What Is a Pressure Vacuum Breaker (PVB)?
A Pressure Vacuum Breaker (PVB) backflow preventer is a mechanical device that consists of one independently acting, spring-loaded check valve and an independently acting spring-loaded air inlet valve on the discharge side of the device. This device includes shutoff valves at each end of the assembly and is equipped with test ports. A PVB may be used to isolate health or non-health hazards but is only effective on back-siphonage conditions. Backpressure applications should be avoided. Normal applications would include isolation protection to an irrigation system and located at or near the exterior of a building. The PVB shall be installed 12 inches above the highest water outlet. During a back-siphonage condition (vacuum) the PVB will close the bottom check valve and the air inlet will open to let air enter the device to break the vacuum. This device is subject to failure as with anything mechanical, so annual testing is required.
