The 6'''' 350ASTDAOSYPI Double Check Detector Assembly with post indicator and OS&Y gate valves protects against both backsiphonage and backpressure in low health hazard, fire protection applications. Its stainless steel body, access covers, internals, fasteners, and springs are corrosion-resistant for reduced maintenance costs. Featuring a metered bypass system, the 350ASTDAOSYPI efficiently detects leaks and any unauthorized water use. Its single access cover reduces downtime and added costs associated with maintenance and repairs. The 350ASTDAOSYPI features a short lay-length for compact, versatile installation in horizontal or vertical positions.