Series C400, C400N, C400Z reduced pressure zone assemblies prevent the reverse flow of polluted water from entering into the potable water supply due to back siphonage and or backpressure. It consists of stainless steel body, sleeve and torsion spring check valves. Series C400, C400N, C400Z has a compact design that is 70 and #37; lighter than traditional designs, and is ideal for health hazard piping applications for protection against back siphonage or backpressure. Check with local water authorities for installation requirements. Maximum working pressure 175 psi.