The 4" 475DAV Reduced Pressure Detector Backflow Assembly, with OS&Y gate valves, is utilized in high health hazard, fire protection applications for protection against both backsiphonage and backpressure of contaminated water into the potable water supply. The 475DAV is shaped in the z-Pattern and installed vertically in a flow up orientation. It includes a small footprint for quick and easy fire protection retrofit applications, as well as a metered bypass system to detect leaks and any unauthorized water use, saving you valuable time and money on repairs and maintenance costs.