Double Check Valve Assembly (DCVA)

Technical Specification

CSA Standard

CSA B64.5 — Double Check Valve Assemblies

Also listed as

ASSE 1015 (US)

Protection Level

Moderate — protects against both backpressure and back-siphonage

Hazard Classification

Moderate-hazard (non-health-threatening) connections

Testing Frequency

Annual

Installation

May be installed below grade or in a vault; no relief valve discharge to accommodate

CSA B64.5 — Canadian Standards Association; ASSE 1015 — American Society of Sanitary Engineering

---

How the DCVA Works

The DCVA contains two independently operating spring-loaded check valves in series. Each check valve opens under normal supply pressure and closes if downstream pressure equals or exceeds supply pressure (backpressure condition) or if supply pressure drops below atmospheric (back-siphonage condition).

Because the two check valves operate independently, both would have to fail simultaneously for backflow to occur — providing meaningful redundancy for moderate-hazard applications. Unlike the RPZ, the DCVA does not have a relief valve and therefore cannot protect against severe-hazard connections where both check valves failing simultaneously would represent an unacceptable risk.

Check valve components degrade silently over time. A DCVA that shows no external sign of failure may have check valves that no longer hold the required differential pressure. Annual field testing with a calibrated gauge is the only way to confirm that each check valve remains functional.

---

Required Applications

• Multi-unit residential buildings (5+ units) — Main service connection; system water presents a moderate cross-connection hazard
• Office buildings — Standard commercial water service connections
• Retail commercial properties — Non-food-service commercial water service connections
• Fire suppression systems (without antifreeze or additives) — Fire system water that has been in the system is non-health-hazard; DCVA or DCDA used
• Hotels (service connection only) — Where commercial kitchen and severe-hazard connections are separately protected
• Light industrial without chemical connections

Note: If a building has mixed uses where one connection requires an RPZ, the water authority may require the entire main service connection to be protected by an RPZ rather than a DCVA.

---

Testing Procedure

DCVA testing verifies that each check valve holds under the specified pressure differential. The tester connects a differential pressure gauge to the test cocks and performs a differential pressure test on each check valve individually. A passing test requires:

• Check valve #1: opens at supply pressure; holds at specified minimum differential (typically 1 psi / 7 kPa)
• Check valve #2: opens at supply pressure; holds at specified minimum differential
• Both shut-off valves are operational

---

DCVA vs. DCDA

A Double Check Detector Assembly (DCDA) — also called a Double Check Valve Detector Assembly — is used specifically for fire sprinkler system connections. It adds a bypass line with a small meter to detect leakage or unauthorized water use through the fire system. The backflow prevention mechanism is the same as the DCVA.

---

Frequently Asked Questions — DCVA