What is the difference between a double check valve backflow preventer and a reduced pressure zone backflow preventer (RPZ)? Where is one used versus the other?
Double check valve backflow preventers contain two independent check valves in one housing. Test cocks are located at strategic points so that the check valves can be tested with a backflow preventer test kit. Double check valves are used for non-health hazard cross connections in continuous pressure applications.RPZ backflow preventers include two check valves like a double check backflow preventer, but they also have an intermediate relief valve that opens to atmosphere if both check valves should fail. Because of this extra measure of protection RPZ backflow preventers are used in cross connections subject to backpressure or back siphonage where there is a potential health hazard in continuous pressure applications.
