This 4 inch lead free double check valve backflow preventer assembly is designed to prevent the reverse flow of contaminated 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 hazard applications and from other contaminants found at the service line entrance. This compact and short lay length design with a single access cover for easy maintenance is approved for horizontal, vertical and retrofit installations. This assembly consists of a lightweight stainless steel body, outside stem and yoke resilient seated gate valves, spring loaded cam-check valves, and test cocks.