanges by through-bolts, is the body of the dual-disc and most silent checks, and cannot hold pressure with either flange unbolted; a lug body bolts to each flange by tapped lugs and serves a dead end the wafer body cannot. Threaded ends are offered on small swing, silent, and ball checks and suit a threaded sludge, drain, or seal water line. The connection follows the piping at each location rather than the valve, which is why it is read from the valve schedule. {note}
+
+### Mechanical joint ends shall conform to AWWA C111 / A21.11, and the glands, gaskets, and bolts shall be furnished with the valve.
+
+### Grooved ends shall conform to AWWA C606, cut or rolled to the coupling manufacturer's groove dimensions for the body material.
+
+### Wafer-body valves shall be installed only between two flanges that remain permanently bolted, and shall not be installed at a dead end, at a blind flange, or at an equipment connection that is removed for service.
+
+### Threaded ends shall be furnished only on valves 3 in. and smaller.
+
+# Swing Check Valves {toc}
+
+## Swing Check Design Basis {toc}
+
+### Requirements in this section apply to every swing check valve furnished under this standard, whether selected in the datasheet for a service or designated for a particular valve on the valve schedule. {note}
+
+### Swing check valves 2 in. and larger in water and wastewater service shall conform to AWWA C508, and swing check valves in industrial process service may conform instead to MSS SP-71 or MSS SP-136 where the valve schedule designates the industrial standard.
+
+### Swing check valves shall have a full waterway, with the disc swinging clear of the flow path when fully open so that the net flow area through the open valve is not less than the area of a pipe of the valve's nominal size.
+
+### AWWA C508 is the standard every water and wastewater utility buys its swing checks against, and it requires the full waterway, the external lever, and the shell and seat tests the rest of this section relies on. MSS SP-71 and MSS SP-136 describe the gray and ductile iron swing checks of industrial piping, which are shorter, available threaded in the small sizes, and rated by cold-working pressure rather than by the AWWA size rating, and they serve the plant's industrial and seal water lines where the AWWA valve is longer than the piping has room for. {note}
+
+## Swing Check Body and Disc {toc}
+
+### The body and cover material of swing check valves shall be as indicated in the datasheet.
+
+```datasheet
+label: Swing Check Body Material
+type: select
+options:
+ - "Ductile iron, ASTM A536"
+ - "Gray cast iron, ASTM A126 Class B"
+ - "Stainless steel, ASTM A743 Grade CF8M"
+ - "Bronze, ASTM B62"
+```
+
+### Ductile iron carries the same pressure rating as gray iron at a lighter section and survives the bolting stress and the impact that crack a gray iron body, and it is the body of the heavier-rated valves and of nearly every valve made for buried or force main service. Gray iron is the body AWWA C508 was written around, is the lower-cost casting, and remains the body many utilities stock and specify for the plant gallery where nothing strikes it. A stainless steel body is selected where the fluid attacks coated iron, as in seawater, brine, or a chemical solution, and it removes the coating as a maintenance item at several times the cost. A bronze body is offered in the small sizes only and is the body of a threaded seal water or sample line valve. Neither iron is the norm across manufacturers and sizes, so no body is defaulted. {note}
+
+### The body shall have a bolted cover through which the disc, the hinge, the hinge pin, and the seat ring are removed and replaced without removing the body from the line.
+
+### The disc shall be of ductile iron, gray cast iron, bronze, or stainless steel, as the manufacturer's design for the body material provides, and shall be free to rotate on its hinge arm so that it seats on a different line on each closure.
+
+### The disc shall be hung on a hinge arm carried by a hinge pin that turns in bushings of bronze or stainless steel, and where the pin extends through the body to an outside lever it shall be sealed with a stuffing box or O-ring seals replaceable without removing the cover.
+
+### The seat ring shall be renewable, retained in the body by a method the manufacturer rates for the rated working pressure, and shall not be a seat machined into the body casting.
+
+### A disc that cannot turn on its arm seats on the same line every time, and the groove it wears there is the leak the valve develops in its fifth year. A seat ring that is part of the casting is replaced by replacing the valve. {note}
+
+## Swing Check Seat {toc}
+
+### The seat of swing check valves shall be as indicated in the datasheet.
+
+```datasheet
+label: Swing Check Seat Type
+type: radio
+options:
+ - "Resilient seat, elastomer on the disc or in the body seat ring"
+ - "Metal-to-metal seat, bronze or stainless steel disc ring on a matching seat ring"
+default: "Resilient seat, elastomer on the disc or in the body seat ring"
+```
+
+### Where a resilient seat is selected, the seat elastomer shall be as indicated in the datasheet.
+
+```datasheet
+label: Swing Check Seat Elastomer
+type: select
+options:
+ - "Nitrile (Buna-N)"
+ - "EPDM"
+ - "Neoprene"
+ - "Natural rubber"
+ - "Fluoroelastomer"
+```
+
+### A resilient seat seals drop-tight on a disc that has landed slightly off its line and on a particle a metal seat would hold open, which is why it is the seat of nearly every swing check in water and wastewater service and the default here; it is the one part of the valve that wears, and it is replaced from the cover. A metal-to-metal seat has nothing to replace and tolerates a temperature and a fluid no elastomer serves, at the cost of a seal that weeps on any imperfection, and it is selected on hot or chemical industrial lines and by utilities that have standardized on it. Among the elastomers, nitrile resists oils, grease, and hydrocarbons and swells in chloraminated water over years, which makes it the usual seat in wastewater, sludge, and raw water and a poor one downstream of chloramination. EPDM resists chlorine, chloramine, and ozone and is attacked by petroleum oils, which makes it the usual seat in treated and potable water and a poor one in raw sewage. Neoprene sits between the two on oil resistance and is specified where a utility's stock is neoprene. Natural rubber has the greatest abrasion resistance of the group and is selected for grit-laden water at the cost of ozone and oil resistance. Fluoroelastomer resists chemicals that attack all four and is selected for chemical and hot industrial service at several times the cost. No compound is the norm across the services this standard covers, so none is defaulted. {note}
+
+### The seat compound shall be rated by its manufacturer for the service fluid and the service temperature indicated for the valve on the valve schedule, and shall conform to ASTM D2000 for the compound selected.
+
+### Seats in potable water service shall be of a compound certified to NSF/ANSI/CAN 61.
+
+### Seat hardness shall be within the range the valve manufacturer publishes for the compound when tested in accordance with ASTM D2240, and the durometer value shall be stated on the elastomer compound data submitted.
