1 Scope
NOTE This standard covers the materials, assembly types, installation, testing, certification, and ongoing maintenance documentation for backflow prevention assemblies installed on potable water systems within and serving commercial, institutional, and industrial buildings. (1.1)
NOTE The scope includes assemblies installed at the building water service entrance for premises (containment) protection, assemblies installed at internal cross-connections for in-plant (isolation) protection, and detector check assemblies installed on fire-service supply piping where the fire service is connected to a potable water main. (1.2)
NOTE This standard establishes the material, performance, installation, freeze-protection, and testing requirements that govern those drawings. (1.4)
NOTE Cross-connection control protects the potable water supply from contamination via two mechanisms: back-siphonage, in which a negative pressure event in the potable supply (main break, firefighting demand, high upstream flow on a small main) creates a vacuum that pulls liquid from a downstream source up into the supply; and back-pressure, in which a downstream system operating at a pressure higher than the supply (boilers, pumps, elevated tanks, chemical-feed pumps) pushes its contents back into the supply through any connection. (1.5)
1.6 The assembly type selected for a given cross-connection shall be matched to both the degree of hazard at the connection and the type of backflow that is possible.
1.7 The Engineer of Record shall identify every cross-connection in the project, classify each as high-hazard or low-hazard per the adopted plumbing code and the water purveyor's cross-connection control program, and specify the assembly type at each location.
1.8 Coordination
1.8.1 Coordinate domestic-water-side piping, isolation valves, and pressure conditions with Domestic Water Piping. 1.8.3 Coordinate water-heater expansion control with Water Heaters. 1.8.4 Coordinate hydronic system makeup-water backflow protection with Hydronic Piping. NOTE Fixture-side back-siphonage protection integral to listed plumbing fixtures and fittings — service-sink faucet vacuum breakers, deck-mounted hose-thread vacuum breakers integral to a faucet, and tank-type water closet anti-siphon fill valves — is addressed in
Plumbing Fixtures and is outside the scope of this standard.
(1.8.5) 2 Referenced Standards
2.1 Materials, components, assembly selection, installation, and field testing shall comply with the latest adopted edition of the following standards and codes.
| Standard |
Title |
| IPC |
International Plumbing Code, Section 608 — Protection of Potable Water Supply |
| UPC |
Uniform Plumbing Code, Section 603 — Cross-Connection Control |
| ASSE 1001 |
Performance Requirements for Atmospheric Type Vacuum Breakers |
| ASSE 1011 |
Performance Requirements for Hose Connection Vacuum Breakers |
| ASSE 1012 |
Performance Requirements for Backflow Preventers with Intermediate Atmospheric Vent (Dual-Check with Atmospheric Port / DCAP) |
| ASSE 1013 |
Performance Requirements for Reduced Pressure Principle Backflow Prevention Assemblies and Reduced Pressure Principle Fire Protection Backflow Prevention Assemblies |
| ASSE 1015 |
Performance Requirements for Double Check Backflow Prevention Assemblies and Double Check Fire Protection Backflow Prevention Assemblies |
| ASSE 1020 |
Performance Requirements for Pressure Vacuum Breaker Assembly |
| ASSE 1047 |
Performance Requirements for Reduced Pressure Detector Fire Protection Backflow Prevention Assemblies (RPDA / RPDA-II) |
| ASSE 1048 |
Performance Requirements for Double Check Detector Fire Protection Backflow Prevention Assemblies (DCDA / DCDA-II) |
| ASSE 1056 |
Performance Requirements for Spill-Resistant Vacuum Breakers |
| ASSE 5000 series |
Professional Qualifications Standards for Backflow Prevention Assembly Testers, Repairers, Surveyors, and Cross-Connection Control Program Administrators |
| AWWA C510 |
Double Check Valve Backflow Prevention Assembly |
| AWWA C511 |
Reduced-Pressure Principle Backflow Prevention Assembly |
| AWWA Manual M14 |
Recommended Practice for Backflow Prevention and Cross-Connection Control |
| USC FCCCHR Manual |
Manual of Cross-Connection Control, Foundation for Cross-Connection Control and Hydraulic Research, University of Southern California (current edition) |
| CSA B64.0 |
Definitions, General Requirements, and Test Methods for Backflow Preventers and Vacuum Breakers |
| CSA B64.1.1 |
Atmospheric Vacuum Breakers (AVB) |
| CSA B64.1.2 |
Pressure Vacuum Breakers (PVB) |
| CSA B64.1.3 |
Spill-Resistant Vacuum Breakers (SRVB) |
| CSA B64.4 |
Reduced Pressure Principle Backflow Preventers (RP) |
| CSA B64.5 |
Double Check Valve Backflow Preventers (DCVA) |
| CSA B64.6 |
Dual Check Valve Backflow Preventers (DuC) |
| CSA B64.10 |
Selection and Installation of Backflow Preventers |
| EPA Cross-Connection Control Manual |
U.S. Environmental Protection Agency, Cross-Connection Control Manual (EPA 816-R-03-002, current edition) |
| NSF/ANSI 61 |
Drinking Water System Components — Health Effects |
| NSF/ANSI/CAN 372 |
Drinking Water System Components — Lead Content |
| NFPA 13 |
Standard for the Installation of Sprinkler Systems (fire-service backflow requirements) |
| NFPA 24 |
Standard for the Installation of Private Fire Service Mains and Their Appurtenances |
| ASCE 7 |
Minimum Design Loads and Associated Criteria for Buildings and Other Structures (seismic restraint of assemblies) |
2.2 Where the contract documents, the AHJ, the water purveyor's cross-connection control program, or a referenced standard impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
2.3 The applicable plumbing code (IPC Section 608 or UPC Section 603 as adopted by the jurisdiction) and the water purveyor's published cross-connection control requirements shall take precedence over all other references on any matter directly addressed.
