Short definition
A double check valve assembly (DCVA) is two independently-acting spring-loaded check valves in series, with a shutoff valve at each end and four test cocks for annual testing. Listed under ASSE 1015. Rated for low-hazard back-pressure and back-siphonage protection. In WA, the typical residential application is fire-sprinkler systems and some irrigation systems where the utility prefers a DCVA over a PVB.
What it is
The DCVA body contains two independent check valves arranged in series — water has to push through both to flow downstream, and reverse flow has to defeat both to come back upstream. Each check has its own spring, disc, and seat, so a failure of one doesn’t compromise the other. Two integral shutoff valves (one upstream, one downstream) allow isolation for testing and service. Four test cocks let a certified BAT verify each check during the annual test.
The two-check redundancy provides low-hazard back-pressure and back-siphonage protection. It does not provide the higher-protection central relief that an RPZ does, so DCVAs are not approved for high-hazard cross-connections.
A close cousin is the DCDA (Double Check Detector Assembly) — a DCVA with an additional bypass meter for detecting unauthorized water use on fire-sprinkler systems. Larger commercial fire systems typically use DCDA rather than DCVA.
Why it matters to a homeowner
DCVAs show up in three common WA residential / light-commercial applications:
- Residential fire sprinkler systems. WA jurisdictions generally require a DCVA at the supply tee feeding the sprinkler manifold.
- Some irrigation systems. Where the local utility prefers continuous-pressure protection over a PVB, a DCVA is the typical choice.
- Other low-hazard cross-connections classified by a certified CCS as needing DCVA-class protection.
Annual testing is required (see the entry on annual backflow test). Failed tests trigger repair (rebuild kit, $80–$250 plus labor) or replacement ($400–$1,500 depending on size). Most residential DCVAs are 1-inch or 1.5-inch and run on the lower end of the replacement range.
When you’ll encounter this term
- Residential fire sprinkler install — DCVA at the supply.
- Annual test letter from utility identifying a DCVA on the property.
- Failed annual test — plumber repair or replacement.
- Inspection report flags a DCVA with leaking test cocks.
Common variants and what it isn’t
- DCVA (residential / commercial isolation) vs. DCDA (Double Check Detector Assembly). DCDA has an additional bypass meter for unauthorized-use detection on fire-sprinkler systems. Both are double-check designs.
- DCVA vs. RPZ. DCVA is low-hazard with two checks; RPZ is high-hazard with two checks plus a central relief valve. RPZ is required for high-hazard cross-connections; DCVA is not.
- DCVA vs. PVB. DCVA is back-pressure-rated (and back-siphonage-rated); PVB is back-siphonage only.
Common failure modes
- Check disc / spring degradation — fails the reverse-flow test at annual.
- Test cocks leak at the seal during testing — testable but raises questions about device integrity.
- Mineral deposits at check seats — partial closure.
- Frozen body in unprotected exterior install — PNW winter problem when an exterior DCVA isn’t insulated or drained.
Washington note
WA DOH WAC 246-290-490 recognizes DCVA / DCDA as approved assemblies for low-hazard / non-health-hazard cross-connections. Annual testing by a certified BAT is required; results are submitted to the water utility. Hazard determination by a certified Cross-Connection Specialist (CCS) decides whether DCVA-class protection is sufficient or whether the application requires the higher-protection RPZ.
Specific WA jurisdictional preference between DCVA and PVB on residential irrigation varies — confirm with your local utility before specifying. Seattle, Tacoma, and Bellevue each maintain their own residential cross-connection program manuals.