Journeyman Plumber ExamWater Supply SystemsMedium
A plumber is installing a water distribution system in a new commercial building with multiple water closets and urinals. The local code requires that these fixtures, if supplied directly from the water distribution system, must be protected against backflow. Which type of backflow prevention assembly is typically required for a direct connection to a flush valve-type water closet or urinal?
- AAtmospheric Vacuum Breaker (AVB)
- BReduced Pressure Principle Backflow Preventer (RPZ)
- CPressure Vacuum Breaker (PVB)
- DDouble Check Valve Assembly (DCVA)
Show answer & explanationAnswer & explanation
Correct answer: A. Atmospheric Vacuum Breaker (AVB)
Atmospheric Vacuum Breakers (AVBs) are commonly used for flush valve-type water closets and urinals. They prevent back-siphonage by introducing atmospheric air into the system when pressure drops, but they are not suitable for continuous pressure or backpressure conditions.
Why the other options are wrong
- B. RPZs are used for high hazard, continuous pressure, and backpressure applications, offering the highest level of protection, but are often overkill and more expensive for simple flush valves.
- C. PVBs prevent back-siphonage and can be under continuous pressure, but are typically for outdoor irrigation or similar and are not typically specified for flush valves due to code or specific fixture requirements.
- D. DCVAs are suitable for low hazard, continuous pressure applications, but not for high hazard flush valves.
Atmospheric Vacuum Breaker (AVB)
A backflow prevention device designed to protect against back-siphonage by opening to atmosphere when supply pressure drops, commonly used on flush valve fixtures.
- Protects against back-siphonage only
- Cannot be under continuous pressure
- Requires installation above flood rim
- Common for flushometer valves, hose bibs
Memory trick: AVB for the bowl, RPZ for the whole!