No. 7 To 10 Universal Rubber Winter Plug for a Variety of 1-1/2 Inch Pipe Safely seal off in-ground plumbing lines during freezing conditions! Winter freeze plugs are used to plug your swimming pool pipes after they have been drained to prevent water from entering the pipes and causing freeze damage. The extra long taper allows for a more secure fit. Extended bolt for plugging deeper into pipes. Stainless steel bolts and washers. Large plastic wingnuts.