Backflow Prevention
Remade from scratch to the authoring rules: defaults asserted only where four of five projects would choose them, and scope boundaries matched to the neighboring standards
Showing changes from Rev 5
to Rev 6
in Backflow Prevention.
−---
−title: Backflow Prevention
−category: Plumbing
−toc_depth: 3
−description: >
− When to use: Backflow prevention assemblies and cross-connection control for potable water systems in commercial, institutional, and industrial buildings. Covers the selection, installation, testing, certification, and freeze protection of reduced-pressure principle assemblies (RPZ/RPA), double-check valve assemblies (DCVA), pressure vacuum breakers (PVB), spill-resistant vacuum breakers (SVB), atmospheric vacuum breakers (AVB), and dual-check valves with intermediate atmospheric vent (DCAP), as well as fire-service detector check assemblies (DCDA-II and RPDA-II). Includes selection by degree of hazard and type of cross-connection, indirect-waste sizing for RPZ discharge, heated-enclosure requirements for outdoor installations, and annual certification by qualified testers.
−
− Not intended for: Fixture-integral vacuum breakers and atmospheric vacuum breakers that are an integral part of a listed plumbing fixture or fitting (covered by the fixture or fitting standard, such as a service-sink faucet's integral vacuum breaker — see [[sync/plumbing-fixtures]]); non-potable reuse, greywater, rainwater harvesting, and reclaimed water systems (separate scope); irrigation backflow assemblies that are part of the landscape irrigation scope (separate scope) — though the assembly types and testing requirements in this standard apply; chemical-feed and process backflow protection in industrial settings beyond the building potable water boundary; the fire protection sprinkler system downstream of the fire-service backflow preventer (see [[sync/wet-pipe-fire-sprinkler-systems]]); hydronic system makeup-water backflow protection that is integral to a packaged hydronic skid (see [[sync/hydronic-piping]]); medical gas and vacuum systems; and water utility backflow assemblies upstream of the building water service entrance, which are governed by the water purveyor's cross-connection control program.
−---
−
−# Scope {toc}
−
−## 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. {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. {note}
−
−## Assembly locations, applications, and sizes are [[drawing: as indicated on the plumbing floor plans, plumbing riser diagrams, and backflow assembly schedule]]. {note}
−## This standard establishes the material, performance, installation, freeze-protection, and testing requirements that govern those drawings. {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. {note}
−
−## 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.
−
−## 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.
−
−## Coordination {toc}
−
−### Coordinate domestic-water-side piping, isolation valves, and pressure conditions with [[sync/domestic-water-piping]].
−
−### Coordinate fire-service backflow assembly selection and detector check sizing with [[sync/wet-pipe-fire-sprinkler-systems]] and with NFPA 13.
−
−### Coordinate water-heater expansion control with [[sync/water-heaters]].
−
−### Coordinate hydronic system makeup-water backflow protection with [[sync/hydronic-piping]].
−
−### 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 [[sync/plumbing-fixtures]] and is outside the scope of this standard. {note}
−
−# Referenced Standards {toc}
−
−## 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) |
−
−## 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.
−
−## 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.
−
−# Submittals {toc}
−
−## Action Submittals {toc}
−
−### 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
−
−```datasheet
−label: Action Submittals Required
−type: checkbox
−options:
− - "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"
−default: "Backflow assembly product data with ASSE listing and USC FCCCHR approval"
−```
−
−### Work shall not proceed on any backflow assembly installation until the corresponding submittals have been reviewed and returned.
−
−### Where the water purveyor maintains an approved-assemblies list, the submitted assemblies shall appear on that list for the assembly type and size specified.
−
−## Closeout Submittals {toc}
−
−### 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
−
−```datasheet
−label: Closeout Submittals Required
−type: checkbox
−options:
− - "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"
−default: [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]
−```
−
−# Quality Assurance {toc}
−
−## Installer Qualifications {toc}
−
−### 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.
−
−### The Contractor's license shall be current and shall cover the full scope of work.
−
−### Where the water purveyor or AHJ requires individual installer certification or registration in a backflow prevention installer program, personnel shall hold current qualifying credentials.
−
−## Tester Qualifications {toc}
−
−### 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. {note}
−
−### 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.
−
−```datasheet
−label: Tester Certification Required
−type: select
−options:
− - "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"
−default: "Any of the above accepted by the AHJ and water purveyor"
−```
−
−### The tester's credentials shall be current at the time of testing — an expired credential invalidates the test.
−
−## Test-Equipment Calibration {toc}
−
−### 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).
−
−### A current calibration certificate shall be available at the test site for review by the AHJ inspector.
−
−### Test reports shall reference the calibration certificate number.
−
−## Lead-Free Compliance {toc}
−
−### 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.
−
−### 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. {note}
−
−### 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.
−
−## Water Purveyor Approval {toc}
−
−### 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).
−
−### In most US jurisdictions the approved-assemblies list is the USC FCCCHR approved-assemblies list; some states maintain their own additional lists. {note}
−
−### The Contractor shall confirm each proposed assembly's approval status before procurement.
−
−### Assemblies not on the applicable approved list shall not be installed even when they are listed by other certifying bodies.
−
−## Regulatory Inspection {toc}
−
−### Each backflow prevention assembly installation shall be available for inspection by the AHJ and by the water purveyor's cross-connection control inspector.
−
−### 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.
−
−### 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.
−
−# Selection of Assembly Type {toc}
−
−## Degree of Hazard {toc}
−
−### Cross-connections are classified by the degree of hazard the non-potable source represents to the public health. {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. {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. {note}
−
−### High-hazard cross-connections shall be protected by either a reduced-pressure principle assembly (RPZ/RPA) or an air gap.
−
−### Low-hazard cross-connections may be protected by a double-check valve assembly (DCVA), a pressure vacuum breaker (PVB), or a higher-rated device.
−
−### 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.
−
−```datasheet
−label: Degree of Hazard at Cross-Connection
−type: radio
−options:
− - "High-hazard (health-hazard) — RPZ, RPDA-II, or air gap required"
− - "Low-hazard (non-health-hazard / pollution) — DCVA, DCDA-II, PVB, or higher acceptable"
−default: "High-hazard (health-hazard) — RPZ, RPDA-II, or air gap required"
−```
−
−## Type of Backflow {toc}
−
−### The type of backflow possible at a cross-connection determines which assembly types are acceptable, independent of the degree of hazard. {note}
−
−### The type of backflow possible at each cross-connection — back-siphonage only or back-pressure — shall be determined and specified.
−
−```datasheet
−label: Type of Backflow Possible at Cross-Connection
−type: radio
−options:
− - "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)"
−default: "Back-pressure possible (booster pump, boiler, elevated tank, chemical injection, or other pressurized downstream source)"
−```
−
−### 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. {note}
−
−### 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.
−
−### 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). {note}
−
−### 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.
−
−## Assembly Selection Matrix {toc}
−
−### The following matrix summarizes acceptable assemblies for combinations of hazard and backflow type. {note}
−
−| 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) |
−
−### The backflow prevention assembly type shall be specified for each cross-connection, consistent with the degree of hazard and the type of backflow possible.
−
−```datasheet
−label: Assembly Type Selected
−type: select
−options:
− - "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"
−default: "RPZ — Reduced Pressure Principle Assembly (ASSE 1013)"
−```
−
−### The application of each backflow assembly — premises isolation, in-plant isolation, fire service, or irrigation — shall be specified.
−
−```datasheet
−label: Application
−type: radio
−options:
− - "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"
−default: "Premises isolation — at building water service entrance"
−```
−
−### The service line size at each backflow assembly location shall be specified.
−
−```datasheet
−label: Service Line Size
−type: select
−unit: in
−drawing_ref: true
−options:
− - "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."
−default: "2 in."
−```
−
−### 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. {note}
−
−# Assembly Types {toc}
−
−## Reduced Pressure Principle Assembly (RPZ / RPA) {toc}
−
−### 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. {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. {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. {note}
−
−### The RPZ body material and end-connection configuration shall be specified, consistent with the service line size at the installation.
−
−```datasheet
−label: RPZ Body Material and Configuration
−type: select
−options:
− - "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."
−default: "Bronze body, 1/2 in. through 2 in. (FNPT or threaded end connections)"
−```
−
−### The listing standards required for the RPZ assembly shall be specified for this installation.
−
−```datasheet
−label: RPZ Listing Standards
−type: checkbox
−options:
− - "ASSE 1013"
− - "AWWA C511"
− - "USC FCCCHR approved-assemblies list"
− - "CSA B64.4 (where Canadian compliance is required)"
−default: "ASSE 1013"
−```
−
−### 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. {note}
−
−### 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.
−
−### The relief port shall discharge through an air gap to the indirect waste receptor and shall not be hard-piped to the drainage system.
−
−## Double Check Valve Assembly (DCVA) {toc}
−
−### 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. {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. {note}
−
−### The DCVA body material and end-connection configuration shall be specified, consistent with the service line size at the installation.
−
−```datasheet
−label: DCVA Body Material and Configuration
−type: select
−options:
− - "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."
−default: "Epoxy-coated cast iron body, 2-1/2 in. through 10 in. (flanged or grooved end connections)"
−```
−
−### The listing standards required for the DCVA assembly shall be specified for this installation.
−
−```datasheet
−label: DCVA Listing Standards
−type: checkbox
−options:
− - "ASSE 1015"
− - "AWWA C510"
− - "USC FCCCHR approved-assemblies list"
− - "CSA B64.5 (where Canadian compliance is required)"
−default: "ASSE 1015"
−```
−
−### 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).
−
−### The DCVA shall not be installed at any high-hazard cross-connection.
−
−### 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. {note}
−
−## Pressure Vacuum Breaker (PVB) {toc}
−
−### The pressure vacuum breaker is a back-siphonage-only assembly used principally for irrigation supply and similar low-hazard, back-siphonage-only cross-connections. {note}
−### The assembly consists of a single spring-loaded check, a spring-loaded air-inlet valve, two shut-off valves, and two test cocks. {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. {note}
−
−### 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.
−
−```datasheet
−label: PVB Installation Elevation
−type: range
−unit: in
−options:
− min: 12
− max: 60
− step: 1
−default: 12
−```
−
−### The PVB shall not be used where back-pressure is possible.
−
−### Irrigation systems with a downstream booster pump shall use a DCVA or RPZ, with RPZ required for any chemical injection.
−
−### 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.
