What are some different types of backflow prevention assemblies, devices, and methods?

Types of Backflow Prevention

  • Air Gap (AG): An AG is a physical separation between the end of the discharge pipe and the flood level rim of the container being filled. The separation must be two times the diameter of the opening of the discharge pipe. This is the highest form of protection, since the drinking water supply is physically separated from the container.
  • Atmospheric Vacuum Breaker (AVB): An AVB is a non-testable device consisting of an air inlet valve or float check, a check seat and an air inlet port(s). This device is designed to protect against a non-health hazard or a health hazard under a backsiphonage only.
  • Double Check Detector Assembly (DCDA): The DCDA is a mechanical valve assembly consisting of two DCVAs, one that is line sized to provide full flow characteristics and one which is smaller (either half or three-quarter inches) located on a detector line. It is used for services having non-health hazards and under conditions of backpressure or backsiphonage, usually for fire suppression systems.
  • Double Check Valve Assembly (DCVA): A DCVA is a mechanical valve assembly consisting of two internally loaded, independently operating, check valves together with tightly closing resilient seated shut-off valves upstream and downstream of the check valves. It is used for services having non-health hazards and under conditions of backpressure or backsiphonage, usually for fire suppression systems.
  • Pressure Vacuum Breaker (PVB): A PVB is a mechanical valve assembly that includes a check valve, which closes with the aid of a spring when water flow stops. It also has an air inlet valve, which opens when the internal pressure exceeds atmospheric pressure, preventing backsiphonage. It is used for services having either health hazards or non-health hazards and no backpressure conditions; it is typically used on irrigation systems.
  • Reduced Pressure Detector Assembly (RPDA): The RPDA is a mechanical valve assembly consisting of two RPs, one that is line sized to provide full flow characteristics and one which is smaller (either half or three-quarter inches) located on a detector line. The RPDA is used on fire suppression systems which pose a health hazard.
  • Reduced Pressure Zone Assembly (RP): An RP is a mechanical valve assembly consisting of two internally loaded, independently operating, check valves and a mechanically independent, hydraulically dependent relief valve located between the check valves. It is used for services having either health hazards or non-health hazards and under conditions of backpressure or backsiphonage and gives the highest level of protection among the mechanical backflow prevention assemblies.

Show All Answers

1. What is backflow?
2. How can cross connections and backflow affect my drinking water?
3. What can I do to prevent backflow?
4. What is a backflow prevention assembly?
5. When is a backflow prevention assembly required?
6. What is a Certified Backflow Assembly Tester and how can I find one?
7. What does it cost to test a backflow prevention assembly?
8. What are some different types of backflow prevention assemblies, devices, and methods?
9. Do I need a permit to have a backflow prevention assembly installed and is there a permit fee?
10. Who can install a backflow prevention assembly?
11. What does it cost to install a backflow prevention assembly?
12. Why am I required to have my backflow prevention assembly tested?
13. How often do backflow assemblies need to be tested?
14. Who is responsible for the testing and maintenance of the backflow prevention assembly?