+
+## Hinge Pin and Shaft {toc}
+
+### The hinge pin, and the shaft where the hinge pin extends through the body to an outside lever, shall be of the material indicated in the datasheet.
+
+```datasheet
+label: Swing Check Hinge Pin and Shaft Material
+type: select
+options:
+ - "Type 304 stainless steel, ASTM A276"
+ - "Type 316 stainless steel, ASTM A276"
+ - "Nickel-copper alloy"
+```
+
+### The hinge pin is the one part of a swing check that moves on every cycle and sits wetted between cycles, and the one that seizes where it corrodes. Type 304 serves treated water where chlorides are low and is the AWWA C508 baseline. Type 316 resists chloride pitting in wastewater, in chloraminated water, and in a vault that floods, at a small premium, and is what most wastewater specifications call for. A nickel-copper alloy resists seawater and brine where both stainless grades pit. No grade is the norm across the services this standard covers. {note}
+
+### Hinge pin bushings shall be of bronze or stainless steel, galvanically compatible with the pin in the service fluid, and shall be replaceable through the cover.
+
+## Outside Lever {toc}
+
+### Swing check valves shall be furnished with the outside lever provision indicated in the datasheet, except where a different provision is designated for a particular valve on the valve schedule to deliver its closure response.
+
+```datasheet
+label: Swing Check Outside Lever
+type: select
+options:
+ - "None, free-swinging disc"
+ - "Outside lever and adjustable weight"
+ - "Outside lever and adjustable spring"
+```
+
+### A free-swinging disc closes under its own weight and the reversing flow, has nothing outside the body to seal, adjust, or be struck, and is the swing check of a process line and of a low-head pump on a long main, where the column reverses slowly. A lever and weight starts the disc closing as the forward flow decays, so the disc is near its seat when the column reverses, shows the disc position to anyone in the gallery, gives the limit switch something to trip, and is the provision on nearly every wastewater and raw water pump discharge; the weight's position on the lever is the adjustment that tunes the closure to the pump, and a weight set too far out holds the disc partly closed against the running pump and costs head. A lever and spring does the same work in less room, closes faster than a weight on the same disc because the spring force does not fall off as the disc rises, and is the provision on short, high-head mains where a weight cannot close the disc in time; its closing force is not visible the way a weight's is, and it is adjusted with a tool. The provision follows the closure response of each pump discharge, which is why none is defaulted across a project. {note}
+
+### Outside levers shall be mounted on the hinge pin shaft outside the body, with the weight or the spring adjustable over the full range the manufacturer publishes for the valve size without disassembly, and with the lever arm marked at the position of the initial factory setting.
+
+### The outside lever shall be stopped so that the disc cannot travel past the fully open position and strike the cover, and the stop shall carry the force of the lever and weight without transmitting it to the disc.
+
+### Outside levers and weights shall be mounted on the side of the body indicated on [[drawing: the piping plans and sections]] so that the lever swings clear of adjacent piping, walls, and walkways through its full travel.
+
+## Closure Cushioning {toc}
+
+### Swing check valves shall be furnished with the closure cushioning indicated in the datasheet, except where a different cushioning is designated for a particular valve on the valve schedule to deliver its closure response.
+
+```datasheet
+label: Swing Check Closure Cushioning
+type: select
+options:
+ - "None"
+ - "Air cushion chamber on the outside lever"
+ - "Oil-filled dashpot on the outside lever"
+ - "Bottom-mounted buffer cushioning the final travel of the disc"
+default: "None"
+```
+
+### Most swing checks need no cushioning, because the lever and weight or spring closes the disc before the reversal or the reversal is slow enough that a free disc lands softly, and that is why none is the default. Where the surge analysis finds that the disc is still open when the column reverses and that the slam is unacceptable, a cushion takes the last part of the travel slowly. An air cushion is a piston in a vented cylinder on the lever that resists the closing travel through a bleed orifice; it is the simplest and cheapest cushion, holds no fluid to leak, and its setting drifts with temperature and with the wear of the piston. An oil dashpot is the same piston in a sealed oil-filled cylinder with an adjustable orifice; it holds its setting across years and temperatures, lets the closing time be set on the running pump, and is the cushion of the large high-head pump discharge, at a cost that includes the oil and its seals. A bottom-mounted buffer is a piston in the body below the disc that the disc strikes over the last few degrees of its travel, cushioning the seat contact without touching the lever; it is fitted where the lever is spring-loaded for a fast close and the seat impact itself is the problem, and where the lever cannot carry a cylinder in the space available. Each cushion lets the valve close most of its travel freely and controls only the end, so a cushioned valve is still a closing valve and not a slow one. {note}
+
+### Where an oil dashpot is furnished, it shall be fitted with an adjustable orifice setting the closing time over the cushioned travel, a sight gauge or dipstick, and a fill port reachable with the valve installed, and the oil shall be of the grade the manufacturer publishes for the service temperature range.
+
+### Where an air cushion chamber or an oil dashpot is furnished, the cushioned portion of the disc travel shall be adjustable and shall not exceed the portion the manufacturer publishes for the valve size, so that the disc closes freely through the remainder of its travel.
+
+### Where the closure response designated for a valve is a controlled closure timed over the final travel against reverse flow, the dashpot shall be a two-stage dashpot that closes the disc freely to the position the manufacturer publishes and then at the closing time set under this standard through the remainder of the travel, and the closing time shall be adjustable over the range the surge analysis states for that valve.
+
+## Backflow Actuator {toc}
+
+### Swing check valves shall be furnished with the backflow actuator provision indicated in the datasheet.
+
+```datasheet
+label: Swing Check Backflow Actuator
+type: radio
+options:
+ - "Not furnished"
+ - "Manual backflow actuator holding the disc open"
+default: "Not furnished"
+```
+
+### A backflow actuator is a screw or a lever on the cover or the hinge shaft that holds the disc off its seat by hand, so that the force main drains back through the pump to the wet well to flush the pump or to drain the main for work on it, and it is bought on a sewage pump station whose plant has no other way to drain the main. Most plants drain a main through a drain valve or a cleanout and need no actuator, which is why it is not furnished by default; a plant that uses one takes on the risk that the disc is left held open and the station floods on the next stop. {note}
+
+### Where a backflow actuator is furnished, it shall hold the disc fully open against the rated working pressure on the downstream face, shall be lockable in the released position, and shall show whether the disc is held or free from the operating floor.