−
−## Spill-Resistant Vacuum Breaker (SVB) {toc}
−
−### 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. {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. {note}
−
−### Like the PVB, the SVB is back-siphonage-only and shall not be used where back-pressure is possible.
−
−```datasheet
−label: SVB Application
−type: radio
−options:
− - "Indoor low-hazard back-siphonage protection (laboratory, equipment branch, indoor irrigation manifold)"
− - "Replacement for PVB where first-flush spill is unacceptable"
−default: "Indoor low-hazard back-siphonage protection (laboratory, equipment branch, indoor irrigation manifold)"
−```
−
−## Atmospheric Vacuum Breaker (AVB) {toc}
−
−### The atmospheric vacuum breaker is the simplest and lowest-cost back-siphonage device. {note}
−### It consists of an air-inlet poppet that drops open under negative pressure to vent the downstream piping to atmosphere. {note}
−### AVBs have no internal check valve and no shut-off valves and are not field-testable. {note}
−
−### 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.
−
−```datasheet
−label: AVB Application
−type: radio
−options:
− - "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)"
−default: "Integral fixture protection (service sink, hose bibb, laboratory faucet — covered by [[sync/plumbing-fixtures]])"
−```
−
−### Continuous pressure causes the AVB poppet to remain seated against its seal and increases the risk of failure under back-siphonage. {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. {note}
−
−### 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).
−
−```datasheet
−label: AVB Installation Elevation Above Highest Point of Use
−type: range
−unit: in
−options:
− min: 6
− max: 60
− step: 1
−default: 6
−```
−
−## Dual-Check with Intermediate Atmospheric Vent (DCAP) {toc}
−
−### 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. {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. {note}
−
−### 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.
−
−```datasheet
−label: DCAP Application
−type: radio
−options:
− - "Residential boiler makeup water"
− - "Residential softener or treatment-equipment bypass"
− - "Small low-hazard residential cross-connection where RPZ is not required by code"
−default: "Residential boiler makeup water"
−```
−
−### DCAP assemblies shall not be substituted for an RPZ on any high-hazard or commercial-scale installation.
−
−## Double Check Detector Assembly — DCDA-II {toc}
−
−### The double check detector assembly (current generation, DCDA-II per ASSE 1048) is a DCVA configured for fire-service supply. {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. {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. {note}
−
−### The listing standards required for the DCDA-II assembly shall be specified, consistent with the fire service classification.
−
−```datasheet
−label: DCDA-II Listing
−type: checkbox
−options:
− - "ASSE 1048"
− - "USC FCCCHR approved-assemblies list (fire protection)"
− - "UL/FM listed for fire service"
−default: "ASSE 1048"
−```
−
−### Coordinate DCDA-II selection with the fire protection scope ([[sync/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.
−
−### 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. {note}
−
−## Reduced Pressure Detector Assembly — RPDA-II {toc}
−
−### 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. {note}
−### Like the RPDA, the RPDA-II configuration includes the smaller bypass detector line. {note}
−
−### The listing standards required for the RPDA-II assembly shall be specified, consistent with the fire service classification.
−
−```datasheet
−label: RPDA-II Listing
−type: checkbox
−options:
− - "ASSE 1047"
− - "USC FCCCHR approved-assemblies list (fire protection)"
− - "UL/FM listed for fire service"
−default: "ASSE 1047"
−```
−
−### 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. {note}
−
−### 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.
−
−### Coordinate the discharge floor drain, hub drain, or vault sump with the architectural and civil drawings.
−
−# Test Port (Test Cock) Arrangement {toc}
−
−## 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. {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). {note}
−## PVBs and SVBs have two test cocks. {note}
−
−## 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.
−
−```datasheet
−label: Test Cock Configuration (assembly manufacturer supplied)
−type: radio
−options:
− - "Four test cocks for RPZ / RPDA-II / DCVA / DCDA-II (factory equipped)"
− - "Two test cocks for PVB / SVB (factory equipped)"
−default: "Four test cocks for RPZ / RPDA-II / DCVA / DCDA-II (factory equipped)"
−```
−
−# Certifying Body {toc}
−
−## The certifying body that lists the assembly determines which approved-assemblies list it can appear on and which markets it can be sold into. {note}
−
−## The certifying bodies required for the assemblies used in this installation shall be specified.
−
−```datasheet
−label: Certifying Bodies Required for This Installation
−type: checkbox
−options:
− - "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)"
−default:
− - "ASSE International (ASSE 1013, 1015, 1020, 1056, 1012, 1001, 1011, 1047, 1048 as applicable)"
−```
−
−## 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. {note}
−
−# Installation {toc}
−
−## Orientation {toc}
−
−```datasheet
−label: Installed Orientation
−type: select
−options:
− - "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)"
−default: "Horizontal — assembly axis level, test cocks accessible"
−```
−
−### Each assembly shall be installed in the orientation listed by the certifying body for that assembly.
−
−### 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. {note}
−
−### The Contractor shall verify the listed orientations on the specific model's USC FCCCHR approval before installing in any orientation other than horizontal.
−
−## Clearance for Testing and Service {toc}
−
−### Each assembly shall be installed with clearance on all sides sufficient to permit field testing, parts replacement, and inspection.
−
−```datasheet
−label: Installation Clearance Requirements
−type: checkbox
−options:
− - "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"
−default: "12 in. minimum above the assembly (ceiling / soffit / structure)"
−```
−### 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. {note}
−
−### 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.
−
−## Installation Height — Backflow Prevention Assemblies {toc}
−
−### 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.
−
−```datasheet
−label: Installation Height — Bottom of Assembly Above Finished Floor
−type: range
−unit: in
−options:
− min: 12
− max: 60
− setpoints: [12, 24, 30, 36, 48, 60]
−default: 36
−```
−
−### 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. {note}
−
−## Indirect Waste — RPZ and RPDA-II Relief Discharge {toc}
−
−### The indirect waste receptor for the relief discharge of every RPZ and RPDA-II assembly is governed by the following requirements. {note}
−
−### 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.
−
−```datasheet
−label: Indirect Waste Air Gap Above Receptor
−type: range
−unit: in
−options:
− min: 1
− max: 12
− step: 0.5
−default: 2
−```
−
−### 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 [[sync/sanitary-waste-and-vent-piping]].
−
−```datasheet
−label: Indirect Waste Receptor for RPZ / RPDA-II Relief Discharge
−type: select
−options:
− - "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)"
−default: "Floor drain with trap and vent, sized for worst-case relief discharge"
−```
−
−### 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.
−
−### The indirect waste receptor shall be sized for the worst-case relief-valve discharge rate.
−
−```datasheet
−label: Indirect Waste Receptor Sized For
−type: radio
−options:
− - "Worst-case relief-valve discharge rate per manufacturer's published curve"
− - "Sized per [[sync/sanitary-waste-and-vent-piping]] indirect waste sizing"
−default: "Worst-case relief-valve discharge rate per manufacturer's published curve"
−```
−
−### 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. {note}
−
−### The Contractor shall confirm the receptor's drain capacity (the connected drainage piping and trap size) against the worst-case relief-discharge rate.
−
−## Drain Pan or Drain Lines Are Not Substitutes {toc}
−
−### 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.
−
−### 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. {note}
−
−### The relief discharge shall be vertical and unrestricted to the indirect-waste air gap.
−
−## Supports {toc}
−
−```datasheet
−label: Assembly Support Method
−type: select
−options:
− - "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"
−default: "Dedicated floor stand"
−```
−
−### Each assembly shall be supported independently of the connected piping.
−
−### 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.
−
−### 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.
−
−### The significant weight of assemblies 6 inches and larger shall not be transferred to the connected piping.
−
−### Seismic restraint shall be provided per [[sync/domestic-water-piping]] where the project Seismic Design Category requires it.
−
−## Shut-Off Valves and Strainer {toc}
−
−### 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. {note}
−
−### The Contractor shall not substitute, modify, or remove the factory-equipped shut-off valves.
−
−### 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.
−
−```datasheet
−label: Upstream Strainer Provided
−type: radio
−options:
− - "Yes — wye-strainer with blowdown valve upstream of assembly"
− - "No — assembly inlet not protected by separate strainer"
−default: "Yes — wye-strainer with blowdown valve upstream of assembly"
−```
−
−### Strainers are recommended on new-construction installations and on installations downstream of water main work where construction debris is likely. {note}
−
−### 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.
−
−## Bypass Provisions {toc}
−
−```datasheet
−label: Parallel Backflow Assembly Bypass Provided
−type: radio
−options:
− - "Yes — parallel bypass with second assembly of equal rating (critical loads)"
− - "No — service interruption acceptable during annual testing"
−default: "No — service interruption acceptable during annual testing"
−```
−
−### 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.
−
−### The bypass shall be valved and shall be controlled by the Owner's procedures during testing.
−
−### 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.
−
−# Freeze Protection and Outdoor Installation {toc}
−
−## Indoor Installation Preferred {toc}
−
−### 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.
−
−### 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.
−
−## Outdoor or Unconditioned Space — Heated Enclosure Required {toc}
−
−### 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.
−
−```datasheet
−label: Outdoor / Unconditioned Installation Freeze Protection
−type: select
−options:
− - "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"
−default: "Not applicable — installed indoors in heated space"
−```
−
−```datasheet
−label: Heated Enclosure Setpoint
−type: range
−unit: °F
−options:
− min: 35
− max: 60
− setpoints: [35, 40, 45, 50, 60]
−default: 40
−```
−
−```datasheet
−label: Heated Enclosure Heater Wattage
−type: range
−unit: W
−drawing_ref: true
−options:
− min: 100
− max: 2400
− setpoints: [100, 200, 400, 800, 1500, 2400]
−default: 400
−```
−
−### Where assemblies must be installed outdoors or in unconditioned spaces in regions subject to freezing, a heated enclosure ("hot box") shall be provided.
−
−### 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.
−
−### 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.
−
−## Below-Grade Vaults {toc}
−
−### 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.
−
−### 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.
−
−# Testing and Commissioning {toc}
−
−## Initial Commissioning Test {toc}
−
−### 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. {note}
−
−### Every backflow prevention assembly installed under this scope shall be commissioned by a certified tester before the assembly is placed in service.
−
−```datasheet
−label: Initial Commissioning Test Performed By
−type: radio
−options:
− - "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"
−default: "ASSE 5110 (or state equivalent) certified tester engaged by the Contractor"
−```
−
−### 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.
