This Valterra 200-C15W check valve is made of clear schedule 40 (standard wall) PVC for corrosion resistance, high strength, and less weight than fittings made from metal. It is compatible with schedule 40 PVC (polyvinyl chloride) pipes and fittings or can be connected to other materials such as steel, copper, or cast iron using transition fittings. Its full flow design allows for insignificant flow loss at the swing check, so no spring is needed. It has 1-1/2" slip connectors at both ends to connect to pipes with a smooth bore for enhanced flow and has a maximum pressure rating of 150 psi. This check valve meets ASTM International and American National Standards Institute (ANSI) standards and is suitable for use with landscape and irrigation, pool and spa, aquaculture, and general purpose applications.Check valves have two ports and restrict the flow of fluids and other loose materials through a pipe or passageway to one direction. Flow enters through one port and exits through the other, closing when flow reverses or stops. Two common types of check valves are ball cone valves and swing check valves. A ball cone valve utilizes a spring-loaded ball seated against a cone-shaped interior surface to stop the flow of fluid in a forward direction, and a swing check valve has a movable disc on a hinge to block reverse flow. Check valves are rated by their cracking pressure (the minimum upstream pressure required for the valve to operate), and they are used in various water, gas, air, and steam lines. Valterra Products manufactures and distributes valves, hoses, sewer systems, and pool and spa products. The company, founded in 1981, is headquartered in Mission Hills, CA.