3 Submittals
3.1 Action Submittals
3.1.1 Contractor shall submit the following for the Engineer's review prior to procurement and installation:
- Product data for each backflow prevention assembly, identifying the manufacturer, model number, assembly type (RPZ, DCVA, PVB, SVB, AVB, DCAP, DCDA-II, RPDA-II), size, body and trim materials, end-connection type, maximum operating pressure and temperature, the ASSE standard the assembly is listed to (ASSE 1013, 1015, 1020, 1056, 1012, 1001/1011, 1048, 1047), the AWWA standard where applicable (C510 or C511), and confirmation of inclusion on the USC FCCCHR approved assemblies list and any state-specific approved list applicable to the jurisdiction
- Confirmation of NSF/ANSI 61 and NSF/ANSI/CAN 372 certification for all wetted parts of every assembly installed on potable water service
- Sizing calculations for each RPZ assembly demonstrating that the relief-valve discharge can be carried away by the indirect waste receptor at the worst-case relief-valve discharge rate, with the calculation method per the assembly manufacturer's published guidance or USC FCCCHR Manual
- Product data for heated enclosures where assemblies are installed outdoors or in unconditioned spaces subject to freezing, including the enclosure's insulation R-value, heater type and wattage, internal volume, drain provisions, lock-and-key configuration, and ASSE 1060 (where applicable) or equivalent listing
- Layout and elevation drawings showing each assembly's installation, including the upstream and downstream shut-off valves, test cocks, air gap or indirect-waste receptor for RPZ relief discharge, support structure, and required clearances for testing access
- Tester certification documentation — current certification credentials of every individual who will perform initial commissioning testing of installed assemblies, conforming to the applicable ASSE 5110 (Tester) certification or the state-specific equivalent (each state administers its own program — examples include California AWWA, Florida DEP, USC FCCCHR Specialist, and individual state cross-connection control programs)
- Where assemblies are pre-installed in a packaged skid, hot-box, vault, or pump room, complete shop drawings of the skid showing the assemblies, piping, supports, valves, drains, heat trace, instrumentation, and enclosure penetrations
☑ Backflow assembly product data with ASSE listing and USC FCCCHR approval
☐ NSF 61/372 certification for all wetted parts
☐ RPZ indirect-waste sizing calculations
☐ Heated enclosure product data (outdoor / freeze-prone installations)
☐ Installation layout and elevation drawings
☐ Tester certification credentials (ASSE 5110 or state equivalent)
☐ Shop drawings for packaged skid / vault / hot-box installations
3.1.2 Work shall not proceed on any backflow assembly installation until the corresponding submittals have been reviewed and returned.
3.1.3 Where the water purveyor maintains an approved-assemblies list, the submitted assemblies shall appear on that list for the assembly type and size specified.
3.2 Closeout Submittals
3.2.1 Contractor shall provide the following at substantial completion before the backflow prevention assemblies are accepted:
- As-built drawings showing the final location, orientation, and connection details of each assembly, with each assembly tagged with a unique identifier matching the field tag on the assembly
- Operation and maintenance (O&M) manuals for each assembly, including disassembly procedures, internal-parts diagrams with replacement part numbers, the manufacturer's recommended periodic inspection and maintenance schedule, and the manufacturer's troubleshooting guidance for common failure modes (chattering relief valve, leaking check, fouled poppet)
- Initial commissioning test reports for every installed assembly, performed and signed by an ASSE 5110 (or state-equivalent) certified tester, on the form required by the water purveyor or the AHJ, documenting the test pressure values for each check, the relief-valve opening pressure, the assembly serial number, the tester's certification number and credential expiration, the date, the test-equipment calibration certificate number, and the pass/fail determination
- Documentation of submission of the initial commissioning test reports to the water purveyor and to the AHJ on the schedule required by their respective programs (typically within 10 to 30 days of installation)
- Tagging records for each assembly per the water purveyor's cross-connection control program — typically a permanent tag identifying the assembly type, size, serial number, installation date, and the next required test date — affixed to the assembly or installed at the assembly's location
- Warranty documentation for each assembly, indicating the manufacturer's warranty period from the date of substantial completion
☑ As-built drawings with unique assembly tags
☑ Operation and maintenance (O&M) manuals
☑ Initial commissioning test reports (ASSE 5110 certified tester)
☑ Submission of test reports to water purveyor and AHJ
☑ Permanent assembly tagging per cross-connection control program
☑ Warranty documentation
4 Quality Assurance
4.1 Installer Qualifications
4.1.1 Backflow prevention assembly installation shall be performed by journeyman plumbers licensed in the jurisdiction where the work is performed and supervised by a licensed plumbing contractor.
4.1.2 The Contractor's license shall be current and shall cover the full scope of work.
4.1.3 Where the water purveyor or AHJ requires individual installer certification or registration in a backflow prevention installer program, personnel shall hold current qualifying credentials.
4.2 Tester Qualifications
NOTE All field testing of backflow prevention assemblies — initial commissioning testing at installation, and any subsequent retesting performed by the Contractor during the construction warranty period — is governed by the following qualification requirements. (4.2.1)
ASSE 5110 — Backflow Prevention Assembly Tester (national)
USC FCCCHR Backflow Prevention Assembly Tester
AWWA Backflow Prevention Assembly Tester (state section)
State-administered tester certification program
Any of the above accepted by the AHJ and water purveyor
4.2.2 Field testing of backflow prevention assemblies shall be performed by a tester holding current certification under one of the following programs: ASSE 5110; USC FCCCHR Backflow Prevention Assembly Tester certification; AWWA Backflow Prevention Assembly Tester certification through a state section; or the state-administered tester certification program required by the jurisdiction.
4.2.3 The tester's credentials shall be current at the time of testing — an expired credential invalidates the test.
4.3 Test-Equipment Calibration
4.3.1 Differential-pressure test gauges used for field testing of backflow assemblies shall be calibrated against a master gauge or laboratory reference within the past 12 months, or on the calibration interval specified by the AHJ or water purveyor (some programs require calibration every 6 months).
4.3.2 A current calibration certificate shall be available at the test site for review by the AHJ inspector.
4.3.3 Test reports shall reference the calibration certificate number.
4.4 Lead-Free Compliance
4.4.1 All assemblies installed on potable water service shall be certified to NSF/ANSI/CAN 372, confirming that the weighted average lead content of the wetted surface area does not exceed 0.25 percent.
NOTE NSF/ANSI/CAN 372 lead-free certification is a federal requirement under the Reduction of Lead in Drinking Water Act (Section 1417 of the Safe Drinking Water Act) and is not subject to project-level waiver. (4.4.2)
4.4.3 Where any portion of a fire service draws makeup or initial fill from the potable supply, the fire-service assembly shall be certified to NSF/ANSI/CAN 372; assemblies in fire-service applications not interconnected to potable water need not be so certified.
4.5 Water Purveyor Approval
4.5.1 Each assembly shall appear on the approved-assemblies list maintained by the water purveyor (or by the state-level cross-connection control program that the purveyor recognizes).