−
−## Test Report {toc}
−
−### The test report shall be on the form required by the water purveyor or the AHJ.
−
−### 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.
−
−## Submission and Tagging {toc}
−
−### 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).
−
−### 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.
−
−### The tag shall remain affixed to the assembly throughout its service life; subsequent annual test reports are tracked by the assembly's unique identifier.
−
−## Annual Recertification {toc}
−
−```datasheet
−label: Annual Retest Tagging at Installation
−type: checkbox
−options:
− - "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)"
−default: "Permanent weather-resistant tag affixed to assembly"
−```
−
−### After initial commissioning, every testable backflow prevention assembly shall be retested at least annually by a certified tester.
−
−### 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. {note}
−
−### The Contractor shall provide tagging and documentation that enables the Owner's facility management to schedule the annual retest.
−
−## Pressure Drop Verification {toc}
−
−### 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.
−
−### The verified pressure drop shall be recorded in the commissioning report and compared against the design assumptions.
−
−### 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.
−
−# Installation Coordination {toc}
−
−## Service Entrance Configuration {toc}
−
−### 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. {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. {note}
−### Detailed configuration is [[drawing: as indicated on the plumbing service entrance detail]]. {note}
−
−## Fire Service Configuration {toc}
−
−### 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. {note}
−### The fire-service backflow assembly is typically installed immediately downstream of the property-line vault or the fire-service entrance. {note}
−
−### The fire-service backflow assembly location shall be specified, coordinated with the fire protection engineer of record and the property-line vault location.
−
−```datasheet
−label: Fire Service Backflow Location
−type: radio
−options:
− - "Inside building at fire service entrance"
− - "Below-grade vault at property line"
− - "Heated enclosure on exterior pad at building"
−default: "Inside building at fire service entrance"
−```
−
−### Coordinate the fire-service configuration with [[sync/wet-pipe-fire-sprinkler-systems]] and with the fire protection engineer of record.
−
−## Internal Cross-Connection Inventory {toc}
−
−### The Engineer shall inventory every internal cross-connection on the project and specify in-plant backflow protection at each.
−
−```datasheet
−label: Internal Cross-Connections Protected on This Project (typical)
−type: checkbox
−options:
− - "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]])"
−default: "Boiler makeup water — RPZ (chemical treatment hazard)"
−```
−### 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). {note}
−
−# Pressure and Hydraulic Considerations {toc}
−
−## Pressure Drop {toc}
−
−### 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. {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. {note}
−
−### The Engineer shall account for the assembly pressure drop in the building's hydraulic calculation.
−
−```datasheet
−label: Assembly Pressure Drop at Design Flow
−type: range
−unit: psi
−drawing_ref: true
−options:
− min: 1
− max: 15
− step: 0.5
−default: 8
−```
−
−### 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. {note}
−
−## Closed-System Behavior {toc}
−
−### 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. {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. {note}
−
−### 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 [[sync/water-heaters]] and per the applicable plumbing code.
−
−```datasheet
−label: Thermal Expansion Tank Required (Closed System)
−type: radio
−options:
− - "Yes — required because building service entrance includes a backflow assembly"
− - "No — only where the system is verified to remain open (rare in commercial)"
−default: "Yes — required because building service entrance includes a backflow assembly"
−```
−
−## Pressure Reducing Valve Coordination {toc}
−
−### Where building service pressure exceeds 80 psi at the service entrance and a pressure reducing valve (PRV) is required per [[sync/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).
−
−### 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. {note}
−
−# Delivery, Storage, and Handling {toc}
−
−## Backflow prevention assemblies shall be delivered in their original protective packaging with end-connection covers in place.
−
−## 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.
−
−## End-connection covers shall remain in place until immediately before installation.
−
−## 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.
−
−## Assemblies that have been on site for more than 90 days before installation shall be inspected before installation.
−
−## Check disc elastomers can develop a "set" from sustained spring load during long storage with the assembly oriented horizontally. {note}
−
−## The manufacturer's published recommendations for stored-assembly inspection or refurbishment before installation shall be followed.
−
−# Warranty {toc}
−
−## The Contractor shall warrant each installed backflow prevention assembly against defects in installation and workmanship for a period of one year from substantial completion.
−
−## 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. {note}
−
−## 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.
−
−## 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.
−
−## 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.
−
−# Spare Parts {toc}
−
−## The Contractor shall deliver to the Owner at substantial completion a spare parts inventory sized for the assemblies installed on the project.
−## 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)
−
−```datasheet
−label: Spare Parts Inventory (per assembly model and size)
−type: checkbox
−options:
− - "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"
−default:
− - "First check rebuild kit (springs, seats, discs, O-rings)"
−```
−
−## 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.
−
−## 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.
+---
+title: Backflow Prevention
+category: Plumbing
+description: >
+ When to use: The assemblies and devices that keep water from flowing backward into a potable supply, in commercial, institutional, industrial, and multifamily buildings served by a utility or by a private source. Covers the building water service assembly at the point of entry, the premises isolation assembly on it, the isolation assemblies at internal cross-connections such as equipment makeup water, chemical feed, laboratory, and irrigation connections, and the detector and non-detector assemblies on a fire service supplied from a potable main. Establishes how the degree of hazard at each connection is classified, which assembly type that classification admits, the construction, listing, and lead-free certification of each assembly, its orientation, height, clearances, support, relief discharge, outdoor enclosure or vault, and the initial field test and certification by a certified tester that puts it in service.
+
+ Not intended for: Vacuum breakers integral to a listed fixture, flushometer, or faucet ([[sync/plumbing-fixtures]]); hose connection vacuum breakers and hose connection backflow preventers on hose bibbs and wall hydrants ([[sync/plumbing-specialties]]); the distribution piping beyond the premises isolation point ([[sync/domestic-water-piping]]); the site water main up to the building ([[sync/water-distribution-piping]]); the irrigation tap and the piping, zone valves, heads, and controller it serves ([[sync/landscape-irrigation]]); the sprinkler riser, the sprinkler piping, and the arrangement for the forward-flow test downstream of the detector check ([[sync/wet-pipe-fire-sprinkler-systems]]); the buried private fire main upstream of the point of entry ([[sync/underground-fire-service-mains]]); thermal expansion control at the heater ([[sync/water-heaters]]); the pressure reducing fill valve and glycol feed package downstream of the hydronic assembly ([[sync/hydronic-specialties]]); the chemistry and dosing program for a treated system ([[sync/hvac-water-treatment]]); the floor drain, floor sink, or hub drain receiving the relief discharge and the drainage piping downstream of it ([[sync/sanitary-waste-and-vent-piping]]); backflow preventers integral to listed foodservice equipment ([[sync/foodservice-equipment]]); the water purveyor's own assemblies and meters on the public side of the point of service; reclaimed, rainwater, and graywater systems; and medical gas and vacuum systems.
+---
+
+# Scope {toc}
+
+## This standard governs the assemblies and devices that protect a potable water supply from backflow: how each cross-connection is classified, which assembly that classification admits, how the assembly is built, listed, and certified, where and how it is installed, how its relief discharge is carried away, how it is protected from freezing outdoors, and how it is field tested and certified before water passes through it. {note}
+
+## The scope begins where the water service pipe enters the building, or where a branch leaves the potable piping to serve a connection that can backflow, and ends at the discharge of the assembly; it includes the main shutoff, the strainer, the meter setting where the Contractor furnishes it, the test cocks, the relief discharge air gap fitting, the outdoor enclosure or vault, and the supports that belong to the assembly. {note}
+
+## The following are governed elsewhere and are outside this standard: {note}
+
+- vacuum breakers integral to a listed fixture, flushometer, or faucet
+- hose connection vacuum breakers and hose connection backflow preventers on hose bibbs and wall hydrants
+- the distribution piping beyond the premises isolation point, including its materials, sizing, pressure test, and disinfection procedure
+- the site water main up to the building and the purveyor's own equipment on the public side of the point of service
+- the sprinkler riser, the sprinkler piping, and the arrangement for the forward-flow test downstream of the detector check
+- the buried private fire main upstream of the point of entry
+- thermal expansion control at the water heater that a closed system makes necessary
+- the pressure reducing fill valve and glycol feed package of a hydronic system
+- the receptor that takes the relief discharge and the drainage piping downstream of it
+- reclaimed, rainwater, and graywater systems, and medical gas and vacuum systems
+
+## The irrigation point of connection is one location this standard shares with another. The assembly there, its selection by hazard, its enclosure, and its testing are governed by this standard; the point of connection, and the piping, zone valves, heads, and controller downstream of the assembly, are governed by [[sync/landscape-irrigation]]. {note}
+
+## The fire service is another shared location. The detector or non-detector assembly on the fire service, its selection by hazard, its listing, and its testing are governed by this standard; the buried main that feeds it is governed by [[sync/underground-fire-service-mains]], and the riser and sprinkler piping it supplies are governed by [[sync/wet-pipe-fire-sprinkler-systems]]. {note}
+
+## Backflow reaches a potable supply by two routes: back-siphonage, in which a drop in supply pressure draws liquid from a downstream source into the supply, and back-pressure, in which a downstream system operating above supply pressure pushes its contents into the supply. An assembly is rated for one route or for both, and that rating is as much a part of its selection as the degree of hazard. {note}
+
+## The locations of the assemblies, the size of the piping at each, and the assembly type at each location shall be as indicated on [[drawing: the backflow prevention assembly schedule]].
+
+## Every assembly and device furnished under this standard shall be of a type that [[parameter: adopted-plumbing-code]] permits for the degree of hazard and the backflow route at its connection.
+
+# Referenced Standards {toc}
+
+## Assemblies, devices, enclosures, 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 Authority Having Jurisdiction, the water purveyor's cross-connection control program, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## The adopted plumbing code and the published requirements of the water purveyor's cross-connection control program shall take precedence over every other reference on any matter either addresses directly.
