Double Detector Check Valve Assemblies - Model


Double Detector Check Assembly

The Double Check Detector Valve Assembly (DCDA) is designed to prevent backflow in a fire water distribution system where there is a non-health hazard. It features a backflow preventer to stop the reverse flow of liquids caused by backpressure or backsiphonage. The assembly is suitable for fire protection applications, with a metered by-pass to detect leaks and other water use.

DCDAs can be installed in systems under continuous pressure service and may be subject to back pressure. In non-flow conditions, the check valves maintain a minimum of 1 PSI in the direction of flow. In flow conditions, the check valves open proportionally to the flow demand. In the event of backflow, the check valves will close until normal flow is resumed.

Dolor Sit Amet

  • Built to city and municipal specifications
  • Designed for use in fire protection and domestic feed lines
  • Factory pre-assembled and tested
  • Precast concrete vault and access hatchway
  • OEM top name components
  • Metered by-pass and OS&Y shut-off available

A Double Check Detector Valve Assembly (DCDA) is a device that is used to prevent backflow in a fire water distribution system. It consists of two independent check valves that are connected in series and a testable auxiliary valve. The DCDA works by allowing water to flow in one direction, while preventing it from flowing in the opposite direction.

When water flows through the first check valve, it opens and allows the water to pass through. When the water flow stops or reverses, the first check valve closes, preventing the water from flowing back. The second check valve works in the same way, providing an additional layer of protection against backflow.

In a non-flow condition, a double check detector valve, the check valves in the by-pass and mainline units are closed. Flows from 0 to 5 GPM will flow through the by-pass that contains a by-pass detector meter where unauthorized usage of water is recorded.

This operation at low flow rates is accomplished by designing the differential pressure drop across the by-pass line to be slightly less than the mainline check valve. Flows in excess of 5 GPM will open the mainline check valve for normal flow.

The testable auxiliary valve is used to test the proper functioning of the check valves. It allows the water to flow in the opposite direction to the normal flow for testing purposes.

In the event of a backflow condition, such as a sudden increase in the water pressure upstream, both check valves will close and prevent the contaminated water from flowing into the potable water supply. This ensures that the drinking water remains safe and clean.

Double Check Detector Valve Assemblies are available in a wide range of sizes and flow rates to suit different applications. The size and flow rate will depend on the specific requirements of the water distribution system it is being used in.

In general, DCDAs are available in pipe sizes ranging from 1/2 inch to 12 inches. The flow rate of a DCDA is measured in gallons per minute (GPM).

Size         Flow

2-1/2"   149 gpm
3"           230 gpm
4"           397 gpm
6"           900 gpm
8"         1559 gpm
10"      2458 gpm
12"      3525 gpm
Based on Sch 40 Pipe and 10 ft/sec

Double Check Valve Assembly (Zurn 350ADA)

Additional Resources

File Preview ⬎


Double detector for fire service


Backwater sewer valve


Detector check w/ post indic. valve & fire dept. connection


Fire department connection


Fire dept. connection & post indicator valve


Force main discharge manhole


Above ground enclosed reduced pressure assembly


Above gr. encl. N-pattern reduced pressure assembly


Above ground enclosed reduced pressure assembly


Concrete vault with hatchway


Air relief valve


BackFlo Flyer


Double check assembly, 3/4" through 2"


Double check assembly, 3" through 10"

Related Products