NOTE In most US jurisdictions the approved-assemblies list is the USC FCCCHR approved-assemblies list; some states maintain their own additional lists. (4.5.2)
4.5.3 The Contractor shall confirm each proposed assembly's approval status before procurement.
4.5.4 Assemblies not on the applicable approved list shall not be installed even when they are listed by other certifying bodies.
4.6 Regulatory Inspection
4.6.1 Each backflow prevention assembly installation shall be available for inspection by the AHJ and by the water purveyor's cross-connection control inspector.
4.6.2 The Contractor shall coordinate inspection timing and shall not conceal, insulate, or enclose any portion of the assembly or its associated piping until inspections are complete and the work is released.
4.6.3 Assemblies installed in vaults, pits, or below-grade locations that require entry to inspect shall be installed with the access provisions complete and operational before the inspection request is submitted.
5 Selection of Assembly Type
5.1 Degree of Hazard
NOTE Cross-connections are classified by the degree of hazard the non-potable source represents to the public health. (5.1.1)
● High-hazard (health-hazard) — RPZ, RPDA-II, or air gap required
○ Low-hazard (non-health-hazard / pollution) — DCVA, DCDA-II, PVB, or higher acceptable
NOTE High-hazard (health-hazard) is a cross-connection to a substance that, if introduced into the potable supply, could cause illness, injury, or death — for example boilers with chemical water treatment, sewage and effluent systems, irrigation with fertilizer or pesticide injection, industrial process water containing chemicals, fire sprinkler systems with antifreeze or auxiliary water sources, hospital and laboratory equipment, and any previously contaminated system. (5.1.2)
NOTE Low-hazard (non-health-hazard, pollution) is a cross-connection to a substance that would impair the quality of the potable supply (taste, odor, color, temperature) but would not present a health risk — for example non-chemically-treated hydronic heating with no auxiliary water source, single-occupant residential irrigation without injection, ornamental fountains using only potable water, and similar systems where the only potential contamination is aesthetic. (5.1.3)
5.1.4 High-hazard cross-connections shall be protected by either a reduced-pressure principle assembly (RPZ/RPA) or an air gap.
5.1.5 Low-hazard cross-connections may be protected by a double-check valve assembly (DCVA), a pressure vacuum breaker (PVB), or a higher-rated device.
5.1.6 The Engineer of Record shall classify each cross-connection on the project, and the classification shall be documented in the project's cross-connection survey and on the backflow assembly schedule.
5.2 Type of Backflow
NOTE The type of backflow possible at a cross-connection determines which assembly types are acceptable, independent of the degree of hazard. (5.2.1)
○ Back-siphonage only (downstream system open to atmosphere, no booster pump or elevated source)
● Back-pressure possible (booster pump, boiler, elevated tank, chemical injection, or other pressurized downstream source)
NOTE In a back-siphonage-only condition, negative pressure in the potable supply could draw the downstream source backward into the supply, but the downstream system is open to atmosphere or otherwise not capable of operating at a pressure higher than the supply. (5.2.2)
5.2.3 Atmospheric vacuum breakers (AVB), pressure vacuum breakers (PVB), and spill-resistant vacuum breakers (SVB) protect against back-siphonage only and shall not be used where back-pressure is possible.
NOTE Where back-pressure is possible, the downstream system can be pressurized above the supply (boiler, pump, elevated tank, chemical injector, fire-pump system, irrigation with booster pump). (5.2.4)
5.2.5 Only assemblies with two independently-acting check valves (DCVA, RPZ, DCDA-II, RPDA-II) shall be used where back-pressure is possible; PVB, SVB, and AVB are not acceptable in back-pressure applications.
5.3 Assembly Selection Matrix
NOTE The following matrix summarizes acceptable assemblies for combinations of hazard and backflow type. (5.3.1)
| Degree of Hazard |
Backflow Type |
Acceptable Assemblies |
| High-hazard |
Back-pressure possible |
RPZ (ASSE 1013); air gap |
| High-hazard |
Back-siphonage only |
RPZ (ASSE 1013); air gap; PVB (ASSE 1020) or SVB (ASSE 1056) where code permits for the application |
| Low-hazard |
Back-pressure possible |
DCVA (ASSE 1015); RPZ |
| Low-hazard |
Back-siphonage only |
PVB (ASSE 1020); SVB (ASSE 1056); DCVA; RPZ |
| Fire service — high-hazard (chemical antifreeze, auxiliary supply, or AHJ classification) |
Back-pressure inherent |
RPDA-II (ASSE 1047) |
| Fire service — low-hazard |
Back-pressure inherent |
DCDA-II (ASSE 1048); RPDA-II |
| Premises isolation (service entrance, multi-family, commercial) |
Back-pressure presumed |
DCVA (light/medium commercial low-hazard); RPZ (commercial, industrial, healthcare, or any high-hazard occupancy) |
RPZ — Reduced Pressure Principle Assembly (ASSE 1013)
DCVA — Double Check Valve Assembly (ASSE 1015)
PVB — Pressure Vacuum Breaker Assembly (ASSE 1020)
SVB — Spill-Resistant Vacuum Breaker (ASSE 1056)
AVB — Atmospheric Vacuum Breaker (ASSE 1001 / 1011)
DCAP — Dual-Check with Intermediate Atmospheric Vent (ASSE 1012)
DCDA-II — Double Check Detector Assembly (ASSE 1048, fire service)
RPDA-II — Reduced Pressure Detector Assembly (ASSE 1047, fire service)
Air gap — physical separation, no assembly
● Premises isolation — at building water service entrance
○ In-plant isolation — at internal high-hazard cross-connection (boiler, chemical-feed, lab)
○ In-plant isolation — at internal low-hazard cross-connection (hose station, hydronic makeup)
○ Fire service supply
○ Irrigation supply
1/2 in.
3/4 in.
1 in.
1-1/4 in.
1-1/2 in.
2 in.
2-1/2 in.
3 in.
4 in.
6 in.
8 in.
10 in.
