The R-K PBP series pressure bypass valve is a 3-port valve designed to relieve excess fluid pressure in piping systems. When mounted in-line, the pressure by-pass valve will permit fluid to pass through the system. When the fluid pressure approaches the valve setting, the excess fluid is vented through the bottom port. Adjustable screw and lock-nut makes it easy to accurately pre-set relief pressure. Wide working pressure range (10 to 80 PSIG) Top entry for easy in-line maintenance and can be factory pre-set upon request. No metal contact with fluid Note:This valve is not designed to be used in piping systems with back-pressure on the downstream side.