This 4" lead free double check valve backflow preventer assembly is designed to prevent the reverse flow of 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 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 N pattern installation in accordance with the direction of the flow arrow on the assembly. It consists of a stainless steel body, tri-link check valves, non-rising stem resilient seated gate valves with grooved end connections, and test cocks.