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Double Check Valve: Definition & Technical Guide

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A double check valve assembly (DCVA) is a backflow prevention device consisting of two independently operating spring-loaded check valves installed in series within a single body, with test ports between them for annual inspection. Double check valves protect potable water supplies from contamination by preventing both backpressure and back-siphonage in medium-hazard applications such as irrigation systems, fire sprinkler connections, and commercial plumbing.

Redundant Check Valves, Test Ports & Hazard Classification Limits

The double check valve provides redundant protection through its two-valve design. If the first check valve fails due to debris, wear, or corrosion, the second valve independently maintains the seal and prevents reverse flow. This redundancy makes the DCVA significantly more reliable than a single check valve, though it provides less protection than a reduced-pressure zone (RPZ) assembly, which adds a monitored relief zone between the checks.

Each check valve inside the assembly uses a spring-loaded disc or poppet that opens under forward flow pressure and closes automatically when flow stops or reverses. The springs ensure positive closure regardless of pipe orientation and create a consistent seal even when the pressure differential across the valve is very small.

Between the two check valves, test ports allow a certified tester to verify that each valve is sealing independently and meeting the required tightness specifications. Annual testing is mandatory in most jurisdictions to ensure the assembly continues to protect the water supply. A failed test requires immediate repair or replacement of the internal components.

Double check valves are classified for moderate-hazard (non-health-hazard) cross-connections. High-hazard connections where contamination could cause illness or death require an RPZ assembly or air gap instead. The local water purveyor determines the hazard classification based on the nature of the connected system.

DCVA, Detector Assembly, Residential Dual Check & Lead-Free Types

Double check valve assemblies (DCVA) are the standard testable configuration with shut-off valves and test ports. These are installed on permanent connections and require annual testing.

Double check detector assemblies (DCDA) add a bypass meter that detects small, unauthorized flows through a fire sprinkler connection. These are specifically designed for fire protection system connections.

Residential dual check valves are smaller, non-testable versions installed at the water meter or service entrance. They provide basic protection but are not suitable for applications requiring testable assemblies.

Lead-free double check assemblies meet current Safe Drinking Water Act requirements with wetted surfaces containing no more than 0.25 percent lead by weight.

Installation, Annual Testing & Backflow Prevention Services

Bonded Plumbworks’ backflow prevention services include double check valve assembly installation. Common installation points include irrigation system connections, fire sprinkler supply lines, and commercial kitchen equipment connections. Each installation includes proper sizing based on the system’s flow requirements, shut-off valves on both sides, and accessibility for annual testing.

Annual backflow testing is a recurring service that Bonded Plumbworks provides for homeowners and commercial property managers. Test reports are filed with the local water authority as required by cross-connection control ordinances.

ASSE 1015, USC Approved List & Cross-Connection Control Requirements

ASSE 1015 establishes the performance standard for double check valve assemblies. The USC Foundation for Cross-Connection Control maintains the approved list of DCVA models. The applicable state building codes and local cross-connection control programs specify where DCVAs are required and mandate annual testing by certified testers.

Watts Series 007, Febco 850 & Apollo 4N-200 Product Examples

Watts manufactures the Series 007 and 007M1 double check assemblies for residential and commercial applications. Febco (Watts) produces the Series 850 DCVA. Wilkins (Zurn) offers the 350 series. Apollo produces the 4N-200 series lead-free double check valves.

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