BigXwell Heavy-Duty Solar Pool Cover 7x7ft - 16Mil Blue

Warm water evaporates, and in a basement that vapor has nowhere to go. A floating blanket lies on the water itself, under the tub’s main cover, so less water leaves the tub in the first place. This one is a blue polyethylene bubble sheet, 16 mil thick and 7 × 7 ft (2.13 × 2.13 m), sold as a solar cover – indoors the sun plays no part, and the sheet simply works as a lid on the surface.

It is an extra layer, not a cover. The main cover still goes on top, and the sheet comes out completely before anyone gets in – never soak with it in the water. The listing makes energy claims without numbers, so expect a helper, not a fix for a worn-out cover.

Tip: Bubble sheets are usually laid bubble side down and cut with scissors. Trim a little at a time around the shell – a sheet that is slightly too big can be cut again, one that is too small cannot be fixed.