Spill-Resistant Pressure Vacuum Breaker Backflow Prevention Device Assembly – Flowing or Dynamic State
As water flows through a SRPVB with a demand downstream and the upstream and downstream shut-off valves open, the water pressure will force the spring-loaded air inlet valve to close. The air inlet valve spring is force loaded open. After the air inlet valves closes the water pressure will open the spring loaded check valve. The air inlet valve closes before the check valve opens because the spring loading keeping the air inlet valve open is less than the spring loading keeping the check valve closed. Since the check valve spring is forcing the check valve to close, the water pressure will have to overcome the force or loading of the check valve spring. This action decreases the water pressure to the amount equal to the tensile strength or loading of the check valve spring. According to industry standards, the check valve spring shall have a minimum force loading of 1.0 psi. According to industry standards, the air inlet valve spring shall have a minimum force loading of 1.0 psi. The flow rate through the SRPVB in gpm will have a factor on the extent the check valve will open. The greater the flow in gpm the greater the check valve will open.