Per drawings
NOTE Higher-rated assemblies (RPZ above DCVA, for example) are always acceptable where a lower-rated assembly would be acceptable, but at additional first cost and pressure drop; the Engineer typically selects the lowest-cost compliant assembly at each location. (5.3.2)
6 Assembly Types
6.1 Reduced Pressure Principle Assembly (RPZ / RPA)
NOTE The reduced-pressure principle assembly — variously abbreviated RPZ (reduced-pressure-zone) or RPA (reduced-pressure assembly) — is the highest-rated mechanical backflow preventer and is the assembly required for all high-hazard cross-connections where an air gap is not used. (6.1.1)
NOTE The assembly consists of two independently-acting spring-loaded check valves with a hydraulically-controlled differential-pressure relief valve in the zone between them, plus two shut-off valves and four test cocks. (6.1.2)
NOTE Under normal flow, the upstream pressure exceeds the zone pressure by at least the differential established by the assembly (typically 3 to 10 psi); the relief valve remains closed. (6.1.3)
Bronze body, 1/2 in. through 2 in. (FNPT or threaded end connections)
Stainless steel body, 1/2 in. through 2 in.
Epoxy-coated cast iron body, 2-1/2 in. through 10 in. (flanged or grooved end connections)
Stainless steel body, 2-1/2 in. through 10 in.
☑ ASSE 1013
☐ AWWA C511
☐ USC FCCCHR approved-assemblies list
☐ CSA B64.4 (where Canadian compliance is required)
NOTE If the upstream pressure drops, the zone pressure approaches it and the relief valve opens, discharging the zone water to atmosphere through an air gap and interrupting any backflow path before contaminated water can cross both checks; if either check fouls or fails such that the zone pressure rises (a back-pressure event with a leaky first check), the relief valve opens and discharges the zone, again interrupting the backflow path. (6.1.4)
6.1.5 Every RPZ installation shall be provided with an indirect waste receptor (floor drain, hub drain, or similar) below the relief-valve discharge, sized to carry the worst-case relief-valve discharge rate without backing up into the relief port.
6.1.6 The relief port shall discharge through an air gap to the indirect waste receptor and shall not be hard-piped to the drainage system.
6.2 Double Check Valve Assembly (DCVA)
NOTE The double check valve assembly consists of two independently-acting spring-loaded check valves arranged in series, plus two shut-off valves and four test cocks. (6.2.1)
NOTE The DCVA does not have a relief valve and does not require an indirect waste receptor for discharge, simplifying the installation compared to an RPZ. (6.2.2)
Bronze body, 1/2 in. through 2 in. (FNPT or threaded end connections)
Stainless steel body, 1/2 in. through 2 in.
Epoxy-coated cast iron body, 2-1/2 in. through 10 in. (flanged or grooved end connections)
Stainless steel body, 2-1/2 in. through 10 in.
☑ ASSE 1015
☐ AWWA C510
☐ USC FCCCHR approved-assemblies list
☐ CSA B64.5 (where Canadian compliance is required)
6.2.3 The DCVA may be used for low-hazard cross-connections, including most premises-isolation installations on commercial buildings without high-hazard internal cross-connections, and for fire-service supply piping where the AHJ classifies the fire service as low-hazard (no antifreeze, no auxiliary supply).
6.2.4 The DCVA shall not be installed at any high-hazard cross-connection.
NOTE The two checks in a DCVA provide redundancy against a single-check failure, but if a contaminated downstream source forces both checks to leak — through fouling, deterioration, or simultaneous failure — there is no physical interruption of the flow path as there is in an RPZ; for this reason codes and water purveyors require the higher-rated RPZ at health-hazard connections. (6.2.5)
6.3 Pressure Vacuum Breaker (PVB)
NOTE The pressure vacuum breaker is a back-siphonage-only assembly used principally for irrigation supply and similar low-hazard, back-siphonage-only cross-connections. (6.3.1)
NOTE The assembly consists of a single spring-loaded check, a spring-loaded air-inlet valve, two shut-off valves, and two test cocks. (6.3.2)
NOTE Under positive pressure the air inlet is held closed; under negative supply pressure the air inlet opens and vents the assembly to atmosphere, interrupting any back-siphonage flow path. (6.3.3)
6.3.4 The PVB shall be installed not less than 12 inches above the highest downstream point of use (the highest sprinkler head, the highest hose-bib, the elevated tank inlet), as required by ASSE 1020.
6.3.5 The PVB shall not be used where back-pressure is possible.
6.3.6 Irrigation systems with a downstream booster pump shall use a DCVA or RPZ, with RPZ required for any chemical injection.
6.3.7 The PVB shall not be installed in a pit, vault, or below-grade location, because the air-inlet vent must discharge freely to atmosphere; submerged or partially-submerged PVB air-inlet ports cannot vent and may fail to actuate.
6.4 Spill-Resistant Vacuum Breaker (SVB)
NOTE The spill-resistant vacuum breaker is functionally similar to a PVB but is designed so that the air-inlet vent does not discharge water during normal operation, eliminating the "first-flush spill" that occurs in a standard PVB each time the assembly is pressurized after isolation. (6.4.1)
● Indoor low-hazard back-siphonage protection (laboratory, equipment branch, indoor irrigation manifold)
○ Replacement for PVB where first-flush spill is unacceptable
NOTE SVBs are appropriate for indoor installations where a PVB's first-flush discharge would be undesirable — laboratory benches, equipment supply branches, and indoor irrigation manifolds. (6.4.2)
6.4.3 Like the PVB, the SVB is back-siphonage-only and shall not be used where back-pressure is possible.
6.5 Atmospheric Vacuum Breaker (AVB)
NOTE The atmospheric vacuum breaker is the simplest and lowest-cost back-siphonage device. (6.5.1)
NOTE It consists of an air-inlet poppet that drops open under negative pressure to vent the downstream piping to atmosphere. (6.5.2)
NOTE AVBs have no internal check valve and no shut-off valves and are not field-testable. (6.5.3)
● Integral fixture protection (service sink, hose bibb, laboratory faucet — covered by [[sync/plumbing-fixtures]])
○ In-line AVB on irrigation manifold (no downstream shutoff within 12 hours of use)
6.5.4 The AVB shall not be used where any downstream isolation valve, solenoid, or shut-off can hold the assembly under continuous pressure for more than 12 hours.
NOTE Continuous pressure causes the AVB poppet to remain seated against its seal and increases the risk of failure under back-siphonage. (6.5.5)
NOTE AVBs are used principally as integral fixture protection — service-sink faucet AVBs, hose-thread AVBs at hose-bibs, and laboratory faucet vacuum breakers — and as in-line protection on irrigation manifolds with no downstream shut-off. (6.5.6)
6.5.7 The AVB shall be installed not less than 6 inches above the highest downstream point of use (the rim of the sink, the flood rim of the receptor, or the highest sprinkler head).