+
+# Resilient-Hinge Rubber Flapper Check Valves {toc}
+
+## Requirements in this section apply to every resilient-hinge rubber flapper check valve furnished under this standard, whether selected in the datasheet for a service or designated for a particular valve on the valve schedule. {note}
+
+## Rubber flapper check valves shall have a one-piece disc of elastomer molded around a steel reinforcing plate, hinged by the flex of the elastomer itself across the top of the disc and seating on a seat machined in the body at an angle of not more than 45° from vertical, so that the disc travels through a short arc to close.
+
+## The body shall be of ductile iron conforming to ASTM A536 or gray cast iron conforming to ASTM A126 Class B, with a full waterway, with no internal hinge pin, shaft, or bushing, and with a bolted cover through which the disc is removed and replaced without removing the body from the line.
+
+## The flapper elastomer shall be as indicated in the datasheet.
+
+```datasheet
+label: Rubber Flapper Elastomer
+type: select
+options:
+ - "Nitrile (Buna-N)"
+ - "Neoprene"
+ - "EPDM"
+ - "Fluoroelastomer"
+default: "Nitrile (Buna-N)"
+```
+
+## The flapper is both the seal and the hinge, so its compound is chosen for the flex life in the fluid as much as for the seal. Nitrile is the compound nearly every flapper valve is molded in, resists the grease and oil of raw sewage, and is the default; EPDM is selected on chlorinated and chloraminated water where nitrile swells over years, neoprene where a utility's stock is neoprene, and fluoroelastomer on a chemical line, at several times the cost and with a shorter flex life. {note}
+
+## The flapper shall be rated by its manufacturer for the service fluid and the service temperature indicated for the valve on the valve schedule, shall conform to ASTM D2000 for the compound selected, and in potable water service shall be of a compound certified to NSF/ANSI/CAN 61.
+
+## Rubber flapper valves shall be furnished for the rated working pressure indicated in the datasheet for the valve, and shall not be furnished in a size or at a pressure beyond the range the manufacturer publishes for the flapper reinforcement.
+
+## Rubber flapper valves furnished with a position indicator or a limit switch shall have the indicator or switch driven by a mechanical follower on the disc that carries no flow load, and the follower shall be sealed through the cover with a replaceable seal.
+
+## Rubber flapper valves shall be furnished with a backflow device where the valve schedule designates one for a valve, consisting of a screw through the cover that holds the disc off its seat and is lockable in the released position.
+
+## The flapper valve's advantage over a swing check is the absence of a hinge pin, which is the swing check's wearing part and the one that seizes, and its 45° seat and short travel are what let it close before the column reverses on most mains without a lever or a weight. Its limit is the reinforced rubber disc, which carries the reverse pressure as a plate and sets the pressure and the size the valve is made in, and a plant that needs a flapper valve above that range needs a different type. {note}
+
+# Tilting-Disc Check Valves {toc}
+
+## Requirements in this section apply to every tilting-disc check valve furnished under this standard, whether selected in the datasheet for a service or designated for a particular valve on the valve schedule. {note}
+
+## Tilting-disc check valves shall have a disc pivoted on trunnions located above the disc centerline and off the seat plane, so that the disc tilts open through a short arc with the flow and closes by gravity and by the pressure imbalance across it as the flow decays, with no external lever required for closure.
+
+## The body shall be of ductile iron conforming to ASTM A536, gray cast iron conforming to ASTM A126 Class B, or cast steel, as the manufacturer's design for the rated working pressure provides, with a flow area through the open valve not less than that the manufacturer publishes for the size and a head loss curve submitted with the product data.
+
+## The disc and the body seat ring shall carry a metal-to-metal seat of bronze on bronze or stainless steel on stainless steel, lapped to seal at the rated working pressure, or a resilient seat where the manufacturer's design for the size provides one and the valve schedule designates it.
+
+## The trunnions shall be of stainless steel conforming to ASTM A276 and shall turn in bushings of bronze or stainless steel, galvanically compatible with the trunnions in the service fluid, replaceable through the cover or the body joint without removing the body from the line.
+
+## Tilting-disc check valves shall be furnished with the dashpot provision indicated in the datasheet, except where a different provision is designated for a particular valve on the valve schedule to deliver its closure response.
+
+```datasheet
+label: Tilting-Disc Dashpot
+type: select
+options:
+ - "None"
+ - "Top-mounted dashpot controlling the opening and closing travel"
+ - "Bottom-mounted dashpot controlling the final closing travel"
+ - "Top-mounted and bottom-mounted dashpots"
+```
+
+## A tilting disc without a dashpot closes faster than any swing check, which is why it is bought, and the speed of that closure is itself the pressure rise where the main is long and the head is high. A top-mounted dashpot slows both the opening and the closing through an oil cylinder on a shaft extended from the trunnion; it damps the disc flutter of a pump that runs at the edge of its curve and controls the closure where the whole travel has to be timed. A bottom-mounted dashpot acts only over the last part of the closing travel, through a piston the disc strikes, and it is the arrangement where a fast free closure is wanted and only the seat impact is to be cushioned. Both are fitted where the surge analysis calls for a two-stage closure, fast through the first part and timed through the last. The provision follows the surge analysis of each pump discharge, which is why none is defaulted. {note}
+
+## Where a dashpot is furnished, it shall be oil-filled, fitted with an adjustable orifice setting the controlled travel time, a sight gauge or dipstick, and a fill port reachable with the valve installed, and shall be rated for the service temperature range of the location.
+
+## Tilting-disc valves shall be furnished with the position indicator and limit switch provisions selected under this standard, driven from the trunnion shaft extended through a sealed bearing.
+
+# Silent and Nozzle Check Valves {toc}
+
+## Requirements in this section apply to every silent spring-loaded center-guided check valve and every nozzle check valve furnished under this standard, whether selected in the datasheet for a service or designated for a particular valve on the valve schedule. {note}
+
+## Silent check valves shall conform to MSS SP-125 and shall close a spring-loaded disc guided on a central stem or on the body bore, so that the disc is seated before the flow in the line reverses.
+
+## Nozzle check valves shall be of the manufacturer's published venturi-body design, with a short-travel spring-loaded disc or ring guided on a central diffuser, and shall be shell and seat tested at the pressures of MSS SP-125.
+
+## The body style of silent check valves shall be as indicated in the datasheet.
