A double check valve or double check assembly (DCA) is a backflow prevention device designed to protect water supplies from contamination. It consists of two check valves assembled in series usually with a ball valve or gate valve installed at each end for isolation and testing. Often, test cocks (very small ball valves) are in place to attach test equipment for evaluating whether the double check assembly is still functional.

The double check valve assembly is suitable for prevention of back pressure and back siphonage, but is not suitable for high hazard applications. It is commonly used on lawn irrigation, fire sprinkler and combi-boiler systems.

See also

• Air gap
• Hydrostatic loop
• Pressure vacuum breaker
• Chemigation valve
• Reduced Pressure Principle BFP
• Atmospheric vacuum breaker
• Reduced pressure zone device