NOTE The dual-check valve with intermediate atmospheric vent assembly — sometimes abbreviated DCAP or referred to by the ASSE 1012 designation — is a residential and small-commercial assembly consisting of two checks in series with a small atmospheric vent in the zone between them. (6.6.1)
NOTE DCAP assemblies are typically supplied in 1/2 in. and 3/4 in. sizes and are not field-testable in the same manner as an RPZ. (6.6.2)
● Residential boiler makeup water
○ Residential softener or treatment-equipment bypass
○ Small low-hazard residential cross-connection where RPZ is not required by code
6.6.3 The DCAP may be used for low-to-moderate-hazard residential installations such as residential boiler makeup water, residential softener bypasses, and similar small-bore connections where the cost and footprint of a full RPZ are not justified.
6.6.4 DCAP assemblies shall not be substituted for an RPZ on any high-hazard or commercial-scale installation.
6.7 Double Check Detector Assembly — DCDA-II
NOTE The double check detector assembly (current generation, DCDA-II per ASSE 1048) is a DCVA configured for fire-service supply. (6.7.1)
NOTE It consists of a main-line DCVA in the fire-service supply, with a smaller parallel bypass line containing a meter and a second DCVA in series; the bypass detects small unauthorized flows (theft of water, unauthorized hose connections, undetected leaks) that would otherwise pass through the main-line checks without registering on the main meter. (6.7.2)
NOTE The DCDA-II is the standard fire-service backflow assembly for low-hazard fire services — fire sprinkler systems with no antifreeze, no auxiliary water source, and no chemical foam connection. (6.7.3)
☑ ASSE 1048
☐ USC FCCCHR approved-assemblies list (fire protection)
☐ UL/FM listed for fire service
6.7.4 Coordinate DCDA-II selection with the fire protection scope (Wet Pipe Fire Sprinkler Systems) and confirm that the assembly's pressure drop at the fire-flow demand has been accounted for in the hydraulic calculation. NOTE Fire-service backflow assemblies introduce significant pressure loss at the fire-flow demand and may require a larger upstream supply size or a fire pump to satisfy the sprinkler system demand. (6.7.5)
6.8 Reduced Pressure Detector Assembly — RPDA-II
NOTE The reduced pressure detector assembly (current generation, RPDA-II per ASSE 1047) is the fire-service equivalent of the RPZ — required where the fire sprinkler system is classified as high-hazard. (6.8.1)
NOTE Like the RPDA, the RPDA-II configuration includes the smaller bypass detector line. (6.8.2)
☑ ASSE 1047
☐ USC FCCCHR approved-assemblies list (fire protection)
☐ UL/FM listed for fire service
NOTE High-hazard fire-service classifications typically apply when the sprinkler system contains antifreeze (a potential health hazard if drawn back into the potable supply), has an auxiliary water source (atmospheric storage tank, gravity tank, river, pond), accepts foam concentrate injection (foam-water sprinkler systems), or is otherwise classified as high-hazard by the AHJ or water purveyor. (6.8.3)
6.8.4 Because the RPDA-II has a relief-valve discharge in the main line, the installation shall include an indirect-waste receptor sized for the relief-valve worst-case discharge rate, which can be substantial in large-diameter fire-service assemblies.
6.8.5 Coordinate the discharge floor drain, hub drain, or vault sump with the architectural and civil drawings.
7 Test Port (Test Cock) Arrangement
NOTE ASSE 1013, 1015, 1020, 1056, 1047, and 1048 assemblies are equipped with test cocks (test ports) that allow field testing of the assembly using a differential-pressure test gauge. (7.1)
NOTE The number and location of test cocks varies by assembly type — RPZs and DCVAs have four test cocks (one upstream, one in the zone between checks, one between the second check and the downstream shut-off, and one downstream of the downstream shut-off, configured per the assembly manufacturer's published test procedure). (7.2)
NOTE PVBs and SVBs have two test cocks. (7.3)
● Four test cocks for RPZ / RPDA-II / DCVA / DCDA-II (factory equipped)
○ Two test cocks for PVB / SVB (factory equipped)
7.4 Test cocks shall be the manufacturer's supplied ball-valve type with a hose-thread or compression fitting and shall not be substituted, plugged, or removed.
8 Certifying Body
NOTE The certifying body that lists the assembly determines which approved-assemblies list it can appear on and which markets it can be sold into. (8.1)
☑ ASSE International (ASSE 1013, 1015, 1020, 1056, 1012, 1001, 1011, 1047, 1048 as applicable)
☐ USC FCCCHR (Foundation for Cross-Connection Control and Hydraulic Research, USC)
☐ AWWA C510 / C511 (where waterworks-grade certification is required)
☐ CSA B64 series (Canadian compliance)
☐ UL / FM (fire-service assemblies)
NOTE ASSE International maintains the principal US listing program; AWWA C-series standards apply specifically to DCVA (C510) and RPZ (C511) assemblies for waterworks service; the USC FCCCHR maintains a separate testing and approval program whose list is the primary or sole acceptance list for many US water purveyors; CSA B64 is the Canadian equivalent. Most production assemblies are listed by multiple bodies — ASSE plus USC FCCCHR is the typical US baseline, and AWWA plus ASSE plus USC FCCCHR is the baseline for waterworks-grade large-bore assemblies. (8.2)
9 Installation
9.1 Orientation
Horizontal — assembly axis level, test cocks accessible
Vertical, flow upward (PVB / SVB — required; certain N-pattern RPZ / DCVA only)
Vertical, flow downward (certain N-pattern RPZ / DCVA only — confirm USC approval)
9.1.1 Each assembly shall be installed in the orientation listed by the certifying body for that assembly.
NOTE Most RPZs and DCVAs in sizes 2 inches and smaller are listed for horizontal installation only; some current-generation N-pattern and Y-pattern assemblies are listed for horizontal, vertical (flow up), or vertical (flow down) installation, and PVBs and SVBs are listed for vertical (flow up) installation with the air-inlet vent in the upward orientation. (9.1.2)
9.1.3 The Contractor shall verify the listed orientations on the specific model's USC FCCCHR approval before installing in any orientation other than horizontal.
9.2 Clearance for Testing and Service
9.2.1 Each assembly shall be installed with clearance on all sides sufficient to permit field testing, parts replacement, and inspection.
