The Apollo Model DC4SGLF Double Check Valve is designed to prevent contamination of the potable water supply due to back-siphonage or backpressure from substances that are non-health hazards. The modular check valves have replaceable seats and reversible EPDM seat discs. Grooved connections on an epoxy-coated ductile iron body allow for easy connection to butterfly valves or gate valves.lightweightshort lay lengthlow pressure lossmodular check valvesindividual access to check valvescorrosion resistant epxoy-coated ductile iron bodyUS patents lb5,711,341 and lb6,343,618made in the USA