+
+| Standard | Title |
+|----------|-------|
+| IPC | International Plumbing Code |
+| UPC | Uniform Plumbing Code |
+| NFPA 13 | Standard for the Installation of Sprinkler Systems |
+| NFPA 24 | Standard for the Installation of Private Fire Service Mains and Their Appurtenances |
+| NFPA 70 | National Electrical Code |
+| ASSE 1001 | Performance Requirements for Atmospheric Type Vacuum Breakers |
+| ASSE 1012 | Performance Requirements for Backflow Preventers with Intermediate Atmospheric Vent |
+| 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 1024 | Performance Requirements for Dual Check Backflow Preventers |
+| ASSE 1047 | Performance Requirements for Reduced Pressure Detector Fire Protection Backflow Prevention Assemblies |
+| ASSE 1048 | Performance Requirements for Double Check Detector Fire Protection Backflow Prevention Assemblies |
+| ASSE 1056 | Performance Requirements for Spill Resistant Vacuum Breakers |
+| ASSE 1060 | Performance Requirements for Outdoor Enclosures for Fluid Conveying Components |
+| ASSE 5110 | Professional Qualifications Standard for Backflow Prevention Assembly Testers |
+| ASME A112.1.2 | Air Gaps in Plumbing Systems |
+| AWWA C510 | Double Check Valve Backflow Prevention Assembly |
+| AWWA C511 | Reduced-Pressure Principle Backflow Prevention Assembly |
+| AWWA M14 | Backflow Prevention and Cross-Connection Control: Recommended Practices |
+| USC FCCCHR Manual | Manual of Cross-Connection Control, Foundation for Cross-Connection Control and Hydraulic Research, University of Southern California |
+| NSF/ANSI/CAN 61 | Drinking Water System Components — Health Effects |
+| NSF/ANSI/CAN 372 | Drinking Water System Components — Lead Content |
+| UL 1469 | Reduced Pressure Principle Backflow Preventers |
+| UL 312 | Check Valves for Fire-Protection Service |
+| FM 1210 | Approval Standard for Backflow Preventers |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
+
+## The ASSE performance standards define each assembly type and the test it must pass to be listed; the USC Foundation list and the state program lists record which listed models a purveyor accepts; the AWWA standards cover the large waterworks-grade assemblies a purveyor may require at a service connection; and the UL and FM standards cover the same assemblies when they serve a fire protection system. One assembly commonly carries several of these marks. {note}
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following for review before any assembly, device, or enclosure is procured:
+
+- product data for each assembly and device, giving the ASSE standard it is listed to, the assembly type, the size, the body and trim materials, the end connections, the shutoff valve type, the rated working pressure and temperature, the orientations for which it is approved, and its published pressure loss curve
+- the entry for each assembly on the approved assemblies list this standard requires, at the size and in the orientation proposed
+- the NSF/ANSI/CAN 61 and NSF/ANSI/CAN 372 certification of each assembly and device installed on potable water
+- for each fire service assembly, its UL listing or FM approval for fire protection service and its detector meter data
+- the published maximum relief valve discharge rate of each reduced pressure principle assembly, with the receptor or enclosure drain that will receive it identified
+- product data for each outdoor enclosure, giving its ASSE 1060 class, material, dimensions, heater rating and electrical characteristics, thermostat, drain capacity, and lock
+- an installation drawing of each assembly showing the shutoff valves, test cocks, strainer, relief discharge air gap fitting, receptor, supports, clearances, and the height above the floor or grade
+
+```datasheet
+label: Action Submittal Package
+type: checkbox
+options:
+ - "Assembly and device product data"
+ - "Approved assemblies list entries"
+ - "NSF/ANSI/CAN 61 and 372 certifications"
+ - "Fire service assembly listing and detector meter data"
+ - "Relief valve discharge rate and receiving drain"
+ - "Outdoor enclosure product data"
+ - "Assembly installation drawings"
+```
+
+### No assembly, device, or enclosure shall be ordered until the corresponding action submittals have been reviewed and returned.
+
+## Informational Submittals {toc}
+
+### The Contractor shall submit the following supporting records before the initial certification test of any assembly:
+
+- the current certification of each tester who will perform the initial certification test, under the program this standard requires
+- the calibration certificate of each differential pressure test kit that will be used, dated within the interval this standard sets
+- the water purveyor's written confirmation of the assembly type it accepts at the service connection and at each fire service, where the purveyor's program requires that confirmation
+- the test report form the purveyor or the Authority Having Jurisdiction requires
+- seismic restraint calculations or the pre-approved restraint detail for each assembly this standard requires to be restrained
+
+```datasheet
+label: Informational Submittal Package
+type: checkbox
+options:
+ - "Tester certifications"
+ - "Test kit calibration certificates"
+ - "Purveyor confirmation of assembly type"
+ - "Required test report form"
+ - "Seismic restraint calculations or detail"
+```
+
+## Closeout Submittals {toc}
+
+### The Contractor shall submit the following before the assemblies are accepted:
+
+- the initial certification test report of every assembly, signed by the tester, on the required form
+- evidence that each test report was filed with the water purveyor and the Authority Having Jurisdiction within the time their programs allow
+- a schedule of the installed assemblies giving, for each, its tag identifier, type, manufacturer, model, size, serial number, location, installation date, test date, and next test date
+- an as-built drawing of each assembly installation recording its final location, orientation, height, and the receptor or drain that takes its relief discharge
+- operation and maintenance data for each assembly model, including the exploded parts diagram with part numbers and the field test procedure
+- warranty documentation for each assembly and enclosure, identifying the coverage period and the date coverage begins
+- a signed receipt from the Owner for the spare parts delivered
+
+```datasheet
+label: Closeout Submittal Package
+type: checkbox
+options:
+ - "Initial certification test reports"
+ - "Evidence of filing with purveyor and Authority Having Jurisdiction"
+ - "Installed assembly schedule"
+ - "As-built installation drawings"
+ - "Operation and maintenance data"
+ - "Warranty documentation"
+ - "Spare parts receipt"
+```
+
+# Quality Assurance {toc}
+
+## Installer and Tester Qualifications {toc}
+
+### Each assembly shall be installed by personnel holding the plumbing license the Authority Having Jurisdiction requires, and by personnel registered with the water purveyor's cross-connection control program where that program registers installers.
+
+### Each field test of an assembly shall be performed by a tester holding a current certification that the water purveyor's cross-connection control program accepts.
+
+### Where the purveyor's program names no certification, the tester shall hold a current certification to ASSE 5110 or a current certification issued by the state cross-connection control program having jurisdiction.
+
+### A test performed by a tester whose certification has lapsed at the time of the test is not a certification test under this standard, and shall be repeated by a certified tester at the Contractor's cost.
+
+### Where [[parameter: site-water-supply-source]] is a private well or another supply not furnished by a water purveyor, the cross-connection requirements of the Authority Having Jurisdiction apply wherever this standard names the purveyor's program.
+
+## Approved Assemblies {toc}
+
+### Each assembly shall appear, at its size and for the orientation in which it is installed, on the approved assemblies list indicated in the datasheet.
+
+```datasheet
+label: Approved Assemblies List Required
+type: select
+options:
+ - "USC Foundation for Cross-Connection Control and Hydraulic Research list"
+ - "State cross-connection control program list"
+ - "Water purveyor's own approved list"
+ - "ASSE listing with no separate approved list"
+```
+
+### An ASSE listing records that a model passed the laboratory test its performance standard sets. The USC Foundation list records that a model also completed a year of field evaluation in a specific size and orientation, and many purveyors and several states accept only models on that list or on a state list built from it; where a purveyor keeps its own list, that list governs the purveyor's service connection whatever else the model carries. A jurisdiction that accepts the ASSE listing alone admits the widest range of models and the smallest range of orientations proven by field evaluation. {note}
+
+### The Contractor shall confirm the approval status of each proposed model with the purveyor's program before it is ordered, and shall not install a model that the program has removed from its list after the submittal was reviewed.
+
+### An approval that covers an assembly in one orientation does not cover it in another, and the same model is often approved horizontally at every size and vertically at only some. {note}
+
+## Lead-Free and Health Effects Certification {toc}
+
+### Every assembly and device that conveys potable water shall be certified to NSF/ANSI/CAN 61 for health effects and to NSF/ANSI/CAN 372 for lead content.
+
+### The lead-free limit that NSF/ANSI/CAN 372 verifies is set by Section 1417 of the Safe Drinking Water Act and shall not be waived at the project level.
+
+### A fire service assembly on a service that supplies no potable water, and that is not interconnected with the potable piping downstream of its own assembly, is exempt from the lead content limit by the terms of the Act; the exemption is lost the moment a potable branch is taken from the fire service. {note}
+
+### Where a fire service shares its piping with any potable use, the fire service assembly shall be certified to NSF/ANSI/CAN 372.
+
+# Hazard Classification and Assembly Selection {toc}
+
+## Degree of Hazard and Backflow Route {toc}
+
+### The degree of hazard at each cross-connection shall be classified as a health hazard or a non-health hazard under [[parameter: adopted-plumbing-code]] and the water purveyor's cross-connection control program, and the classification shall be recorded on [[drawing: the backflow prevention assembly schedule]].
+
+### A health hazard is a connection to any substance that could cause illness or death if it entered the supply: treated boiler and hydronic water, cooling tower water, chemical feed, laboratory and medical equipment, irrigation, sewage and process water, and any supply of unknown quality. A non-health hazard is a connection to a substance that would degrade the taste, color, odor, or temperature of the supply without endangering health. The classification is the purveyor's to make under its program, and a purveyor may classify a whole premises by its occupancy regardless of what is inside. {note}
+
+### The backflow route at each cross-connection shall be identified as back-siphonage only or as back-pressure, and a connection downstream of any pump, boiler, elevated tank, pressurized vessel, or chemical injector shall be identified as back-pressure.
+
+### An assembly rated for both routes is acceptable at a connection subject to either; an assembly rated for back-siphonage only is acceptable only where no back-pressure can occur. {note}
+
+### The Engineer of Record shall survey every connection between the potable piping and any other system, vessel, or equipment on the project and shall record each one, with its classification and its protection, on the assembly schedule.
+
+### A cross-connection that is not on the schedule is one that nobody protected, and the purveyor's inspector finds it at the premises survey after occupancy, when the fix is a change order rather than a line on a drawing. {note}
+
+## Assembly Type by Hazard and Route {toc}
+
+### A health hazard connection shall be protected by an air gap or by a reduced pressure principle assembly, and a health hazard fire service shall be protected by a reduced pressure detector assembly or a reduced pressure principle assembly as the fire service article of this standard directs.
+
+### A non-health hazard connection subject to back-pressure shall be protected by a double check valve assembly or by an assembly acceptable for a health hazard.
+
+### A non-health hazard connection subject to back-siphonage only shall be protected by a pressure vacuum breaker assembly, a spill resistant vacuum breaker assembly, an atmospheric vacuum breaker, or an assembly acceptable for back-pressure.
