Waterway Check Valves have a clear lid and a bright seal flapper for easy inspection and access. The check valves have the spring/swing design to be used for both return and intake water. CPVC plastic bodies feature deeper sockets than others for better glue joints. Seal flapper is made of hi-tech thermoplastic polymer seal. Corrosion proof pin & stainless steel spring. Reversible flow. (Serviceable)