Natural Heating

• A swimming pool that is exposed to direct sunlight will increase in temperature to some extent without having anything special done to it. The larger and deeper the pool is, the less impact the rays of the sun will have on it due to the pool's thermal mass.The relative length of night and day in the location where the pool is will also determine whether one day's sun heating carries over to the next day or whether it is completely lost during the night.
  
  

Water Panels

• You can increase the rate at which the sun heats your pool by outfitting the pool with homemade solar hot water panels. You can build one of these by designing a sealed box with a glass top through which the water from the pool can be pumped in a grid of pipes. The water is heated as it runs back and forth in the pipe inside the box, and is then pumped back into the pool. Because the box is sealed, the temperature inside of it can get very high and the water will become quite hot as it flows through the pipes in the box.
  
  

Heat Trapping Covers

• The heat that is captured from the sun naturally by the surface of the pool and the heat that you introduce through solar hot water panels can both be prolonged in the pool by covering the pool at night with an insulated, waterproof blanket. You can make a simple pool covering out of a tarpaulin, or a more elaborate one using sheets of rigid foam cut to fit. This covering will prevent the heat from radiating out into the colder night air. It will also separate the water in your pool from cooling winds and breezes that would otherwise blow across the surface of the pool and suck the heat out of the water.
  
  

Orientation and Siting

• If you are in the process of building your own pool, you can maximize the amount of solar gain that your pool will get by orienting it advantageously in relation to the sun. This includes keeping the pool away from large buildings and trees that will shade it during the day and placing it on a south facing hillside where the microclimate will be warmest. Not placing it in areas that experience consistent winds and breezes will also help to keep the water warmer.