Backflow Prevention
Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
Showing changes from Rev 3
to Rev 4
in Backflow Prevention.
---
title: Backflow Prevention
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### 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
…8 unchanged lines
```
−### 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.
−
### The tester's credentials shall be current at the time of testing — an expired credential invalidates the test.
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### Cross-connections are classified by the degree of hazard the non-potable source represents to the public health. {note}
−```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"
−```
−
### 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}
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### 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
…27 unchanged lines
| 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
…12 unchanged lines
```
+### The application of each backflow assembly — premises isolation, in-plant isolation, fire service, or irrigation — shall be specified.
+
```datasheet
label: Application
…8 unchanged lines
```
+### The service line size at each backflow assembly location shall be specified.
+
```datasheet
label: Service Line Size
…27 unchanged lines
### 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
…7 unchanged lines
```
+### The listing standards required for the RPZ assembly shall be specified for this installation.
+
```datasheet
label: RPZ Listing Standards
…18 unchanged lines
### 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
…7 unchanged lines
```
+### The listing standards required for the DCVA assembly shall be specified for this installation.
+
```datasheet
label: DCVA Listing Standards
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### 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
…7 unchanged lines
```
−### 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.
−
### The PVB shall not be used where back-pressure is possible.
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### 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
…5 unchanged lines
```
−### 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.
−
## Atmospheric Vacuum Breaker (AVB) {toc}
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### 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
…5 unchanged lines
```
+### 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
…7 unchanged lines
```
−### 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.
−
−### 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).
−
## 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
…6 unchanged lines
```
−### 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.
−
### DCAP assemblies shall not be substituted for an RPZ on any high-hazard or commercial-scale installation.
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### 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
…15 unchanged lines
### 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
…18 unchanged lines
## 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)
…5 unchanged lines
```
−## 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.
−
# 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
…33 unchanged lines
### Each assembly shall be installed with clearance on all sides sufficient to permit field testing, parts replacement, and inspection.
−### 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}
```datasheet
…9 unchanged lines
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.
…20 unchanged lines
### The indirect waste receptor for the relief discharge of every RPZ and RPDA-II assembly is governed by the following requirements. {note}
−```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 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
…8 unchanged lines
```
+### 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
…4 unchanged lines
```
−### 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.
−
−### 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]].
−
−### 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.
−
### 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}
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### 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
…5 unchanged lines
```
−### 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.
−
### Strainers are recommended on new-construction installations and on installations downstream of water main work where construction debris is likely. {note}
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### 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. {note}
+### Where a parallel bypass is not provided (the typical configuration), the Owner must accept water-service interruption during annual testing; testing typically takes 30 to 60 minutes per assembly.
# 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. {note}
+### Backflow prevention assemblies are best installed indoors in a heated mechanical space, because the internal mechanism — spring-loaded checks, relief valve diaphragms, air-inlet poppets — is damaged by freezing, and damage from a single freeze event is rarely repairable in place; the assembly typically must be replaced.
### 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.
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### 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
…6 unchanged lines
```
−### Every backflow prevention assembly installed under this scope shall be commissioned by a certified tester before the assembly is placed in service.
−
### 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.
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### 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
…11 unchanged lines
### The Engineer shall inventory every internal cross-connection on the project and specify in-plant backflow protection at each.
−### 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}
```datasheet
…12 unchanged lines
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}
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### 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
…8 unchanged lines
```
−### The Engineer shall account for the assembly pressure drop in the building's hydraulic calculation.
−
### 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}
…3 unchanged lines
### 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)
…5 unchanged lines
```
−### 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.
−
## Pressure Reducing Valve Coordination {toc}
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## 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.