The 8'''' 450OSY Double Check Backflow Assembly, with OS&Y gate valves, is utilized in low health hazard applications for protection against both backsiphonage and backpressure of polluted water into the potable water supply. Shaped in the n-Pattern, the Model 450 is ideal for both new and retrofit installations in compact locations. The patented, center-stem guided Compound Check provides low headloss and reliable, superior performance. It also features a convenient single access cover to reduce maintenance downtime. Materials include a corrosion-resistant, epoxy-coated ductile iron body and access covers, and stainless steel fasteners and springs.