What is the best way to close off the return line ? The 1-1/2" fitting is a OD threaded all one piece with gaskets & fittings that screw on either side of the pool wall. After I remove the directional ball can I screw on a pvc threaded cap or do I need an expanding rubber plug? I live in the Central PA & winters can be unpredictable and can be mild, freezing rain or snow.