This 4 inch lead free reduced pressure zone assembly backflow preventer helps 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. Its compact modular design facilitates easy maintenance with a single access cover for in-line repairs. It is ideal for protection in continuous pressure piping applications and at cross-connections identified as health hazards and from other contaminants found at the service line entrance. This assembly consists of a short lay length stainless steel body, test cocks, corrosive resistant stainless steel bottom mounted relief valve, torsion spring check valves, and resilient seated gate valves with non-rising stem.