NOTE Recommended minimum clearances per USC FCCCHR and AWWA Manual M14 are: 12 inches above the assembly to the ceiling, soffit, or structure; 12 inches below the assembly to the floor or housekeeping pad (24 inches recommended for assemblies 2-1/2 inches and larger to permit relief-valve service and indirect-waste-receptor visibility); 12 inches on each side; and 24 inches in front of the assembly for tester access. (9.2.2)
☑ 12 in. minimum above the assembly (ceiling / soffit / structure)
☐ 12 in. minimum below the assembly (floor / housekeeping pad)
☐ 24 in. minimum below for 2-1/2 in. and larger (relief valve and drain visibility)
☐ 12 in. minimum on each side
☐ 24 in. minimum in front for tester access
☐ Assembly is reachable without ladder, contortion, or removal of adjacent equipment
9.2.3 The assembly shall not be installed in a location that requires a ladder, contortion, or removal of adjacent equipment to access the test cocks or the relief valve.
9.3 Installation Height — Backflow Prevention Assemblies
9.3.1 RPZ and DCVA assemblies shall be installed at a height between 12 inches and 60 inches above the finished floor (measured to the bottom of the assembly body), per USC FCCCHR.
1260
122430364860
Default: 36 in
NOTE Assemblies installed lower than 12 inches above the finished floor cannot be tested or serviced without flooding the floor with the discharge from a test cock and cannot be inspected from a standing position, while assemblies installed higher than 60 inches place test cocks beyond comfortable reach and create a fall hazard during testing. (9.3.2)
9.4 Indirect Waste — RPZ and RPDA-II Relief Discharge
NOTE The indirect waste receptor for the relief discharge of every RPZ and RPDA-II assembly is governed by the following requirements. (9.4.1)
Floor drain with trap and vent, sized for worst-case relief discharge
Hub drain with trap and vent, sized for worst-case relief discharge
Floor sink with trap and vent, sized for worst-case relief discharge
Trench drain (for large fire-service RPDA-II only)
● Worst-case relief-valve discharge rate per manufacturer's published curve
○ Sized per [[sync/sanitary-waste-and-vent-piping]] indirect waste sizing
9.4.2 The relief valve discharge of every RPZ and RPDA-II assembly shall discharge through an air gap (minimum air gap equal to twice the diameter of the relief port, but in no case less than 1 inch) to a properly sized indirect waste receptor.
9.4.3 The receptor shall be a floor drain, hub drain, or floor sink connected to the building's drainage system through a trap and vent per Sanitary Waste And Vent Piping. 9.4.4 The relief discharge shall not be hard-piped to the drainage system or to any other discharge point that could be submerged, restricted, or pressurized.
9.4.5 The indirect waste receptor shall be sized for the worst-case relief-valve discharge rate.
NOTE Manufacturer-published discharge curves give the maximum flow at the differential at which the relief valve fully opens — typically several gpm for residential and small-commercial RPZs (3/4 in., 1 in.), tens of gpm for medium-bore commercial RPZs (1-1/2 in., 2 in.), and hundreds of gpm for large fire-service and industrial RPDA-II assemblies (4 in., 6 in., 8 in., 10 in.); undersized receptors back up during a relief-discharge event, flood the surrounding area, and may trip below-grade water sensors. (9.4.6)
9.4.7 The Contractor shall confirm the receptor's drain capacity (the connected drainage piping and trap size) against the worst-case relief-discharge rate.
9.5 Drain Pan or Drain Lines Are Not Substitutes
9.5.1 A drain pan or a hose-trapped drain line shall not be used as a substitute for an indirect waste receptor with an air gap.
NOTE Relief valves can discharge at high flow rates and the pressurized discharge will overwhelm a small pan; a hose-trapped line creates a back-pressure path that prevents the relief valve from fully opening, defeating the assembly's backflow protection. (9.5.2)
9.5.3 The relief discharge shall be vertical and unrestricted to the indirect-waste air gap.
9.6 Supports
Supported by connected piping (assemblies 2 in. and smaller, piping supported within 6 in. of each end)
Dedicated floor stand
Dedicated hanger from structure
Wall-mounted bracket
Mounted on packaged skid
9.6.1 Each assembly shall be supported independently of the connected piping.
9.6.2 Assemblies 2 inches and smaller may be supported by the connected piping if the connected piping is itself supported within 6 inches of each assembly end-connection.
9.6.3 Assemblies 2-1/2 inches and larger shall be supported by a dedicated stand, hanger, or wall-mounted bracket sized for the assembly weight plus the weight of water in the assembly plus a dynamic factor.
9.6.4 The significant weight of assemblies 6 inches and larger shall not be transferred to the connected piping.
9.6.5 Seismic restraint shall be provided per Domestic Water Piping where the project Seismic Design Category requires it. 9.7 Shut-Off Valves and Strainer
NOTE Each RPZ, DCVA, DCDA-II, RPDA-II, PVB, and SVB assembly is factory-equipped with upstream and downstream shut-off valves of the resilient-seated, full-port type. (9.7.1)
● Yes — wye-strainer with blowdown valve upstream of assembly
○ No — assembly inlet not protected by separate strainer
9.7.2 The Contractor shall not substitute, modify, or remove the factory-equipped shut-off valves.
9.7.3 A strainer or wye-strainer may be installed upstream of the assembly to protect the checks and the relief valve from debris that could foul the seats.
NOTE Strainers are recommended on new-construction installations and on installations downstream of water main work where construction debris is likely. (9.7.4)
9.7.5 The strainer shall include a blowdown valve for periodic cleaning and shall be installed between the upstream isolation valve (separate from the assembly's integral shut-off) and the assembly inlet.
9.8 Bypass Provisions
○ Yes — parallel bypass with second assembly of equal rating (critical loads)
● No — service interruption acceptable during annual testing
9.8.1 Where uninterrupted water service must be maintained during periodic backflow assembly testing and repair — typically at healthcare facilities, critical industrial process loads, and certain commercial occupancies — a parallel bypass with a second assembly of equal or higher rating may be provided.
9.8.2 The bypass shall be valved and shall be controlled by the Owner's procedures during testing.
NOTE Where a parallel bypass is not provided (the typical configuration), the Owner must accept water-service interruption during annual testing; testing typically takes 30 to 60 minutes per assembly. (9.8.3)
10 Freeze Protection and Outdoor Installation
10.1 Indoor Installation Preferred
NOTE Backflow prevention assemblies are best installed indoors in a heated mechanical space, because the internal mechanism — spring-loaded checks, relief valve diaphragms, air-inlet poppets — is damaged by freezing, and damage from a single freeze event is rarely repairable in place; the assembly typically must be replaced. (10.1.1)
10.1.2 Where the building configuration permits, the Engineer shall locate the premises-isolation assembly inside the building, downstream of the meter and the building main shut-off, in a heated mechanical or utility space.