+
+### A health hazard connection subject to back-siphonage only may be protected by a pressure vacuum breaker assembly or a spill resistant vacuum breaker assembly where [[parameter: adopted-plumbing-code]] and the purveyor's program permit a vacuum breaker for that application.
+
+### A reduced pressure principle assembly protects against both routes and both hazards and is the one assembly that also protects when both its checks have fouled, because its relief valve opens the zone to atmosphere; it costs the most, loses the most pressure, and discharges water on every relief event, so it needs a drain. A double check valve assembly protects against both routes at lower cost and lower pressure loss but gives no warning when a check fails. A pressure vacuum breaker and a spill resistant vacuum breaker cost the least but protect against back-siphonage only, and the pressure vacuum breaker spills from its air inlet each time it is pressurized, which the spill resistant type does not. {note}
+
+### A dual check backflow preventer listed to ASSE 1024, or a backflow preventer with intermediate atmospheric vent listed to ASSE 1012, shall be used only at a connection where [[parameter: adopted-plumbing-code]] permits a device without test cocks for that application and the purveyor's program accepts it.
+
+### A dual check and an intermediate vent device have no shutoff valves and no test cocks, so they cannot be field tested; the codes admit them at small residential and appliance connections where the hazard is low and a testable assembly is out of proportion to the connection, and a purveyor's program may refuse them at any connection it classifies. {note}
+
+### Where an air gap is selected, the vertical distance from the outlet to the flood level rim of the receiving vessel shall be not less than twice the effective opening of the outlet and not less than 1 in., in accordance with ASME A112.1.2, and the air gap shall not be reduced by any fitting, hose, or extension.
+
+### An air gap is the only protection that has no moving parts and nothing to test; it also breaks the pressure, so whatever is downstream of it must be refilled by gravity or repumped, which is why it serves tanks and receptors rather than pressurized piping. {note}
+
+### A check valve, a pressure reducing valve, or a water meter shall not be substituted for an assembly required by this standard.
+
+# Building Water Service Assembly {toc}
+
+## The building water service assembly is the equipment on the service pipe between its entry into the building and the start of the distribution piping: the main shutoff, the meter setting where the purveyor has the Contractor furnish it, the strainer where one is selected, the premises isolation assembly, and the relief discharge of that assembly. {note}
+
+## A premises isolation assembly shall be installed on the building water service wherever [[parameter: adopted-plumbing-code]] or the water purveyor's program requires containment of the premises, and its type shall be as the purveyor's program requires for the occupancy.
+
+## A purveyor requires premises isolation to protect the public main from whatever may happen inside a building it cannot inspect, and it requires isolation at individual connections to protect the building's own occupants; the two are not alternatives, and a premises assembly does not relieve any internal connection of its own protection. {note}
+
+## The premises isolation assembly shall be installed downstream of the meter and the main shutoff, and upstream of every branch, treatment unit, pressure reducing valve, booster pump, and water heater, so that no outlet of the building is on the supply side of it.
+
+## A pressure booster package ([[sync/domestic-water-booster-pumps]]), treatment equipment, and a pressure reducing valve shall each be located on the premises side of the isolation assembly.
+
+## A pressure reducing valve downstream of a reduced pressure principle assembly also leaves the assembly's relief valve referenced to full supply pressure, which is the condition in which the assembly was listed; a reducing valve upstream of the assembly lowers that reference and lets the relief valve open on ordinary pressure swings. {note}
+
+## The pressure reducing arrangement itself, where the supply pressure requires one, is furnished under [[sync/domestic-water-piping]]. {note}
+
+## Where the meter is furnished by the purveyor, the Contractor shall provide the meter setting, the shutoff on each side of it, and the spool or setter the purveyor's standard requires, and shall coordinate the meter installation date with the purveyor.
+
+## A premises isolation assembly, or a check valve in a meter, makes the building a closed system in which heated water has no path back to the main; the thermal expansion control that follows is selected under [[sync/water-heaters]] from that fact, and the determination recorded here is what that selection reads. {note}
+
+# Equipment and Process Connections {toc}
+
+## Each connection from the potable piping to a boiler, hydronic loop, cooling tower, humidifier, chemical feed, laboratory, medical, foodservice, process, or irrigation system shall be protected by its own assembly, of the type the hazard classification article admits for that connection, at the location indicated on [[drawing: the backflow prevention assembly schedule]].
+
+## The makeup water connection to a boiler, a hydronic loop, or a cooling tower shall be protected by a reduced pressure principle assembly or an air gap, unless the water purveyor's program classifies the system as a non-health hazard in writing.
+
+## A hydronic loop that is dosed with corrosion inhibitor, biocide, or glycol is a health hazard by every model code and every purveyor program; an undosed loop filled only with potable water is the case on which jurisdictions differ, and the purveyor's written classification, not the designer's expectation, decides whether a double check may serve it. {note}
+
+## The pressure reducing fill valve and glycol feed package downstream of the hydronic assembly are furnished under [[sync/hydronic-specialties]], and the basin level control and fill valve at the tower are furnished under [[sync/cooling-towers]]. {note}
+
+## The chemistry and dosing program for a treated system is the subject of [[sync/hvac-water-treatment]]; this standard furnishes the assembly on the water that feeds it. {note}
+
+## A connection through which a chemical is injected into the potable supply shall be protected by a reduced pressure principle assembly on the supply to the injection point or by an air gap at the injection point, and the injection point shall be on the premises side of the isolation assembly.
+
+## The treatment equipment itself, its metering pumps, and its interlocks are furnished under [[sync/domestic-water-softeners-and-filtration]]. {note}
+
+## The assembly at the irrigation point of connection shall be a reduced pressure principle assembly unless [[parameter: adopted-plumbing-code]] and the purveyor's program permit a double check valve assembly or a pressure vacuum breaker assembly for an irrigation system with no chemical injection and no elevation or pump that can produce back-pressure.
+
+## Irrigation is classified as a health hazard wherever fertilizer or pesticide can be drawn into the piping, which is nearly everywhere a lawn is fed; a pressure vacuum breaker survives in the codes for the simple sprinkler system with no injection, no booster, and no zone above the assembly, and the purveyor's program is where that permission is confirmed or withdrawn. {note}
+
+## The potable supply to a steam or evaporative humidifier shall be protected by a reduced pressure principle assembly or an air gap, at the humidifier or at the branch serving a group of humidifiers.
+
+## A connection to laboratory, medical, dialysis, dental, mortuary, or photographic equipment shall be protected by a reduced pressure principle assembly or an air gap, at the equipment or at the branch serving a group of such equipment as indicated on [[drawing: the backflow prevention assembly schedule]].
+
+## A connection to a carbonated beverage dispenser or to another item of foodservice equipment shall be protected by the device listed with that equipment, and where none is, by a reduced pressure principle assembly on the branch serving it.
+
+## Backflow preventers integral to listed foodservice equipment are furnished with that equipment under [[sync/foodservice-equipment]]. {note}
+
+# Fire Service Assemblies {toc}
+
+## Requirements in this section apply to each assembly on a fire service supplied from a potable main, as indicated on [[drawing: the backflow prevention assembly schedule]].
+
+## The fire service assembly type shall be as indicated in the datasheet.
+
+```datasheet
+label: Fire Service Assembly Type
+type: select
+derived: "the degree of hazard [[parameter: adopted-plumbing-code]] and the water purveyor assign to the fire protection system, and whether the purveyor requires detection of unmetered flow on the fire service"
+options:
+ - "Double check detector assembly"
+ - "Reduced pressure detector assembly"
+ - "Double check valve assembly without detector"
+ - "Reduced pressure principle assembly without detector"
+default: derived
+```
+
+## A detector assembly adds a metered bypass around the main checks so that the purveyor can see the small flows a leak, a theft, or an unauthorized connection would otherwise pass unseen through a fire service that has no meter of its own; where the fire service is metered by the purveyor, or where the purveyor does not require detection, the assembly without the bypass is the same protection at lower cost. A double check is the usual choice for a wet sprinkler system filled only with potable water; a reduced pressure type is required where the system contains antifreeze, foam concentrate, or a chemical additive, where it is fed from an auxiliary tank, pond, or well, or wherever the purveyor classifies the system as a health hazard. {note}
+
+## Each fire service assembly shall be listed to ASSE 1047 or ASSE 1048, as its type requires, and shall carry the fire protection listing indicated in the datasheet.
+
+```datasheet
+label: Fire Service Assembly Approval
+type: radio
+options:
+ - "UL listed for fire protection service"
+ - "UL listed and FM approved for fire protection service"
+default: "UL listed for fire protection service"
+```
+
+## NFPA 13 requires every component in the water supply to a sprinkler system to be listed for fire protection service, and the UL listing satisfies that; FM approval is the additional mark an insurer may require of a property it covers, and it changes the assembly's documentation and sometimes its shutoff valves without changing the protection it gives. {note}
+
+## The shutoff valves of each fire service assembly shall be of an indicating type that NFPA 13 accepts for a control valve in the water supply, and shall be arranged for electrical supervision as [[sync/fire-protection-piping]] requires.
+
+## The detector meter of each detector assembly shall register in the unit the water purveyor requires and shall be installed so that it can be read without removing any part of the assembly or enclosure.
+
+## The Contractor shall record the detector meter reading at the initial certification test and shall report it to the purveyor with the test report, so that any flow registered afterward is known to have occurred in service.
+
+## The Contractor shall report the pressure loss of the fire service assembly at the sprinkler system demand, taken from the published curve of the model furnished, to the Engineer of Record and to the fire protection designer before the assembly is ordered.
+
+## A fire service assembly consumes pressure the sprinkler system needs, and a reduced pressure type consumes two to three times what a double check does; the hydraulic calculation under [[sync/wet-pipe-fire-sprinkler-systems]] carries that loss, and an assembly changed after the calculation was run is the usual reason a system fails its acceptance flow test. {note}
+
+## Each fire service assembly shall be installed so that it can be flowed at the sprinkler system demand for the forward-flow test NFPA 13 requires, through the arrangement furnished under [[sync/wet-pipe-fire-sprinkler-systems]].
+
+## A strainer shall not be installed in a fire service upstream of the assembly unless the fire protection Authority Having Jurisdiction accepts it in writing.
