Pentair R172288 - 1.5 in or 2 in In Line Check ValveThe Pentair R172288 1. 5 in or 2 in In Line Check Valve is an important part of your plumbing system if it contains a chlorine feeder and heater. The Check Valve will prevent and check the back flow of chemicals to your pool or spa equipment to prevent any damage or corrosion due to the chemicals eating away at the equipment containing metal parts. Check back flow of chemically treated water Corrosion resistant and heavy duty material 1 1 2" female