10.2 Outdoor or Unconditioned Space — Heated Enclosure Required
10.2.1 Where assemblies must be installed outdoors or in unconditioned spaces in regions subject to freezing, a heated enclosure ("hot box") is required, governed by the following.
Heated enclosure (hot box) with thermostat, electric heat, insulation, and lock
Below-grade vault with insulation and drainage (for large fire-service assemblies)
Not applicable — installed indoors in heated space
Not applicable — installed in climate not subject to freezing
3560
3540455060
Default: 40 °F
1002400
10020040080015002400
Default: 400 W
Per drawings
10.2.2 Where assemblies must be installed outdoors or in unconditioned spaces in regions subject to freezing, a heated enclosure ("hot box") shall be provided.
10.2.3 The enclosure shall include continuous thermostatically-controlled electric resistance heat, insulation rated for the regional design low temperature, an interior thermostat set above freezing (typically 40°F minimum), drain provisions for the relief-valve discharge to an exterior splash pad or to a daylight discharge above grade through an unrestricted vertical pipe, lockable access doors for AHJ and tester access, and ventilation appropriate to the heater type.
10.2.4 The enclosure shall be sized for the assembly footprint plus the required test, service, and clearance space, and shall be installed on a concrete pad with the assembly elevated sufficiently above the pad for testing.
10.3 Below-Grade Vaults
10.3.1 Where below-grade vault installation is unavoidable (typically for large fire-service DCDA-II / RPDA-II assemblies at the property line), the vault shall include positive drainage to a daylight discharge or to a sump with a duplex pump system sized to maintain the vault free of water under the worst-case relief-valve discharge, an unconditioned ventilation provision sized to prevent condensation accumulation, a confined-space-rated access hatch, and freeze protection where the regional design low temperature can drive vault temperatures below freezing despite the soil thermal buffer.
10.3.2 Vaults shall not be used for PVB or SVB assemblies, because the air-inlet vent of these assemblies requires free atmospheric venting and shall not be installed in a confined space.
11 Testing and Commissioning
11.1 Initial Commissioning Test
NOTE The initial commissioning test verifies that the assembly was not damaged in shipping or installation, that the checks hold the rated differential pressure, that the relief valve opens at the rated differential (RPZ and RPDA-II only), that the air-inlet valve operates (PVB and SVB only), and that there are no leaks in the assembly or in the shut-off valves. (11.1.1)
● ASSE 5110 (or state equivalent) certified tester engaged by the Contractor
○ ASSE 5110 (or state equivalent) certified tester engaged directly by the Owner
○ Water purveyor's cross-connection control program tester
11.1.2 Every backflow prevention assembly installed under this scope shall be commissioned by a certified tester before the assembly is placed in service.
11.1.3 The commissioning test shall be performed using a calibrated differential-pressure test gauge per the manufacturer's published procedure and the AWWA Manual M14 procedure.
11.2 Test Report
11.2.1 The test report shall be on the form required by the water purveyor or the AHJ.
11.2.2 At minimum, the test report shall identify the property and assembly location, the assembly type and manufacturer, the model number and serial number, the size, the installation date, the test date, the tester's name, the tester's certification number and expiration, the test-gauge calibration certificate number and calibration date, the recorded pressure values for each check (DCVA and RPZ) or the relief opening differential (RPZ), the recorded air-inlet opening pressure (PVB and SVB), the pass/fail determination for each test step, and the tester's signature.
11.3 Submission and Tagging
11.3.1 The initial commissioning test report shall be submitted to the water purveyor and the AHJ on the schedule required by their cross-connection control programs (typically within 10 to 30 days of installation).
11.3.2 Each assembly shall be tagged at installation with a permanent, weather-resistant tag identifying the assembly type, size, serial number, installation date, and next required test date.
11.3.3 The tag shall remain affixed to the assembly throughout its service life; subsequent annual test reports are tracked by the assembly's unique identifier.
11.4 Annual Recertification
☑ Permanent weather-resistant tag affixed to assembly
☐ Tag identifies assembly type, size, serial number, installation date
☐ Tag identifies next required test date (12 months from commissioning)
☐ Tag includes water purveyor's program identifier (if required)
11.4.1 After initial commissioning, every testable backflow prevention assembly shall be retested at least annually by a certified tester.
NOTE The annual retest is the responsibility of the Owner, not the Contractor (unless extended by warranty or service contract), and is not within the scope of this construction standard; water purveyors enforce annual retest requirements and may discontinue service to a property whose assembly is not retested on schedule. (11.4.2)
11.4.3 The Contractor shall provide tagging and documentation that enables the Owner's facility management to schedule the annual retest.
11.5 Pressure Drop Verification
11.5.1 Where the assembly's pressure drop affects the downstream system's hydraulic performance — fire sprinkler systems, fire pumps, irrigation systems with marginal supply pressure — the Contractor shall verify the pressure drop at the design flow rate during commissioning.
11.5.2 The verified pressure drop shall be recorded in the commissioning report and compared against the design assumptions.
11.5.3 Significant deviation (greater than 5 percent above the design value) may indicate fouling, internal damage, or an incorrect assembly size and shall be reported to the Engineer for resolution.
12 Installation Coordination
12.1 Service Entrance Configuration
NOTE At the building water service entrance, the typical configuration is: water service from utility — water meter — building main shut-off — strainer (optional) — premises-isolation backflow assembly — indirect waste receptor below RPZ relief — downstream distribution. (12.1.1)
NOTE The premises-isolation assembly is typically the first piece of equipment downstream of the meter and main shut-off, providing immediate isolation of the building from the public main. (12.1.2)
12.2 Fire Service Configuration
NOTE At the fire service entrance, the typical configuration is: fire service from utility — meter (where required, often a detector check meter integral to the DCDA-II / RPDA-II) — fire-service backflow assembly (DCDA-II or RPDA-II) — fire department connection (FDC) and post-indicator valve as required by NFPA 24 — riser to sprinkler system. (12.2.1)
NOTE The fire-service backflow assembly is typically installed immediately downstream of the property-line vault or the fire-service entrance. (12.2.2)
● Inside building at fire service entrance
○ Below-grade vault at property line
○ Heated enclosure on exterior pad at building
12.3 Internal Cross-Connection Inventory
12.3.1 The Engineer shall inventory every internal cross-connection on the project and specify in-plant backflow protection at each.
