Pressure Vacuum Breaker Backflow Prevention Device Assembly – No Flow or Static State
If the downstream shut-off valve is closed and the upstream shut-off valve is open and no water is flowing through a pressurized PVB a static state within the body of the PVB exists. In a static state with the PVB pressurized, the check valve is closed and the air inlet valve is closed. The air inlet valve is held closed by supply pressure and the air inlet valve spring is trying to keep the air inlet valve open. The water pressure downstream of the check valve is less than the supply pressure. The differential pressure across the check valve is based on the tensile strength or loading of the check valve spring which shall be at least 1.0 psi.