+
+## Fire codes resist strainers in a fire service because a strainer screen that clogs during a fire closes the supply to the sprinklers; the assembly's own checks tolerate the debris a strainer would catch. {note}
+
+# Assembly Construction {toc}
+
+## Sizing and Pressure Loss {toc}
+
+### Each assembly shall be the same nominal size as the piping in which it is installed unless the assembly schedule indicates a different size for it.
+
+### An assembly larger than its design flow needs runs with its checks barely open, and the checks chatter and wear at low flow; an assembly smaller than the line loses more pressure than the hydraulic calculation allowed. The size on the schedule is the Engineer's balance of the two against the published loss curve of the assembly type. {note}
+
+### The pressure loss of each premises isolation assembly and each fire service assembly at its design flow, taken from the published curve of the model furnished, shall not exceed the loss indicated in the datasheet.
+
+```datasheet
+label: Maximum Pressure Loss at Design Flow
+type: range
+unit: psi
+options:
+ min: 2
+ max: 20
+ step: 0.5
+```
+
+### Where the datasheet indicates no maximum loss, the Contractor shall report the published loss of each premises isolation assembly at its design flow to the Engineer of Record before the assembly is ordered.
+
+### A double check loses a few psi at its design flow and a reduced pressure principle assembly loses roughly ten, and the loss is in series with every fixture and sprinkler the assembly supplies; where the supply pressure is marginal the assembly type and the booster pump are one decision. {note}
+
+## Pressure and Temperature Rating {toc}
+
+### Each assembly and device shall be rated for a working pressure of not less than 175 psi and not less than [[parameter: site-water-supply-pressure-maximum]] at its inlet.
+
+### Each assembly installed on water above 110°F shall be a model listed for the water temperature it will see, and shall carry that temperature on its product data.
+
+### The standard assembly is listed for cold water at 110°F or less, and its elastomer checks and relief diaphragm harden and leak in hot water; a makeup connection taken from the hot water piping, a hot water chemical feed, or a tempered irrigation line needs a hot water model listed to the same ASSE standard. {note}
+
+## Body Material and End Connections {toc}
+
+### The body material of each assembly 2 in. and smaller shall be as indicated in the datasheet.
+
+```datasheet
+label: Body Material, Assemblies 2 in. and Smaller
+type: radio
+options:
+ - "Lead-free copper alloy"
+ - "Stainless steel"
+default: "Lead-free copper alloy"
+```
+
+### A lead-free copper alloy body is the norm at small sizes and is what every listed small assembly is cast in; a stainless steel body is chosen where the water is aggressive to copper alloy, where the assembly is in a corrosive atmosphere, or where the Owner standardizes on it, at a higher cost and a longer lead time. {note}
+
+### The body material of each assembly 2-1/2 in. and larger shall be as indicated in the datasheet.
+
+```datasheet
+label: Body Material, Assemblies 2-1/2 in. and Larger
+type: select
+options:
+ - "Epoxy-coated ductile iron"
+ - "Stainless steel"
+ - "Lead-free copper alloy"
+default: "Epoxy-coated ductile iron"
+```
+
+### Epoxy-coated ductile iron is the norm at large sizes and is the lightest and least costly body; stainless steel is chosen for aggressive water, a corrosive location, or a vault that floods, and lead-free copper alloy is available at the smaller end of the large range where the Owner wants a non-ferrous body without the cost of stainless. {note}
+
+### A ductile iron body shall be coated inside and out with a fusion-bonded epoxy that is part of the assembly's NSF/ANSI/CAN 61 certification.
+
+### Assemblies 2 in. and smaller shall have threaded end connections to ASME B1.20.1, or union ends where the model furnishes them.
+
+### The end connections of each assembly 2-1/2 in. and larger shall be as indicated in the datasheet.
+
+```datasheet
+label: End Connections, Assemblies 2-1/2 in. and Larger
+type: radio
+options:
+ - "Flanged"
+ - "Grooved"
+```
+
+### Flanged ends match the flanged shutoff valves that most purveyors and fire codes expect, and they hold the assembly rigid between two anchored valves; grooved ends make a large assembly faster to install and to lift out for repair, at the price of the couplings' own listing and a rigid-coupling requirement where the assembly must not deflect. {note}
+
+### The end connections of each assembly shall match the piping material and joining method on each side of it, and a transition fitting listed for both materials shall be provided where they differ.
+
+## Shutoff Valves and Test Cocks {toc}
+
+### Each assembly shall be furnished with the two shutoff valves and the test cocks of the model as listed, and no shutoff valve or test cock shall be substituted, removed, plugged, or added.
+
+### An assembly is listed as a whole, from the inlet shutoff to the outlet shutoff, and a shutoff valve replaced with a different type is not the listed assembly; the test cocks are the only means a tester has of reading the checks. {note}
+
+### The shutoff valves of each assembly 2 in. and smaller shall be full-port ball valves.
+
+### The shutoff valves of each assembly 2-1/2 in. and larger shall be as indicated in the datasheet.
+
+```datasheet
+label: Shutoff Valves, Assemblies 2-1/2 in. and Larger
+type: select
+options:
+ - "Resilient-seated outside screw and yoke gate valves"
+ - "Non-rising stem resilient-seated gate valves"
+ - "Gear-operated butterfly valves with position indicator"
+```
+
+### An outside screw and yoke gate shows its position from across the room and is what a fire code requires on a fire service; a non-rising stem gate fits where there is no headroom for a rising stem, at the cost of showing nothing about its position; a gear-operated butterfly is shorter and lighter than either gate and is accepted by many purveyors and, with a listed indicator, by the fire codes, while adding its own pressure loss and its own disc in the flow path during a test. {note}
+
+### Each test cock shall be a resilient-seated ball type with a threaded outlet matching the tester's hose fittings, and shall be certified lead-free as part of the assembly.
+
+### Test cocks shall be plugged or capped when not in use, and the plugs or caps shall be delivered with the assembly.
+
+## Relief Valve and Air Gap Fitting {toc}
+
+### The relief valve of each reduced pressure principle assembly and reduced pressure detector assembly shall discharge downward through an air gap drain fitting furnished by the assembly manufacturer for the model and size.
+
+### The air gap drain fitting shall maintain an air gap of not less than twice the diameter of the relief port and not less than 1 in. between the relief port and the drain line, and the drain line from the fitting shall be not smaller than the fitting's outlet.
+
+### The air gap fitting is what keeps the relief valve from ever being submerged, backed up, or pressurized by the drain; a relief valve hard-piped to a drain can neither be seen discharging nor vent the zone, and the assembly stops protecting while looking intact. {note}
+
+### Each reduced pressure principle assembly shall be installed so that its relief valve discharge can be seen from the floor or grade without removing any cover.
+
+## Vacuum Breaker Assemblies {toc}
+
+### Each pressure vacuum breaker assembly and spill resistant vacuum breaker assembly shall be installed with its air inlet upward, not less than 12 in. above the highest downstream outlet, piping, or sprinkler head, and in a location where its air inlet can discharge to atmosphere without obstruction.
+
+### Each atmospheric vacuum breaker installed in a line shall be installed not less than 6 in. above the highest downstream outlet, and shall have no shutoff valve, solenoid, or other means of holding pressure downstream of it.
+
+### An atmospheric vacuum breaker vents only when its disc drops under no pressure, and a disc held up by continuous pressure for more than the few hours the code allows takes a set and stops dropping; the downstream shutoff rule is what keeps the device able to work, and it is also why the device cannot be tested. {note}
+
+### No vacuum breaker assembly shall be installed in a pit, vault, or enclosure in which water can rise to its air inlet.
+
+## Strainer {toc}
+
+### An inlet strainer shall be provided ahead of each assembly on a domestic water service or branch as indicated in the datasheet.
+
+```datasheet
+label: Inlet Strainer on Domestic Service Assemblies
+type: radio
+options:
+ - "Strainer provided ahead of each assembly"
+ - "No strainer"
+```
+
+### A strainer keeps the construction debris and main-break grit of a new service off the check seats, which is what fouls a new assembly on its first test; it also adds pressure loss, a blowdown that must be piped and opened, and a screen that nobody cleans, and several purveyors prohibit it ahead of a premises assembly on the ground that it hides a fouled main. {note}
+
+### Where a strainer is provided, it shall be a Y-pattern or basket strainer with a stainless steel screen, a blowdown valve piped to the relief discharge receptor, and a body certified to NSF/ANSI/CAN 61 and 372, installed between the main shutoff and the assembly inlet shutoff.
+
+# Continuity of Service {toc}
+
+## The arrangement of the premises isolation assembly for continuity of service shall be as indicated in the datasheet.
+
+```datasheet
+label: Premises Isolation Arrangement
+type: radio
+options:
+ - "Single assembly"
+ - "Parallel assemblies each sized for the full demand"
+ - "Parallel assemblies each sized for a share of the demand"
+default: "Single assembly"
+```
+
+## A single assembly is the norm and is out of service for the hour its annual test and any repair take. Two parallel assemblies each sized for the full demand keep the building at full supply through the test of either, at twice the first cost and the floor space. Two assemblies each sized for a share of the demand cost little more than one large assembly, keep a reduced supply through a test, and let the building run on one assembly at low flow where a single large assembly would chatter. {note}
+
+## Where parallel assemblies are selected, each shall be a complete listed assembly with its own shutoff valves and test cocks, and each shall be tested and tagged separately.
+
+## Where parallel assemblies are selected, a pipe connecting the two assemblies shall be made only on the supply side of both inlet shutoffs and on the premises side of both outlet shutoffs.
+
+# Installation {toc}
+
+## Location and Orientation {toc}
+
+### Each assembly shall be installed in the location indicated on [[drawing: the plumbing plans]], in a space where it is accessible for testing and repair without entering a confined space, removing a ceiling, or moving equipment.
+
+### Each assembly shall be installed horizontally, with its test cocks upward and its relief valve downward, unless another orientation is indicated on [[drawing: the plumbing details]].
+
+### Where an orientation other than horizontal is indicated, the model furnished shall be approved in that orientation on the approved assemblies list this standard requires, and the Contractor shall confirm that approval before the assembly is ordered.
+
+### Most assemblies are approved horizontally in every size; vertical approval, flow up or flow down, is model-specific and size-specific, and an assembly installed in an orientation its approval does not cover is an unapproved assembly however it tests. {note}
+
+### No assembly shall be installed where its relief discharge, test cock discharge, or air inlet can be submerged, or where it is exposed to a corrosive atmosphere, to steam, or to a temperature below freezing without the enclosure this standard requires.
