Val Pak 1 1 2" MPT Spring Return Line Check Valve (V20 339) pentairpool The 600890B is a practical The 600890B is a practical service part when a compatible Raypak heater needs an auto reset 14 B thermostat to restore dependable thermal control support The 25 square foot rating and 1 1 2 inch slip connection give this filter practical value because correct sizing and connection fit matter in preserving the intended flow and installation relationship of the system The Val Pak 1 1 2 inch MPT spring return line check valve is designed for compatible plumbing applications where one way flow control is needed on a return line This replacement is especially useful when the original valve has started sticking