Spring Check valves are used to prevent back-flow and siphoning. The 1/2 lb. SS spring maintains a positive seal even when no backpressure is present. Suggested applications: pool/spa assemblies and installations, potable water systems. 2-psi minimum flow pressure required to open valve. Pressure rating: 150 psi, non-shock. water at 73 degrees F. Flow direction indicator molded into body for accurate installation. SS spring for corrosion resistance. Corrosion-resistant PVC body with EPDM seal.