Watts Backflow Preventers: Models and Applications
Watts Water Technologies is one of the principal manufacturers of backflow prevention assemblies deployed across residential, commercial, and industrial water systems in the United States. This page covers the major Watts device families, their mechanical classifications, applicable hazard ratings, and the regulatory and installation contexts in which each assembly type is specified and tested. Matching the correct Watts model to a given application requires aligning device type, pressure range, and hazard classification with the cross-connection control requirements enforced by local water authorities and adopted plumbing codes.
Definition and scope
Watts backflow prevention assemblies are mechanical devices designed to protect potable water supplies from contamination caused by reverse flow events at cross-connection points within a distribution or plumbing system. Two physical mechanisms drive backflow: backpressure, in which downstream pressure exceeds supply pressure and forces water backward, and backsiphonage, in which a negative pressure event in the supply line creates a siphoning effect. Both mechanisms are addressed in the USC Foundation for Cross-Connection Control and Hydraulic Research (USC FCCCHR) Manual of Cross-Connection Control, which defines the performance thresholds that listed assemblies must meet.
Watts assemblies are tested and listed under the USC FCCCHR program and are manufactured to conform to standards published by ASSE International — the primary standards body for plumbing safety devices in the US. Relevant ASSE standards governing Watts product classifications include ASSE 1013 (Reduced Pressure Zone assemblies), ASSE 1015 (Double Check Valve assemblies), ASSE 1020 (Pressure Vacuum Breakers), and ASSE 1001 (Atmospheric Vacuum Breakers). Watts assemblies also carry listings under the International Association of Plumbing and Mechanical Officials (IAPMO) and are referenced in cross-connection control programs administered by water utilities under EPA Cross-Connection Control guidelines.
The Watts backflow prevention product line covers four primary assembly classifications:
- Reduced Pressure Zone (RPZ) assemblies — for high-hazard cross-connections where contamination risk is severe
- Double Check Valve assemblies (DCVA) — for low-hazard applications where contaminants pose no direct health threat
- Pressure Vacuum Breakers (PVB) — for irrigation and other systems not subject to continuous downstream pressure
- Atmospheric Vacuum Breakers (AVB) — for point-of-use protection in low-complexity, non-continuous-pressure scenarios
The backflow-listings catalog for the Watts brand spans devices rated for working pressures up to 175 psi across most assembly types, accommodating commercial and light industrial service conditions.
How it works
Reduced Pressure Zone assemblies — represented in the Watts line by the Series 909 and Series LF009 — use two independently acting check valves separated by a reduced pressure zone chamber. A differential relief valve vents that chamber to atmosphere if either check valve fails or if downstream pressure approaches supply pressure. This redundancy qualifies RPZ assemblies for high-hazard installations under ASSE 1013. The Series 909 is available in sizes from ¾ inch to 10 inches, accommodating everything from domestic service connections to large commercial mains.
Double Check Valve assemblies — including the Watts Series 007 and Series LF007 — contain two independently acting spring-loaded check valves in series. No relief valve is present. Because these devices cannot vent a contamination event to atmosphere, they are restricted to low-hazard applications under ASSE 1015. The Series 007 is among the most widely installed double check assemblies in the US for fire suppression system isolation and non-toxic fluid services.
Pressure Vacuum Breakers — such as the Watts Series 800M4QT — incorporate a spring-loaded check valve and an independently operating air inlet valve. The air inlet opens under negative pressure conditions, breaking any siphon before backsiphonage can occur. PVBs are approved under ASSE 1020 and are suitable for irrigation systems, provided the device is installed at least 12 inches above the highest downstream outlet, as required by the Uniform Plumbing Code (UPC) Section 603.
Atmospheric Vacuum Breakers operate without a test port and function only when the supply valve is closed. They are the least protective classification and are restricted to very specific point-of-use applications under ASSE 1001.
Common scenarios
Watts RPZ assemblies (Series 909 and LF009 variants) are commonly specified for:
- Boiler and hydronic heating systems where chemical additives create high-hazard cross-connections
- Medical and laboratory facility water supplies
- Commercial irrigation systems connected to reclaimed or chemically treated water sources
- Fire sprinkler systems where antifreeze or other additives are present
Watts Double Check assemblies (Series 007) are commonly deployed for:
- Residential and light commercial irrigation systems using potable water only
- Commercial food service equipment connections classified as low-hazard by the authority having jurisdiction
- Fire suppression systems using water only, where the hazard classification is low
Watts PVBs are most frequently installed on residential irrigation systems where continuous downstream pressure is not maintained. The backflow-directory-purpose-and-scope page provides context on how device selection intersects with utility-mandated cross-connection control programs at the municipal level.
Permitting and inspection requirements vary by jurisdiction. Most water authorities require that backflow prevention assemblies be tested at initial installation and on an annual basis thereafter by a licensed backflow prevention assembly tester (BPAT). The how-to-use-this-backflow-resource page outlines how the directory is structured to support locating qualified testers by geography.
Decision boundaries
The critical decision boundary in Watts device selection lies between RPZ and DCVA classifications. The determining factor is hazard level — defined by the type of fluid or substance present downstream of the cross-connection.
| Assembly Type | Hazard Level | Continuous Pressure | Testable | Typical ASSE Standard |
|---|---|---|---|---|
| RPZ (Series 909) | High | Yes | Yes | ASSE 1013 |
| DCVA (Series 007) | Low | Yes | Yes | ASSE 1015 |
| PVB (Series 800M4QT) | Low–Moderate | No | Yes | ASSE 1020 |
| AVB | Low | No | No | ASSE 1001 |
RPZ assemblies are required wherever the downstream fluid could directly endanger health — a threshold defined by the authority having jurisdiction, typically a water utility or state health department, with reference to the AWWA Manual M14: Recommended Practice for Backflow Prevention and Cross-Connection Control. Substituting a DCVA for an RPZ in a high-hazard application is a code violation in jurisdictions that have adopted the Uniform Plumbing Code or the International Plumbing Code.
Lead-free material compliance is a separate decision boundary. Watts LF-prefix models (LF009, LF007) are manufactured to meet the lead-free requirements of the Reduction of Lead in Drinking Water Act (2011) and California AB 1953, which restrict wetted surface lead content to a weighted average of 0.25 percent. Jurisdictions with lead-free mandates require LF-series assemblies in all potable water service applications.
Size selection follows hydraulic demand calculations — specifically pressure loss across the assembly at peak flow. Watts publishes head loss tables for each model series; specifiers reference these against available supply pressure to confirm that the assembly will not reduce residual pressure below the minimum required by the distribution system or fire protection design.
References
- U.S. Environmental Protection Agency — Cross-Connection Control Manual
- USC Foundation for Cross-Connection Control and Hydraulic Research (USC FCCCHR)
- ASSE International — Plumbing Safety Standards
- IAPMO — International Association of Plumbing and Mechanical Officials
- AWWA Manual M14: Recommended Practice for Backflow Prevention and Cross-Connection Control
- EPA — Use of Lead-Free Pipes, Fittings, Fixtures, Solder, and Flux for Drinking Water
- Uniform Plumbing Code (UPC) — IAPMO Publication