Flush Threaded Winterizing Plug for PVC Pipe (1 1/2" Dia.) - HWP1022B Flush Threaded Winterizing plugs are use to safely seal swimming pool inlets and outlets. 1 1/2 inch diameter size (FIP) with flush turn knob. Heavy duty white ABS construction. EPDM O-ring is resistant to extreme weather and chemical corrosion Provides a positive seal with NO leaking