3/4" Pressure Relief Valve Piston-Type Pressure Relief/Regulating Valves. Bypasses excess liquid. Adjustable to maintain control of line pressure at any pressure within the valve''s operating range. Selected pressure setting firmly held in place by locknut. Extra large valve passages to handle large flows. Model 23120 302 stainless steel spring and EPDM O-ring. Excellent chemical resistance. 1/4" port for pressure gauge pipe plug included.