+
+```datasheet
+label: Silent Check Body Style
+type: select
+options:
+ - "Wafer, between flanges"
+ - "Globe-style flanged body"
+ - "Flanged nozzle body"
+```
+
+## A wafer silent check is the shortest and lightest check valve made, costs the least, and is clamped between two flanges it cannot be removed from without unbolting the line; its disc travel is short and its head loss is the highest of the three. A globe-style flanged body carries the same spring-loaded disc in a body that bolts to the line independently and holds pressure with either flange removed, at a laying length that fits where a swing check fits. A flanged nozzle body shapes the flow through a venturi so that the disc or ring travels a few inches on a straight diffuser, at the lowest head loss of any spring-closed valve and the fastest closure of any check valve, and it is the body of the large high-service pump discharge where both the slam and the energy cost of head loss have been computed. {note}
+
+## The spring of each silent and nozzle check valve shall be of Type 316 stainless steel, selected by the manufacturer for the valve size, the flow range of the pump, and the deceleration stated for the valve, so that the disc is closed before the column reverses and so that the disc is held fully open, without flutter, at the minimum flow the pump delivers.
+
+## The disc shall be of bronze conforming to ASTM B62, ductile iron conforming to ASTM A536, or stainless steel conforming to ASTM A743 Grade CF8M, as the manufacturer's design for the body material provides, and the seat shall be as indicated in the datasheet.
+
+```datasheet
+label: Silent Check Seat Type
+type: radio
+options:
+ - "Resilient seat, elastomer on the disc"
+ - "Metal-to-metal seat, bronze or stainless steel"
+```
+
+## A silent check closes under spring force rather than under reverse pressure, so a resilient seat gives it the drop-tight seal a metal seat on a spring cannot, at the cost of the one wearing part, and a metal seat is chosen where the fluid is hot or chemical or where the line tolerates the weep. Neither is the norm across the services these valves serve. {note}
+
+## The disc guide and the spring of silent and nozzle check valves shall be replaceable with the body left in the line for flanged bodies, and the valve shall be furnished with the head loss curve across its flow range for the product data.
+
+## A silent check is a valve that nobody sees working, which is both its virtue and its limit: it has no lever, no position indication, no cushion, and no adjustment, and it is selected on the strength of the manufacturer's spring selection alone. A spring too light lets the disc flutter at low flow and wears the guide; a spring too heavy costs head on every hour the pump runs. The deceleration on the valve schedule is what the manufacturer selects against, and the minimum pump flow is what keeps the disc off the stop. {note}
+
+# Dual-Disc Wafer Check Valves {toc}
+
+## Requirements in this section apply to every dual-disc check valve furnished under this standard, whether selected in the datasheet for a service or designated for a particular valve on the valve schedule. {note}
+
+## Dual-disc check valves shall conform to the design standard indicated in the datasheet.
+
+```datasheet
+label: Dual-Disc Check Design Standard
+type: radio
+options:
+ - "AWWA C518"
+ - "API 594"
+default: "AWWA C518"
+```
+
+## AWWA C518 is the waterworks standard for the dual-disc valve and carries the pressure rating, the materials, and the shell and seat tests that match the rest of a water plant's valves, which is why it is the default. API 594 describes the same valve for industrial piping, in the body materials and pressure classes of steel piping, and it is selected on a chemical, hot, or high-pressure industrial line where the AWWA materials do not serve. {note}
+
+## Dual-disc check valves shall close two spring-loaded half discs on a central hinge pin, with the discs seated before the flow reverses, with the springs, the hinge pin, and the stop pin of Type 316 stainless steel, and with the pins retained in the body so that they cannot be ejected under reverse pressure.
+
+## The body shall be of ductile iron conforming to ASTM A536, gray cast iron conforming to ASTM A126 Class B, cast steel, or stainless steel conforming to ASTM A743 Grade CF8M, as the design standard and the valve schedule provide for the service, in a wafer or a lug pattern as selected under this standard for the end connection.
+
+## The seat of dual-disc check valves shall be as indicated in the datasheet.
+
+```datasheet
+label: Dual-Disc Check Seat Type
+type: radio
+options:
+ - "Resilient seat, elastomer bonded in the body"
+ - "Metal-to-metal seat"
+```
+
+## A resilient seat bonded in the body seals drop-tight on half discs that close under spring force and is the seat of nearly every waterworks dual-disc valve; a metal seat is chosen on hot and chemical industrial lines where no elastomer serves, and it weeps. Neither is the norm across the services these valves serve. {note}
+
+## Dual-disc check valves shall be furnished with the lug pattern wherever the valve is installed at a dead end or at an equipment connection that is removed for service, and the lugs shall be rated for the full rated working pressure with the downstream flange removed.
+
+## The dual-disc valve puts the shortest laying length and the lowest weight of any check valve between two flanges, which is why it is the check valve of a process line in a crowded gallery. Its half discs close fast under their springs and its hinge pin carries the reverse pressure of both discs, so on a pump discharge it is a fast-closing valve with no cushion and no adjustment, and the surge analysis decides whether that closure is acceptable before it is scheduled there. {note}
+
+# Ball Check Valves {toc}
+
+## Requirements in this section apply to every ball check valve furnished under this standard, whether selected in the datasheet for a service or designated for a particular valve on the valve schedule. {note}
+
+## Ball check valves shall have a body of ductile iron conforming to ASTM A536 or gray cast iron conforming to ASTM A126 Class B, with a full-bore passage through which a sphere of the nominal pipe diameter passes with the ball lifted, with the ball guided into a pocket clear of the flow when open, and with a bolted access cover through which the ball and the seat are removed and replaced without removing the body from the line.
+
+## The ball shall be of the construction indicated in the datasheet.
+
+```datasheet
+label: Ball Check Ball Construction
+type: select
+options:
+ - "Hollow steel ball with a vulcanized nitrile cover"
+ - "Solid elastomer ball"
+ - "Phenolic resin ball"
+```
+
+## A hollow steel ball with a vulcanized nitrile cover is the ball of nearly every sewage and sludge ball check, because its weight is set by the wall of the steel shell so that it sinks in the fluid and reseats by gravity, and its cover seals on grit and resists the grease. A solid elastomer ball is the ball of the small grinder station valve and of a chemical line, is lighter, and seats under reverse flow more than under its own weight. A phenolic ball is selected on hot or chemical lines where an elastomer cover does not serve, and it seals metal-to-resin rather than on a compliant surface. The ball is matched to the fluid's density as well as its chemistry, which is why no construction is defaulted. {note}
+
+## The ball shall be of a specific gravity greater than that of the service fluid at the service temperature so that it reseats by gravity when the flow stops, and the manufacturer shall state the ball's specific gravity and the fluid it was selected for on the product data.
