a device for use in winterizing inground swimming pools avoids the necessity of draining the pool in order to drain underground water - filled conduits before freeze - up . the device is an elongated cofferdam open at top and rear with a groove for receiving a sealant extending along the rear edge of side and bottom walls . the sealant , such as a denture adhesive , will hold the device against the pool side wall surrounding a water inlet , and so that the device opens above the water surface . water within the device and the conduit leading to the inlet is pumped therefrom and then a plug is inserted in the inlet to prevent pool water from entering the inlet after the device is removed from the pool side wall .