0888820 (Watts) | 2-1/2 - 4 Inch | 774/774DCDA First Check Valve Repair KitThis 2 1 2 to 4 Inch First Check Detector Repair Kit For Series 774 And 774DCDA Prevents The Backflow of Fire Protection System Substances From Being Pumped or Siphoned Into The Potable Water Supply. This Kit Consists of a Complete Number One Cam Check With a Check O Ring. It is Designed For Installation on Applications Identified by Local Authorities as Non Health Hazard, Such as on Fire Protection Systems. Watts 0888820