+
+## The seat shall be a renewable ring of bronze, stainless steel, or elastomer-faced metal, retained in the body and replaceable through the access cover, and shall be rated for the rated working pressure applied to the downstream face.
+
+## Ball check valves shall be installed with flow upward through a vertical valve, or horizontally with the ball pocket above the flow path, as the manufacturer publishes for the size, and shall not be installed with flow downward.
+
+## A ball check has no hinge, no pin, no spring, and no seat ledge for a solid to pack onto, and it clears itself on every cycle, which is why it is the valve of sludge and grit and of the pulsing discharge of a positive displacement pump. It is also the noisiest check valve made, because the ball lands on its seat on every stop, it does not indicate its position, and it accepts no lever, no switch, and no cushion, so a plant that wants to know whether a sludge pump is moving sludge looks at the pump rather than the valve. {note}
+
+# Foot Valves {toc}
+
+## Foot valves shall be furnished at the suction inlet of each suction-lift pump where indicated on [[drawing: the pump suction piping details]].
+
+## Foot valves shall combine a check valve with an inlet strainer in one body, shall hold the suction column against drain-back at the static lift of the installation with the pump stopped, and shall open at a flow and a pressure differential low enough that the pump's net positive suction head available is not reduced below the value the pump standard requires.
+
+## The strainer shall have a net open area not less than three times the area of the suction pipe, with openings smaller than the largest solid the pump passes, and shall be removable from the valve body for cleaning.
+
+## The foot valve body, the disc, and the strainer shall be of the material indicated in the datasheet.
+
+```datasheet
+label: Foot Valve Body and Strainer Material
+type: select
+options:
+ - "Bronze, ASTM B62"
+ - "Type 304 stainless steel"
+ - "Type 316 stainless steel"
+ - "Ductile iron, AWWA C550 coated, with a stainless steel strainer"
+```
+
+## A foot valve sits wetted at the bottom of a wet well or a tank for its whole life and is reached only by pulling the suction pipe, so its material is chosen for the fluid it sits in rather than for the pressure it holds. Bronze is the body of the small foot valve in clean water and resists the biofouling of a raw water intake better than stainless. Type 304 serves treated water and Type 316 the chloride and sulfide of a wastewater wet well or a brackish intake. A coated ductile iron body is the economical body in the large sizes, with a stainless strainer because the strainer cannot be coated. No material is the norm across the intakes and wells this standard serves. {note}
+
+## The foot valve disc shall be resilient seated, of a compound rated for the fluid and the temperature of the intake, and shall be replaceable with the strainer removed.
+
+## The foot valve is what makes a suction-lift pump start: without it the suction pipe drains between runs and the pump has to prime itself on every start, which a centrifugal pump cannot do and a self-priming pump does at the cost of its seal. The strainer is what keeps the foot valve closing, because a stick across the disc is a pump that loses its prime every night. {note}
+
+# Rubber Duckbill Check Valves {toc}
+
+## Rubber duckbill check valves shall be furnished at the outfalls, overflows, tide gates, and drain discharges indicated on [[drawing: the outfall and overflow details]].
+
+## Duckbill check valves shall be of one-piece construction, of an elastomer reinforced with synthetic fabric plies, flattening to a closed bill under reverse head and opening to a passage of the flow area the manufacturer publishes under forward head, with no mechanical hinge, pin, seat, or spring.
+
+## Duckbill check valves shall be mounted as indicated in the datasheet.
+
+```datasheet
+label: Duckbill Check Mounting
+type: select
+options:
+ - "Slip-on over the pipe end, secured with stainless steel clamps"
+ - "Flanged, bolted to the pipe flange"
+ - "Flanged, bolted to a wall thimble or a headwall plate"
+```
+
+## A slip-on duckbill is clamped over the outside of a pipe end and is the lowest-cost mounting and the quickest to replace, and it depends on the clamps alone to hold the valve against the reverse head. A flanged duckbill bolts to the pipe flange with a full-face elastomer flange of its own and holds the full reverse head through the bolts, which is why it is the mounting of a submerged outfall and of any discharge the tide stands on. A wall thimble or headwall mounting bolts the valve to the structure where there is no pipe end to mount on, as at a channel wall or an overflow weir discharging through a wall. The mounting follows the structure at each outfall rather than the valve. {note}
+
+## The duckbill elastomer shall be as indicated in the datasheet.
+
+```datasheet
+label: Duckbill Check Elastomer
+type: select
+options:
+ - "Neoprene"
+ - "EPDM"
+ - "Nitrile (Buna-N)"
+ - "Chlorobutyl"
+default: manufacturer
+```
+
+## Neoprene is the compound most duckbill valves are molded in and resists the weather, the sunlight, and the seawater of an outfall; EPDM carries greater ozone and ultraviolet resistance where the valve is exposed above water, nitrile resists the oil and grease of a combined sewer or an industrial discharge, and chlorobutyl resists the chemistry of a treated effluent or a chemical drain. The manufacturer's standard compound serves the ordinary outfall, which is why the manufacturer's selection is acceptable, and a project whose discharge or exposure calls for another records it here. {note}
+
+## Each duckbill valve shall be rated by its manufacturer for the maximum reverse head indicated for the location on the outfall and overflow details, shall open at a forward head not greater than the head the manufacturer publishes for the size, and shall be furnished with the published head loss curve for the product data.
+
+## Duckbill valves at a submerged outfall shall be furnished with the bill oriented as the manufacturer publishes for the current and wave exposure of the location, and shall be furnished with a support where the manufacturer's data requires one for the size and the cantilever.
+
+## A duckbill has no moving part to foul and seals on a stone or a rag, which is why it is the check valve of an outfall that the tide, the river, or the receiving channel would otherwise back into the pipe. It opens a little under a small head and a lot under a large one, so the storm flow passes and the trickle does not drain the pipe, and its cost is a head loss at low flow that a steel flap gate does not have and a fabric body that is cut by a sharp object and by the sun. {note}
+
+# Position Indication and Supervisory Contacts {toc}
+
+## Pump discharge check valves of a type that carries an outside lever or a shaft extension shall be furnished with the position provision indicated in the datasheet.
