This 4 in reduced pressure zone 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 back siphonage and or backpressure in accordance with national plumbing codes and water authority requirements. This extremely compact and lighter than a traditional designed assembly is approved for horizontal N-pattern installation as long as the backflow assembly is installed in accordance with the direction of the flow arrow. 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 stainless steel body with a quick access sleeve, torsion spring check valves, grooved gear operated butterfly valves with tamper switch, test cocks, and a corrosive resistant stainless steel bottom mounted pressure relief valve.