A type of device used to prevent backflow in a water distribution system that consists of a spring loaded check valve, an independently operating air inlet valve, two resilient seated shutoff valves, and two resilient seated test cocks.
A backflow prevention device that introduces air into the system to prevent "back siphonage". Incorporates the use of a spring-loaded seat for positive opening to atmosphere. Will operate under constant pressure. Commonly used for high hazard application with no back pressure. The assembly must be installed at least 12 inches above all downstream piping and the highest downstream outlet.
A Pressure Vacuum Breaker (PVB) is a backflow prevention device, similar to an atmospheric vacuum breaker (AVB), except that the PVB contains a spring-loaded poppet and may be used on high hazard applications and may have valves installed downstream. Pressure vacuum breakers must be protected from freezing when installed outdoors.