+
+```datasheet
+label: Position Indication and Limit Switches on Pump Discharge Check Valves
+type: select
+options:
+ - "None beyond the outside lever"
+ - "Limit switch signaling the closed position"
+ - "Limit switches signaling the open and closed positions"
+ - "Limit switches signaling open and closed positions and a continuous position transmitter"
+```
+
+## An outside lever and weight shows the disc position to anyone in the gallery, and on most plants that is all the indication a check valve carries. A closed-position switch tells the supervisory system that the pump has stopped moving water, which is the signal a station uses to detect a pump that is running against a closed valve or a valve that has not closed on a stop, and it is the switch most often bought. Open and closed switches let the system see the valve stroke on every start and stop, and a continuous transmitter lets it see a disc that is throttling on a pump running off its curve or a disc that is closing slowly as a hinge wears. The points a station reads follow its control narrative rather than the valve, which is why none is defaulted. {note}
+
+## Limit switches shall be driven by the hinge pin shaft or the trunnion shaft, outside the body, through a cam or a lever that carries no flow load and that is adjustable without disassembly, and shall not be mounted on the lever weight or the lever arm.
+
+## Limit switch and transmitter housings shall be rated under NEMA 250 to the enclosure type selected under [[sync/common-work-results-process]] for equipment-mounted electrical devices, and housings on valves in a wet well, a vault subject to flooding, or a classified location shall be rated for that location as that standard requires.
+
+## The wiring of limit switches and transmitters, and the supervisory points they serve, shall be installed and integrated under [[sync/control-systems-integration]].
+
+## Where the valve schedule designates a limit switch on a ball check, a silent check, a dual-disc check, or any other valve of a type that carries no outside shaft, the valve shall be furnished with a flow switch or a differential pressure switch across it in place of a limit switch, as the manufacturer's design provides.
+
+# Bolting {toc}
+
+## The cover and body bolting of each valve shall be of the material indicated in the datasheet.
+
+```datasheet
+label: Cover and Body Bolting
+type: select
+options:
+ - "Zinc-plated carbon steel"
+ - "Type 304 stainless steel"
+ - "Type 316 stainless steel"
+```
+
+## Zinc-plated carbon steel bolting shall conform to ASTM A307, and stainless steel bolting shall conform to ASTM F593, Alloy Group 1 for Type 304 and Alloy Group 2 for Type 316.
+
+## Bolting on buried, submerged, wet well, and vault-installed valves shall be stainless steel regardless of the datasheet selection.
+
+## Plated carbon steel is the bolting a valve ships with and serves a dry, heated gallery where it is inspected and painted with the valve. Type 304 holds up in the damp, hydrogen sulfide atmosphere of a wet well or a sludge gallery, where plated steel rusts within a few years and a seized cover bolt turns a seat replacement into a body replacement. Type 316 adds resistance to chlorides and is selected in a chlorinated water gallery, near the coast, or wherever the plant standardizes on it. The decision follows the atmosphere the valves sit in, which the project knows and the standard does not. {note}
+
+## Stainless steel bolting shall be assembled with an anti-seize compound on the threads.
+
+# Coatings and Linings {toc}
+
+## Shop Coating System {toc}
+
+### Ferrous interior and exterior surfaces of each valve body, cover, and disc, except seating surfaces, bearing surfaces, and machined flange faces, shall be coated at the factory in accordance with AWWA C550 with the system indicated in the datasheet.
+
+```datasheet
+label: Shop Coating System on Ferrous Surfaces
+type: select
+options:
+ - "Fusion-bonded epoxy, AWWA C550"
+ - "Two-part liquid epoxy, AWWA C550"
+ - "Not applicable, corrosion-resistant alloy body and disc"
+default: manufacturer
+```
+
+### 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 and is the system a manufacturer uses where its castings are too large to heat. 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, bronze, or aluminum bronze body and disc are not coated. {note}
+
+### Shop coatings on valves in potable water service shall be certified to NSF/ANSI/CAN 61.
+
+### 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.
+
+### 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.
+
+### Stainless steel, bronze, aluminum bronze, and nickel-copper surfaces shall not be coated.
+
+## Exterior Finish on Exposed Valves {toc}
+
+### The exterior finish on valves in exposed service shall be as indicated in the datasheet.
+
+```datasheet
+label: Exterior Finish, Exposed Valves
+type: radio
+options:
+ - "Shop epoxy as the finished coating"
+ - "Shop epoxy as the primer for a field-applied finish coat"
+```
+
+### The shop epoxy is a complete corrosion barrier on its own and is the finished exterior on a valve in a vault or a gallery where nobody looks at it. In a plant whose piping is color-coded or finished to a scheme, the valve exterior is topcoated in the field to match the pipe, and the shop epoxy becomes the primer that topcoat has to bond to. The decision follows the plant's finish scheme rather than the valve. {note}
+
+### Where the datasheet selects a field-applied finish coat, the shop epoxy shall be compatible with the finish coat system furnished under [[sync/high-performance-coatings]], and the valve manufacturer shall state the surface preparation the finish coat requires over its epoxy.
+
+### Where the datasheet selects a field-applied finish coat, the lever, the weight, and the dashpot shall be finished in the field under [[sync/high-performance-coatings]] in the color the finish scheme assigns to valve operators, with the lever's factory setting mark preserved.
+
+# Buried Service Provisions {toc}
+
+## Each buried check valve shall be installed with the access indicated in the datasheet, except where the valve is installed on a site distribution main whose vault is furnished under [[sync/water-distribution-piping]].
+
+```datasheet
+label: Buried Check Valve Access
+type: radio
+options:
+ - "Precast concrete valve vault with an access cover"
+ - "Direct burial with a free-swinging disc and no external provisions"
+```
+
+## A vault puts the cover, the lever, the dashpot, and the switches where a crew reaches them, which is the only way a lever-and-weight or a cushioned valve is adjusted after the trench is closed, and it is the access of nearly every buried pump discharge valve, at the cost of the structure and the confined-space entry it creates. Direct burial is the position for a free-swinging swing or flapper check on a yard line that is never adjusted and is dug up to be serviced, and it is chosen on a long yard main where a vault would be a structure for a valve nobody visits. The choice follows the valve's provisions rather than the project, which is why neither is defaulted. {note}
+
+## Buried valves shall be installed at the depth of the main they are set in, whose depth of cover is set below [[parameter: frost-depth]] by the standard governing the main.
+
+## Direct-buried valves shall have mechanical joint ends unless the connected main is flanged, shall carry no outside lever, weight, spring, dashpot, backflow actuator, or limit switch, and shall be polyethylene encased in accordance with AWWA C105 / A21.5 where the connected main is encased, with the encasement continuous over the valve body and the joints.
+
+## Valves installed in a vault shall be set with the cover, the lever, and the dashpot reachable from the vault floor or the access opening without disconnecting piping, and the vault shall be sized so that the cover can be removed and the closure member withdrawn with the valve in place.
