When placing a solar cover on the surface of a swimming pool, the bubbles side should go down. The bubbles are what cause the cover to float, so the solar cover can be cut to conform to the size of the pool and it can be placed directly on the water.
Normally, evaporation is the largest source of energy loss for an outdoor swimming pool. Solar covers reduce evaporation and help retain a pool's warmth despite evaporation and cooler night temperatures. They also save water, reduce the consumption of chemicals, and keep dirt, leaves and other debris out of the pool. For indoor pools, solar covers reduce evaporation and control humidity. The use of solar covers results in significant savings in energy costs. The covers should be removed just before swimming and replaced when swimming time is over.
Solar covers are lightweight and easy to put on and take off of a swimming pool. For covers of larger pools, motor-driven semiautomatic reels are available. These are either on carts or can be mounted directly onto the pool deck. The semiautomatic cover must be pulled when it is unreeled, and it must be guided back onto the reel when it is being wound up. Fully automatic covers are permanently mounted to the deck and wind or unwind at the touch of a button.