This Colt(TM) 3 inch double check detector backflow preventer assembly is designed to prevent the reverse flow of fire protection substances and water of non-potable quality from being pumped or siphoned into the potable water supply due to backsiphonage and or backpressure in accordance with national plumbing codes and water authority requirements. It is ideal for protection at cross-connections identified as non-health hazards such as on fire sprinkler systems and from other contaminants found at the service line entrance. This compact modular design with a single access sleeve for easy maintenance is approved for horizontal or vertical installation in accordance with the direction of the flow arrow on the assembly. It consists of a stainless steel body, tri-link check valves, outside stem and yoke resilient seated gate valves, UL Listed tamper switch, and four test cocks. It comes furnished with a gallon per minute meter to detect underground leaks and unauthorized water use.