This 6 IN double check detector backflow preventer assembly prevents the backflow of pollutants that are objectionable but not toxic, from entering into the potable water supply. Its compact housing consists of two independently operating tri-link check valves, two UL/FM butterfly shutoff valves, and four test cocks. It has a cubic foot meter. It features a stainless steel housing and sleeve and is 70 percent lighter than traditional designs. It is designed for non-health hazard applications and may be installed under continuous pressure service to protect against both backpressure and backsiphonage. It is used primarily on fire sprinkler lines when it is necessary to monitor unauthorized use of water. The maximum working pressure is 175 psi (12.06 bar).