+
+## A check valve carries no operating nut, so no valve box, extension stem, or operating key is furnished for a buried check valve, and the valve box articles of the isolation valve standards do not apply to it. {note}
+
+## The orientation and the type of each buried valve shall be recorded on the record drawings before the trench is backfilled, with not fewer than two tie dimensions to permanent surface features.
+
+# Factory Testing {toc}
+
+## Production Tests {toc}
+
+### Each valve shall be hydrostatically shell tested at the factory with the closure member open, in accordance with the governing design standard for its type and at not less than 1.5 times the rated working pressure, for the duration that standard prescribes, with no leakage through the body, the cover joint, or the shaft seals.
+
+### Each valve shall be seat tested at the factory with the closure member closed and the rated working pressure applied to the downstream face, for the duration the governing design standard prescribes, with no leakage past the seat beyond the limit that standard allows for the seat type.
+
+### Valves of a type with no consensus product standard shall be shell and seat tested at the pressures and for the durations of AWWA C508 for a swing, tilting-disc, flapper, or ball valve and of API 598 for an industrial valve, and duckbill valves shall be tested for reverse head holding at the rated reverse head of the location.
+
+### Each valve with an outside lever, a spring, a dashpot, or a limit switch shall be operationally tested at the factory by cycling the closure member through full travel, and the lever setting, the dashpot fill and setting, the stops, and the switch operation shall be verified during that cycle.
+
+### The seat test is applied in the reverse direction because that is the only direction a check valve ever holds, and a valve that passes its shell test and fails its seat test has a disc that is landing off its seat, a seat ring that is not seated in the body, or a hinge that is holding the disc up, all of which are found before shipment or in the wet well. {note}
+
+### 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.
+
+### Certified test reports identifying each valve by serial number shall be furnished for every valve before shipment, and no valve shall be shipped without one.
+
+## Test Witnessing {toc}
+
+### Factory tests shall be witnessed on the basis selected under [[sync/common-work-results-process]], and the valves designated for witnessed testing shall be as indicated on [[drawing: the valve schedule]].
+
+### A check valve's factory test is a shell test and a seat test on a product tested to a consensus standard in a factory with a quality system, and a certified report is what nearly every project accepts for it. Witnessing is bought for the large pump discharge valves whose closure response a project wants to see cycled with the dashpot set, and the valve schedule designates them. {note}
+
+# Delivery, Storage, and Handling {toc}
+
+## Valves shall be shipped with the closure member blocked or secured in the position the manufacturer designates for shipment, with the end openings covered to keep debris off the seat, with the lever weight removed and tagged or secured against swinging, and with the covers left in place until the valve is set in the line.
+
+## Valves shall be lifted by the body, by lifting lugs the manufacturer provides, or by slings around the body, and shall not be lifted by the lever, the weight, the dashpot, the shaft, the limit switch, or the cover bolts.
+
+## Valves shall be stored off the ground on timbers or pallets, under cover, with the dashpot and the switches protected from weather, and valves with elastomer seats, flappers, balls, or duckbill bodies shall be stored out of direct sunlight and away from ozone sources such as motors and welding equipment.
+
+## Rubber takes a set where it is compressed and left, and it degrades under ultraviolet light; a flapper valve stored closed in the sun for a construction season arrives at the line with a disc that has already lost the resilience it seals and hinges with. The manufacturer's shipping position relieves the seat, and the cover keeps the sun off it. {note}
+
+## Each valve shall be delivered with its certified test reports, its mechanical joint accessories where furnished, its lever, weight, spring, and dashpot where furnished, and its limit switches where furnished, and the Contractor shall verify the delivery against the approved submittal before the valve is moved to the piping.
+
+## The Contractor shall bear the cost of repairing or replacing a valve damaged in delivery, storage, or handling.
+
+# Installation {toc}
+
+## Orientation and Location {toc}
+
+### Each valve shall be installed with the flow arrow in the direction of flow and in the orientation shown on the accepted submittal drawings, and a valve of a type the manufacturer publishes as limited to horizontal piping, or to vertical piping with upward flow, shall not be installed otherwise.
+
+### Swing, tilting-disc, and rubber flapper check valves in horizontal piping shall be installed with the hinge pin or the trunnions horizontal and the closure member hanging from the top of the body, and in vertical piping only with the flow upward.
+
+### Swing check valves in wastewater, sludge, scum, and grit service shall be installed in horizontal piping wherever the piping layout permits, and where a swing check in solids service must be installed in vertical piping, the valve schedule shall designate it and the manufacturer shall confirm the valve for that orientation.
+
+### Ball check valves shall be installed with flow upward through a vertical valve, or in horizontal piping with the ball pocket above the flow path, as the manufacturer publishes for the size.
+
+### A swing check installed in vertical piping with the flow downward hangs its disc open under gravity and never closes, and a swing check in horizontal solids service installed with its hinge at the bottom collects the solids on its disc and seat on every stop. The orientation is a property of the type, and the piping layout accommodates it. {note}
+
+### Each pump discharge check valve shall be installed between the pump and its isolation valve, downstream of any air release or air/vacuum valve on the pump discharge, so that the pump and the check valve are isolated from the main by one valve and the check valve is removed with the pump isolated.
+
+### Each pump discharge check valve shall be installed with not less than the length of straight pipe upstream of the valve that the manufacturer publishes for the type and size, and where the valve is installed closer than that to the pump discharge elbow, a reducer, or a tee, the Contractor shall obtain the manufacturer's written confirmation of the valve for that location before it is installed.
+
+### A check valve closes its disc against the flow pattern that reaches it, and a disc fed by the swirl off a pump elbow or a reducer flutters open and shut on every revolution, wears its hinge, and is still moving when the pump stops. The manufacturers publish the straight length each type needs, and a station too tight to provide it is the station where a nozzle check or a silent check with a shorter requirement is chosen. {note}
+
+## Piping Connections and Support {toc}
+
+### Flanged valves shall be installed with the mating flanges aligned, parallel, and concentric before the bolts are tightened, and the valve shall not be used to draw misaligned piping together.
+
+### Wafer and lug valves shall be centered between the mating flanges with the closure member in the position the manufacturer designates for installation, and the flange bolts shall be tightened evenly in a crossing pattern in not fewer than three passes.
+
+### Before a wafer, lug, swing, or dual-disc valve is set, the Contractor shall verify that the inside diameter of the pipe, fitting, lining, or reducer on each side clears the closure member through its full travel, and where it does not, the Contractor shall install a spool or a spacer between the valve and the obstruction.