NOTE Typical internal high-hazard cross-connections in commercial buildings include: boiler makeup water (high-hazard due to boiler water treatment chemicals); chilled-water and hydronic-loop makeup water (high-hazard if glycol or water treatment is used; low-hazard otherwise); cooling-tower makeup water (high-hazard due to biocide treatment); laboratory and healthcare equipment with potable water connections (high-hazard); kitchen equipment with potable connections in food service (varies by equipment); irrigation supply (high-hazard if any fertilizer or pesticide injection, low-hazard if none); and dedicated hose-bib stations in mechanical rooms and industrial spaces (varies by use). (12.3.2)
☑ Boiler makeup water — RPZ (chemical treatment hazard)
☐ Hydronic makeup water — RPZ (where glycol or chemicals present)
☐ Hydronic makeup water — DCVA (no chemicals, water-only system)
☐ Cooling-tower makeup — RPZ
☐ Irrigation supply (with injection) — RPZ
☐ Irrigation supply (no injection) — PVB or DCVA
☐ Laboratory equipment connections — RPZ
☐ Kitchen / food-service equipment — per equipment listing
☐ Hose-bib stations — fixture-integral AVB (covered by [[sync/plumbing-fixtures]])
13 Pressure and Hydraulic Considerations
13.1 Pressure Drop
NOTE Every mechanical backflow prevention assembly introduces a pressure drop in the supply line — the differential pressure across the checks plus the friction loss through the assembly body and end-connections. (13.1.1)
NOTE Typical pressure drops range from approximately 5 psi for small DCVAs at moderate flow to 12 psi or more for large RPZs at peak flow. (13.1.2)
13.1.3 The Engineer shall account for the assembly pressure drop in the building's hydraulic calculation.
NOTE Where the upstream supply pressure is marginal — at the end of long distribution mains, at high elevations on multi-story buildings, or at sites where the water purveyor's minimum residual pressure is at the lower end of the acceptable range — the assembly's pressure drop can drop downstream pressure below the minimum required for fixture operation or for fire sprinkler design. (13.1.4)
13.2 Closed-System Behavior
NOTE A backflow assembly with check valves at the building service entrance creates a closed system on the downstream (building) side — water that expands when heated has no relief path back to the utility main. (13.2.1)
NOTE This causes thermal expansion to drive pressure spikes in the building's hot-water system, which can damage fixtures, water heaters, and other equipment, and can open relief valves. (13.2.2)
● Yes — required because building service entrance includes a backflow assembly
○ No — only where the system is verified to remain open (rare in commercial)
13.2.3 The Engineer shall specify a thermal expansion tank on the cold-water side of every water heater (or at the building service downstream of the backflow assembly) per Water Heaters and per the applicable plumbing code. 13.3 Pressure Reducing Valve Coordination
13.3.1 Where building service pressure exceeds 80 psi at the service entrance and a pressure reducing valve (PRV) is required per Domestic Water Piping, the PRV shall be installed downstream of the backflow assembly (and downstream of the thermal expansion tank, where one is provided on the cold side). NOTE Installing the PRV upstream of the backflow assembly exposes the assembly to potentially higher service pressure and can disturb the relief valve's differential reference; downstream installation isolates the building distribution from the supply. (13.3.2)
14 Delivery, Storage, and Handling
14.1 Backflow prevention assemblies shall be delivered in their original protective packaging with end-connection covers in place.
14.2 Assemblies shall be stored in a dry, climate-controlled location, out of direct sunlight and away from welding, painting, or solvent application that could contaminate elastomer seals.
14.3 End-connection covers shall remain in place until immediately before installation.
14.4 The Contractor shall not store assemblies on the ground, on bare concrete, or in any location where moisture, debris, or contamination could enter through the end connections.
14.5 Assemblies that have been on site for more than 90 days before installation shall be inspected before installation.
NOTE Check disc elastomers can develop a "set" from sustained spring load during long storage with the assembly oriented horizontally. (14.6)
14.7 The manufacturer's published recommendations for stored-assembly inspection or refurbishment before installation shall be followed.
15 Warranty
15.1 The Contractor shall warrant each installed backflow prevention assembly against defects in installation and workmanship for a period of one year from substantial completion.
NOTE The manufacturer's product warranty (typically one to two years for assemblies, with longer warranties on the body casting and shorter coverage on elastomer components) is in addition to the Contractor's installation warranty. (15.2)
15.3 The Contractor's warranty does not cover damage caused by freezing where the freeze protection was installed and operating per the contract documents, damage from contamination introduced by Owner operations after substantial completion, or normal wear of elastomer components.
15.4 If an assembly fails its annual recertification test within the warranty period and the failure is attributable to installation or workmanship (rather than to normal wear, freeze damage, contamination, or Owner-caused conditions), the Contractor shall repair or replace the assembly at no cost to the Owner.
15.5 The Contractor shall retest the repaired or replaced assembly using a certified tester and submit the resulting test report to the water purveyor and the AHJ.
16 Spare Parts
16.1 The Contractor shall deliver to the Owner at substantial completion a spare parts inventory sized for the assemblies installed on the project.
16.2 The inventory shall include at minimum, for each model and size installed:
- One complete check valve rebuild kit (springs, seats, discs, O-rings) for the first check
- One complete check valve rebuild kit for the second check
- One relief valve rebuild kit (RPZ and RPDA-II only)
- One air-inlet valve rebuild kit (PVB and SVB only)
- The manufacturer's special tools required for in-place rebuild (where the rebuild requires non-standard tools)
☑ First check rebuild kit (springs, seats, discs, O-rings)
☐ Second check rebuild kit
☐ Relief valve rebuild kit (RPZ / RPDA-II)
☐ Air-inlet valve rebuild kit (PVB / SVB)
☐ Special tools for in-place rebuild
☐ Test cock replacement set
16.3 Spare parts shall be delivered in the manufacturer's original sealed packaging with the part numbers, the compatible model numbers, and the date of manufacture clearly marked.
16.4 Spare parts that exceed their shelf life at delivery (typically two years for elastomer-containing kits, indefinite for metal-only parts) shall not be accepted by the Owner.