Double check valve assembly (DC)
A testable backflow prevention assembly consisting of two independently acting spring-loaded check valves, used for non-health hazard applications.
A double check valve assembly, often shortened to DC or DCVA, consists of two independently acting, spring-loaded check valves mounted in series inside a single body or pair of bodies, with a shutoff valve on each end and test cocks for field testing. Each check is designed to close tightly on its own, so the assembly provides redundancy: if one check fouls or wears, the other still stands between the downstream system and the potable supply.
The DC protects against both backpressure and backsiphonage, but because it has no relief valve and no way to discharge captured water, it is approved only for non-health hazard connections, where the worst outcome of a failure would be aesthetically degraded water rather than illness. It is widely used on fire sprinkler services without chemical additives, on irrigation connections in some jurisdictions, and on other low hazard equipment where an RP would be more protection than the risk requires.
Testers and property owners should remember that a DC gives no outward sign of internal failure. A fouled check can sit undetected for a long time because nothing discharges and flow continues normally, which is exactly why periodic differential testing exists, typically annual where required, set by the water authority. Owners should also confirm with the purveyor that the hazard is still classified as low; a change in downstream use can make an upgrade to an RP necessary.
Related terms
| Reduced pressure principle assembly (RP) | A testable backflow prevention assembly using two independently acting check valves with a pressure differential relief valve between them, suitable for high hazard applications. |
| Check valve | A valve that allows water to flow in one direction and closes to prevent flow in the reverse direction. |
| Detector assembly | A backflow prevention assembly for fire service lines that includes a metered bypass to detect low flows such as leaks or unauthorized water use. |
| Annual testing | The periodic field testing of backflow prevention assemblies, typically annual where required, set by the water authority, that verifies each assembly still works. |
The three-year clock sheet
One printable page: every 5000-series requirement, the recert timeline counted back from your expiry date, and the kit checklist. Free.
No spam. One useful sheet and occasional certification notes.