+
+### Flange bolting and gaskets at each valve shall be furnished and installed under the standard governing the piping, and shall be rated for the rated working pressure of the valve.
+
+### Where a valve is installed against a flat-faced cast iron or ductile iron flange, a full-face gasket shall be used and a raised-face mating flange shall not be used.
+
+### Valves 8 in. and larger, and every valve with a dashpot or a backflow actuator, shall be supported independently of the connected piping under the standard governing that piping, so that no piping load, thrust, or vibration is carried into the valve body.
+
+### Each exposed valve shall be installed with clearance for the cover to be removed, the closure member to be withdrawn, the lever and weight to swing through their full travel, and the dashpot and the switches to be serviced, and the clearance shall be not less than the manufacturer's published service clearance.
+
+### Each valve shall be installed with its closure member free, blocking removed, during flushing of the connected piping, and the Contractor shall remove any construction debris that lodges in the body before the pump is first started.
+
+## Field Closure Test {toc}
+
+### After installation and before a pump is released to performance testing, the Contractor shall demonstrate the closure of its discharge check valve on a normal stop of the pump and, where the station has standby power or the pump is on a variable frequency drive, on a simulated power failure stop, with the isolation valve open and the main at its operating pressure.
+
+### During the field closure test the Contractor shall adjust the lever weight position, the spring tension, or the dashpot orifice setting, within the range the manufacturer publishes, until the valve closes without slam and without holding the disc against the running pump, and the final setting shall be marked on the lever or the dashpot and recorded.
+
+### Where the valve schedule designates a closure response that the valve cannot be adjusted to deliver within the manufacturer's published range, the Contractor shall report the condition to the Engineer of Record in writing before the pump is released, and shall not alter the valve beyond the manufacturer's published range.
+
+### Each pump discharge check valve furnished with limit switches shall have the switches set during the field closure test so that the closed switch makes only with the disc on its seat and the open switch makes only with the disc at its stop, and the switch operation shall be verified at the supervisory system under [[sync/control-systems-integration]].
+
+### The field closure test of each valve shall be recorded on a report identifying the valve tag, the pump, the date, the persons present, each stop condition demonstrated, the initial and final settings, and any deficiency found and its correction, and the test shall be witnessed on the basis the Field Performance and Acceptance Testing section of [[sync/common-work-results-process]] sets for the pump it serves.
+
+### The weight on a lever is set at the factory from the manufacturer's experience and at the station from the station's own column, and the two are rarely the same. A stop with the weight too far in lets the disc slam; a weight too far out holds the disc partly closed against the running pump and shows up as a head the pump cannot make. The closure test on the real pump, under the real main, is where the number is found, and it is found before the station is in service rather than on the night the power fails. {note}
+
+### A valve that slams, fails to close, or leaks past its seat during the field closure test shall be corrected or replaced by the Contractor, and the retest shall be at the Contractor's cost, including the cost of the witnessing parties' attendance at the retest.
+
+## Piping Pressure Test {toc}
+
+### Installed valves shall be tested with the connected piping under the hydrostatic test of the standard governing that piping, with the closure member free.
+
+### Where a check valve forms the boundary of a piping test, the test pressure shall be applied to the downstream face of the closed closure member only, shall not exceed the rated working pressure of the valve, and a check valve shall not be used to hold a test pressure applied to its upstream face.
+
+### A check valve holds pressure in one direction, and the test pressure of the piping is set above the valve's rating by design. A check valve with the test on its upstream face opens and the test fails; a check valve with the test above its seat rating on its downstream face is damaged by the test it was never rated for. A blind flange is the test boundary, and the valve is tested free inside it. {note}
+
+# Warranty {toc}
+
+## The Contractor shall warrant each check valve, its lever, weight, spring, dashpot, backflow actuator, and limit switches against defects in materials and workmanship for the period indicated in the datasheet, measured from the date of substantial completion.
+
+```datasheet
+label: Valve Warranty Period
+type: range
+unit: years
+options:
+ min: 1
+ max: 5
+ setpoints: [1, 2, 3, 5]
+default: 1
+constraint: min
+```
+
+## Where the contract General Conditions or [[sync/common-work-results-process]] specify a longer warranty period than the datasheet, the longer period shall govern.
+
+## A valve that leaks past its seat at or below the rated working pressure, leaks through its shaft seals, cover joint, or body, slams on a stop at the setting recorded in the field closure test, or fails to close within the warranty period shall be repaired or replaced by the Contractor at no cost to the Owner.
+
+## The Contractor shall bear the cost of excavating and backfilling to reach a buried 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.
+
+## 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.
+
+## The cost that goes unassigned in a check valve warranty is never the valve. It is the pump that was lifted off its base by the slam, the main that split, and the wet well that flooded through a disc that did not close. Naming the slam at the recorded setting as a warranted failure is what makes the warranty worth having on a valve that cost less than the pump beside it. {note}
+
+# Spare Parts {toc}
+
+## The Contractor shall furnish the spare parts indicated in the datasheet, packaged, labeled with the valve size and type they fit, and delivered to the Owner before substantial completion.
+
+```datasheet
+label: Spare Parts Furnished
+type: checkbox
+options:
+ - "One seat ring or seat elastomer for each swing check size and seat type"
+ - "One flapper for each rubber flapper check size"
+ - "One ball for each ball check size"
+ - "One spring and disc for each silent, nozzle, and dual-disc check size"
+ - "One shaft seal set for each valve size with an outside lever or shaft extension"
+ - "One cover gasket for each valve size"
+ - "One dashpot seal kit and one fill of dashpot oil for each dashpot size"
+default:
+ - "One seat ring or seat elastomer for each swing check size and seat type"
+ - "One flapper for each rubber flapper check size"
+ - "One ball for each ball check size"
+ - "One cover gasket for each valve size"
+constraint: all_of
+```
+
+## Spare parts shall be the products of the valve manufacturer and shall be interchangeable with the parts installed in the valves furnished.
+
+## The seat, the flapper, and the ball are the parts a check valve wears, and the parts a crew replaces through the cover in an afternoon when the spare is on the shelf and in a month when it is not. A shaft seal set and a dashpot kit are held where the plant has levers and dashpots to service, and a spring and disc for a silent check are held where the plant has no other way to put a silent check back in service short of replacing it. {note}
+
+## The spare parts list, with the manufacturer's part numbers, shall be included in the operation and maintenance data.