Series 757DCDA, 757NDCDA Double Check Detector Assemblies prevent the backflow of pollutants that are objectionable but not toxic, from entering into the potable water supply. Compact housings consist of two independently operating tri-link check valves, two shutoff valves, and four test cocks. They feature a stainless steel housing and sleeve and are 70% lighter than traditional designs. Series 757, 757N is designed for non-health hazard applications and may be installed under continuous pressure service to protect against both backpressure and backsiphonage. This Series is used primarily on fire sprinkler lines when it is necessary to monitor unauthorized use of water. Maximum Working Pressure: 175psi (12.06 bar).