+
+### No assembly shall be installed in a location where a pump, elevated tank, or other source of back-pressure is on its supply side.
+
+## Height and Clearances {toc}
+
+### Each assembly shall be installed with the bottom of its body not less than 12 in. above the floor, housekeeping pad, or finished grade beneath it.
+
+### The centerline of each assembly shall be not more than the height indicated in the datasheet above the floor, housekeeping pad, or finished grade from which it is tested.
+
+```datasheet
+label: Maximum Centerline Height Above Floor or Grade
+type: range
+unit: in
+options:
+ min: 30
+ max: 72
+ setpoints: [30, 36, 42, 48, 60, 72]
+default: 60
+```
+
+### Twelve inches below the body is what lets a tester open a test cock without flooding the floor and lets the relief valve be seen discharging; a centerline above about five feet puts the test cocks over the tester's head and the gauge out of eye level, and a purveyor's program may set a lower maximum for assemblies its own inspectors reach from a ladder. {note}
+
+### Where the water purveyor's program sets a maximum height lower than the datasheet value, the program's value shall govern.
+
+### Each assembly 2 in. and smaller shall be installed with not less than 12 in. clear on each side and above it and not less than 24 in. clear in front of it.
+
+### Each assembly 2-1/2 in. and larger shall be installed with not less than 24 in. clear on each side and above it and not less than 36 in. clear in front of it.
+
+### Where the manufacturer's published clearance for removing the relief valve or a check module exceeds the clearance above, the published clearance shall govern.
+
+### Where a purveyor's program specifies clearances greater than those above, the program's clearances shall govern.
+
+## Support and Seismic Restraint {toc}
+
+### Each assembly 2-1/2 in. and larger shall be supported independently of the connected piping by a floor stand, a wall bracket, or a hanger from structure, sized for the weight of the assembly full of water.
+
+### Each assembly 2 in. and smaller may be carried by the connected piping where that piping is supported within 12 in. of each end of the assembly.
+
+### A large assembly weighs more than the pipe it sits in can carry, and an assembly supported only by its connections works its joints every time a check slams; the supports also hold the assembly square while a check module is pulled. {note}
+
+### Seismic restraint of each assembly 2-1/2 in. and larger, and of each outdoor enclosure and vault lid, shall be provided as [[sync/vibration-isolation-and-seismic-restraint]] requires for [[parameter: seismic-design-category]].
+
+### No support shall be attached to a shutoff valve body, a test cock, or the relief valve.
+
+## Relief Discharge Disposal {toc}
+
+### The relief discharge of each reduced pressure principle assembly and reduced pressure detector assembly installed indoors shall be carried by a drain line from the air gap fitting to a floor drain, floor sink, or hub drain able to receive the published maximum relief valve discharge rate of the assembly at the supply pressure.
+
+### The Contractor shall provide the published maximum relief valve discharge rate of each such assembly to the Engineer of Record before the assembly is ordered, and shall confirm that the receptor and the drainage piping furnished under [[sync/sanitary-waste-and-vent-piping]] accept it.
+
+### A relief valve on a small assembly passes a few gallons a minute when a check fails, a 2 in. assembly passes tens, and a large fire service assembly passes hundreds; a receptor sized for the drip the assembly makes in normal service floods the room on the day the assembly does its job. {note}
+
+### The relief discharge shall not be piped into a sump, a trap, or a drain line that can back up to the air gap fitting, and shall not be piped to a point above the fitting.
+
+### The relief discharge of an assembly installed outdoors shall be carried through the enclosure drain to grade, as the outdoor enclosures section of this standard requires.
+
+### Monitoring of the relief discharge shall be as indicated in the datasheet.
+
+```datasheet
+label: Relief Discharge Monitoring
+type: select
+options:
+ - "None"
+ - "Flow switch on the relief drain line alarming to the building automation system"
+ - "Water sensor at the receptor alarming to the building automation system"
+default: "None"
+```
+
+### No monitoring is the norm and is sufficient where the assembly is seen daily and its receptor can take the full discharge. A flow switch on the drain line reports the relief valve opening, which is both a failed check and a flood in progress, and suits an assembly in an unattended room above finished space. A water sensor at the receptor reports only that the receptor has overflowed, which is later and cheaper. {note}
+
+### Where monitoring is selected, the alarm contact shall be a dry contact rated for the control circuit the building automation system provides, and the switch or sensor shall be installed so that it does not restrict the drain line.
+
+## Identification {toc}
+
+### Each assembly shall carry a permanent tag giving the identifier from the installed assembly schedule, the assembly type, the size, the serial number, the installation date, and the date of its initial certification test.
+
+### The tag shall be of a weather-resistant material, attached to the assembly body or its inlet shutoff with a non-corroding fastener, and shall remain legible from the floor or grade.
+
+### Pipe identification at each assembly shall comply with [[sync/plumbing-piping-identification]].
+
+### Where parallel assemblies are installed, a permanent placard at the assemblies shall state the valve positions for normal service and for the isolation of either assembly.
+
+# Outdoor Enclosures and Vaults {toc}
+
+## Enclosure Class {toc}
+
+### Requirements in this section apply to each assembly installed outdoors or in an unheated space, as indicated on [[drawing: the plumbing plans]].
+
+### Each such assembly shall be housed in an enclosure listed to ASSE 1060 of the class indicated in the datasheet.
+
+```datasheet
+label: Outdoor Enclosure Class
+type: select
+derived: "[[parameter: site-ambient-temperature-minimum]] and whether the assembly remains in service through the freezing season"
+options:
+ - "Class I, freeze protected, heated and insulated"
+ - "Class I-V, freeze protected, for a vertical assembly"
+ - "Class II, freeze retardant, insulated without heat"
+ - "Class II-V, freeze retardant, for a vertical assembly"
+ - "Class III, weather and vandal protection without freeze protection"
+default: derived
+```
+
+### A Class I enclosure holds the assembly above freezing with a thermostatically controlled heater and insulation and is what a year-round service in a freezing climate needs; a Class II enclosure has the insulation without the heater and holds a flowing assembly through a short freeze or a drained assembly through the winter; a Class III enclosure keeps off weather and vandals and nothing else, and serves where [[parameter: site-ambient-temperature-minimum]] stays above freezing or where the assembly is drained and the supply shut for the season. The vertical classes house an assembly approved for vertical installation, such as a pressure vacuum breaker, in a taller footprint. {note}
+
+### A frozen check or relief valve cracks its body or splits its diaphragm, and the assembly is replaced rather than repaired; the enclosure is cheaper than the assembly it protects. {note}
+
+### Where the assembly is a reduced pressure type, the enclosure drain shall pass the published maximum relief valve discharge rate of the assembly without water rising to the relief valve, and the enclosure shall carry that drain rating on its listing.
+
+## Enclosure Construction {toc}
+
+### The enclosure material shall be as indicated in the datasheet.
+
+```datasheet
+label: Outdoor Enclosure Material
+type: select
+options:
+ - "Marine-grade aluminum"
+ - "Fiberglass-reinforced polymer"
+ - "Stainless steel"
+default: "Marine-grade aluminum"
+```
+
+### Aluminum is the norm, light enough to lift off for a test and resistant to weather without a coating; fiberglass is lighter still and does not dent or conduct heat, but chalks in sunlight and breaks rather than bends; stainless steel resists a corrosive or coastal atmosphere and vandalism, at the highest cost and weight. {note}
+
+### Each enclosure shall be hinged or removable so that the whole assembly, including its shutoff valves and test cocks, is accessible for testing and repair, and shall be lockable with a padlock the Owner furnishes.
+
+### Each Class I or Class I-V enclosure shall be furnished with a thermostatically controlled electric heater sized for [[parameter: site-ambient-temperature-minimum]], a thermostat set to hold the interior not lower than 40°F, and a heater circuit terminated in a junction box on the enclosure.
+
+### The branch circuit to each heater shall be a dedicated circuit with ground-fault protection and a disconnecting means within sight of the enclosure, meeting NFPA 70 for a wet location.
+
+### The low temperature alarm at each heated enclosure shall be as indicated in the datasheet.
+
+```datasheet
+label: Heated Enclosure Low Temperature Alarm
+type: select
+options:
+ - "None"
+ - "Local indicator light on the enclosure"
+ - "Dry contact to the building automation system"
+default: "None"
+```
+
+### No alarm is the norm and leaves the heater unsupervised, so a tripped breaker is found by the frozen assembly in spring. A local light tells a passer-by the heater has power, which is as far as it goes. A dry contact to the building automation system tells someone indoors the enclosure has gone cold while there is still time to drain or heat it, and suits a service the building cannot lose. {note}
+
+### Each enclosure shall be set on a concrete pad furnished under [[sync/concrete-pads]], extending not less than 4 in. beyond the enclosure on each side, with the enclosure anchored to the pad as its listing requires and the gap between enclosure and pad sealed against the entry of water and rodents.
+
+### Each enclosure shall be sized so that the assembly can be installed at the height and with the clearances this standard requires, and so that a tester can reach every test cock with the enclosure open.
+
+### Piping entering and leaving an enclosure shall be insulated and heat traced from the frost line to the enclosure wall where [[parameter: site-ambient-temperature-minimum]] is below freezing, with the heat tracing furnished under [[sync/electric-heat-tracing]].
+
+## Below-Grade Vaults {toc}
+
+### A vault shall be used to house an assembly only where [[drawing: the plumbing plans]] indicate one and where the water purveyor's program permits the assembly type in a vault.
+
+### A reduced pressure principle assembly, a reduced pressure detector assembly, a pressure vacuum breaker assembly, and a spill resistant vacuum breaker assembly shall not be installed in a vault or pit.
+
+### A vault floods, and an assembly whose relief valve or air inlet sits in standing water has lost its protection; the codes and every purveyor program confine vaults to double check types, whose checks keep working submerged, and most programs discourage even those. {note}
+
+### Each vault shall be drained by gravity to daylight or, where no gravity drain is possible, by a sump pump with a high-level alarm to the building automation system, and shall be kept free of standing water at the elevation of the assembly.
+
+### Each vault shall have a lid that can be opened by one person, a ladder or steps, and the clearances this standard requires around the assembly, and shall be sized so that the assembly can be tested and have its check modules removed from inside the vault.
+
+### Where a vault is installed in a freezing climate, the assembly shall be below [[parameter: frost-depth]] or the vault shall be insulated and heated as a Class I enclosure.
