The Principle Operation of a Pressure Vacuum Breaker Backflow Prevention Device Assembly

The Pressure Vacuum Breaker Backflow Prevention Device Assembly (PVB) is a mechanical backflow prevention method that provides protection against backsiphonage of non-potable water into a potable water system due a sub-atmospheric condition in the upstream piping system. It consists of a spring-loaded independent check valve, a spring-loaded independent air inlet valve, two resilient seated test cocks located upstream and downstream of the check valve and two resilient seated shut-off valves upstream and downstream of the PVB. The PVB is used for indirect cross-connections and is designed to prevent a backflow backsiphonage situation only. The PVB can be installed to control high and low hazardous cross-connection situations. The PVB is NOT designed to control backflow backpressure and should not be used where there is a possibility that backpressure would develop. However, the PVB can operate under continuous or intermittent pressure conditions meaning that the PVB can retain pressure when in a static state condition. Therefore, downstream shut-off valves can be utilized without compromising the integrity of the backflow prevention device assembly. Maximum working water pressure is 150 psig and the operating temperature is in the range of 33 degrees F to 180 degrees F. The PVB comes in sizes ranging from ½ inch 2 inches. The PVB shall comply with the American Society Sanitary Engineering 1020 Standard.