The biggest cause of heat loss from a swimming pool is evaporation. A number of factors contribute to evaporation in your pool – air temperature compared to the water temperature, humidity level and the amount of wind blowing across the surface of the pool. The bigger the difference between the air temperature and the water temperature in a pool, the greater the evaporation and therefore the greater the heat loss. The same for low humidity environments, the potential for evaporation is increased when the humidity is low. When the wind is blowing across the surface of the pool, you increase the amount of evaporation and therefore heat loss.
If you are spending money to heat your pool, the last thing you want to do is throw that money down the drain… So invest in a good quality pool cover, and you’ll see the difference straight away! The pool cover will create a barrier between the wind and the water surface, and can also stop up to 99% of evaporation! A cover with good thermal properties will also stop heat loss through the fabric.
There are some different types of covers ranging from chemicals that coat the water surface, to floating rings to proper fabric covers. The chemicals and rings are not as effective as good quality fabric cover that is fully waterproof and covers the whole surface of the pool in one piece. The chemical style evaporates away by itself and needs to be continually added to be of any benefit. Rings – while they look cute, and (individually) stop evaporation, they are really not a practical solution as they leave lots of gaps which allow leaves and debris to fall through to the pool water. These eventually sink to the floor of the pool and need to be cleaned up by a pool vacuum or automatic pool cleaner. If you use a one piece fabric cover, it will help keep the leaves out of the pool as well as stop heat loss. Most fabric covers can be used in conjunction with a pool reel system to make covering and uncovering easier.
So if your main goal is to stop your pool from losing heat overnight, the best thing you can do is invest in a good quality, thermal pool cover.