+
+# Field Testing and Certification {toc}
+
+## Tester Engagement and Test Equipment {toc}
+
+### The initial certification test of each assembly shall be performed by the tester indicated in the datasheet.
+
+```datasheet
+label: Initial Certification Test Performed By
+type: radio
+options:
+ - "Certified tester engaged by the Contractor"
+ - "Certified tester engaged by the Owner"
+ - "Water purveyor's tester"
+default: "Certified tester engaged by the Contractor"
+```
+
+### A tester engaged by the Contractor is the norm and puts the test inside the construction schedule and the Contractor's responsibility for a failed result. An Owner-engaged tester is the Owner's own cross-connection contractor, who will test the assembly every year after and knows the purveyor's forms; the Owner's schedule then governs when the water is turned on. A purveyor's tester is used where the purveyor tests its service connections itself and accepts no other report. {note}
+
+### Where the tester is engaged by the Owner or the purveyor, the Contractor shall give not less than five working days' notice that an assembly is ready for test, and the cost of the first test of each assembly shall be borne by the party engaging the tester.
+
+### Each test shall be performed with a differential pressure test kit calibrated within the interval indicated in the datasheet, and the calibration certificate number shall appear on the test report.
+
+```datasheet
+label: Test Kit Calibration Interval
+type: range
+unit: months
+options:
+ min: 3
+ max: 12
+ setpoints: [3, 6, 12]
+default: 12
+```
+
+### Annual calibration is what the USC Foundation and most purveyor programs require of a test kit; a program may require a shorter interval, and a kit that has been dropped is out of calibration whatever its certificate says. {note}
+
+### Where the purveyor's program requires a calibration interval shorter than the datasheet value, the program's interval shall govern.
+
+## Initial Certification Test {toc}
+
+### Each assembly shall pass an initial certification test after it is installed and before water is supplied through it to any outlet, equipment, or system.
+
+### The test shall follow the field test procedure the purveyor's program requires, and where the program names none, the procedure published in the USC FCCCHR Manual for the assembly type.
+
+### The test shall verify, as the procedure for the assembly type requires, that each check valve holds tight in the direction of flow, that the relief valve of a reduced pressure type opens at not less than the differential its listing requires, that the air inlet of a vacuum breaker type opens at not less than the pressure its listing requires, that the shutoff valves hold, and that the detector bypass of a detector type registers flow.
+
+### A new assembly fails its first test more often than any later one, because the debris of a new service lodges in a check, a shutoff valve seat was damaged in handling, or the assembly was installed in an orientation it was not approved in; the test is what finds those before the water is on. {note}
+
+### The initial certification test of an assembly on domestic water shall be performed after the piping it serves has been flushed and disinfected under [[sync/disinfection-of-water-systems]] and before the piping is returned to service.
+
+### No assembly shall be removed, bypassed, or left open during flushing or disinfection, and the assembly serving a disinfected segment shall be confirmed in place and operable before that segment is returned to service.
+
+### The initial certification test of a fire service assembly shall be performed in coordination with the forward-flow test and the acceptance test of the sprinkler system, so that the assembly is tested at the sprinkler system demand.
+
+### Where an assembly fails its initial test, the Contractor shall repair or replace it with listed parts for the model, retest it, and bear the cost of the repair and the retest.
+
+### Where the parties disagree whether a test result constitutes a failure, the Engineer of Record shall make the initial determination, and the purveyor's program shall make the final one for any assembly it regulates.
+
+### Where the design flow can be produced during the initial test, the Contractor shall measure the pressure loss across each premises isolation assembly and each fire service assembly at the test cocks and shall report any value above the maximum loss this standard sets to the Engineer of Record.
+
+## Repairs and Replacement Parts {toc}
+
+### Each repair to an assembly, during construction or under warranty, shall be made only with the assembly manufacturer's parts for the model and size, by a repairer the purveyor's program accepts.
+
+### An assembly is listed and approved as the sum of its parts, and a check module, spring, or relief diaphragm from another model, or a generic elastomer, makes it an unlisted assembly whatever its test result; the purveyor's program can require such an assembly to be replaced. {note}
+
+### Each repaired assembly shall be retested by a certified tester before it is returned to service, and the repair and retest shall be recorded on the test report.
+
+### Where a check module or relief valve is replaced, the removed part shall be delivered to the Owner or disposed of as the Owner directs, and shall not be reinstalled in any assembly on the project.
+
+## Owner Instruction {toc}
+
+### Before the assemblies are accepted, the Contractor shall demonstrate to the Owner's operating staff the location of each assembly, the operation of its shutoff valves and any bypass or parallel arrangement, the location and purpose of its test cocks and relief discharge, the operation of each enclosure heater and alarm, and the annual test date recorded on each tag.
+
+### The demonstration shall be scheduled with not less than five working days' notice and shall be recorded in the closeout submittals with the names of those attending.
+
+## Test Report and Filing {toc}
+
+### Each test shall be recorded on the form the water purveyor or the Authority Having Jurisdiction requires, and where neither requires a form, on a form giving every item below.
+
+### Each test report shall identify the property and the assembly location, the assembly type, manufacturer, model, size, and serial number, the installation date, the test date, the tester's name, certification number, and certification expiration, the test kit model, serial number, and calibration date, the recorded values of each test step, the pass or fail result, any repair made and the retest result, and the tester's signature.
+
+### The Contractor shall file each test report with the water purveyor and the Authority Having Jurisdiction within the time their programs allow, and within 10 days of the test where neither program sets a time.
+
+### A purveyor's program is enforced through its records, and an assembly that was tested but never reported is an untested assembly in the program's eyes, which can cost the Owner a notice or a shutoff a year later. {note}
+
+### A copy of each test report shall be left in the Owner's operation and maintenance data and a copy shall be attached to or kept at the assembly where the purveyor's program requires it.
+
+## Tagging and Annual Testing {toc}
+
+### After its initial certification test, each assembly shall carry the tester's tag or sticker that the purveyor's program requires, giving the test date, the result, and the tester's certification number.
+
+### Each testable assembly is required by the plumbing codes and by the purveyor's program to be tested again at least annually, and after any repair or relocation, for as long as it is in service; that testing is the Owner's obligation once the assembly is accepted, and the program may discontinue service to a premises whose assembly is overdue. {note}
+
+### The Contractor shall state, in the installed assembly schedule and on each assembly tag, the date by which the next test is due, which shall be twelve months from the initial certification test unless the purveyor's program sets a shorter interval.
+
+### Where the Contractor repairs or replaces an assembly under warranty, the Contractor shall have it retested by a certified tester and shall file the retest report as this standard requires for an initial test.
+
+# Delivery, Storage, and Handling {toc}
+
+## Each assembly shall be delivered in the manufacturer's packaging with its end caps, test cock plugs, and listing marks in place, and the Contractor shall inspect each assembly for shipping damage on arrival.
+
+## Assemblies shall be stored indoors, above freezing, out of direct sunlight, and off the floor, with their end caps in place until the connections are made.
+
+## An assembly stored with water in it and allowed to freeze is damaged before it is installed, and an assembly stored open collects the debris that fails its first test. {note}
+
+## An assembly that has been stored for more than 12 months before installation shall be inspected by the Contractor, and its elastomer checks and relief diaphragm shall be exercised or replaced as the manufacturer's storage instructions require.
+
+## Enclosures shall be stored on their pallets, protected from impact, with their hardware and heater components kept with them.
+
+## Assemblies shall be lifted by their bodies or by lifting lugs where furnished, and never by their shutoff valve handles, test cocks, or relief valve.
+
+# Warranty {toc}
+
+## The Contractor shall procure assemblies and enclosures carrying at least the warranty coverage indicated in the datasheet, and shall furnish evidence of that coverage in the closeout submittals.
+
+```datasheet
+label: Warranty Period
+type: range
+unit: yr
+options:
+ min: 1
+ max: 10
+ setpoints: [1, 2, 3, 5, 10]
+```
+
+## Where the datasheet indicates no warranty period, each assembly and enclosure shall carry the standard published warranty for its class, and the Contractor shall state that period in the closeout submittals.
+
+## The warranty period shall begin at substantial completion or at the date of beneficial use by the Owner, whichever is earlier.
+
+## The Contractor shall warrant the installation of each assembly and enclosure against defects in workmanship for one year from the start of the warranty period.
+
+## Where an assembly fails a certification test within the warranty period and the failure is attributable to a defect in the assembly or in its installation, the Contractor shall repair or replace the assembly, retest it, and file the retest report at no cost to the Owner.
+
+## The warranty shall not cover damage from freezing where the enclosure or heat was installed and operating as specified and the Owner interrupted its power, damage from debris admitted by the Owner's operation of a bypass, or wear of elastomer parts beyond the first year.
+
+## Where a warranted component is repaired or replaced, the repaired or replaced component shall carry a fresh full warranty term running from the date of the repair, or the remainder of the original term, whichever ends later.
+
+## The Contractor shall bear the cost of removing and reinstalling adjacent work required to reach an assembly being repaired under warranty, and shall restore that work to its recorded condition.
+
+# Spare Parts {toc}
+
+## The Contractor shall deliver the spare parts indicated in the datasheet to the Owner at substantial completion, each marked with the identifier of the assembly it serves and stored together in a labeled container in the location the Owner designates.
+
+- one complete rebuild kit for the first check and one for the second check of each reduced pressure principle and double check model and size installed
+- one relief valve rebuild kit for each reduced pressure principle model and size installed
+- one air inlet and check rebuild kit for each vacuum breaker assembly model and size installed
+- one set of test cocks for each assembly size installed
+- one heater element and one thermostat for each heated enclosure model installed
+- the special tools the manufacturer requires for removing the check modules of each assembly 2-1/2 in. and larger
+
+```datasheet
+label: Spare Parts Delivery
+type: checkbox
+options:
+ - "Check valve rebuild kits"
+ - "Relief valve rebuild kits"
+ - "Vacuum breaker air inlet and check rebuild kits"
+ - "Test cock sets"
+ - "Enclosure heater elements and thermostats"
+ - "Check module removal tools"
+default:
+ - "Check valve rebuild kits"
+ - "Relief valve rebuild kits"
+```
+
+## Spare parts shall be delivered in the manufacturer's sealed packaging marked with the part number, the models they fit, and the date of manufacture, and no elastomer kit older than two years at delivery shall be accepted.
+
+## The Contractor shall obtain the Owner's signed receipt for the spare parts delivered.