Spill-Resistant Pressure Vacuum Breaker Backflow Prevention Device Assembly – Backsiphonage Condition – Check Valve Not Drip Tight
If a backflow backsiphonage were to occur in the inlet or supply piping with the downstream and upstream shut-off valves open, and the check valve was not drip tight because of debris, disk or seat failure, the air inlet valve would open to the atmosphere breaking the vacuum and terminating the backsiphonage situation between the potable and non-potable water system. The air inlet valve opens because the external force on the air inlet valve is greater than the internal force of the air inlet valve. The external force acting on the air inlet valve is the air inlet valve spring, which shall be no less than 1.0 psi. With the air inlet valve and check valve opened, air is pulled into the air inlet valve breaking the vacuum and preventing the siphoning of non-potable water into the potable water system, under a backsiphonage condition. The SRPVB is providing protection even though the check valve is not drip tight. If the air inlet valve did not open, under a backflow backsiphonage condition, the device would not offer protection. For these reasons, a certified tester should test the SRPVB at least annually.
