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How Much A Pool Evaporates?

Did you know evaporation is by far the largest source of energy loss for home or commercial swimming pools? When compared to evaporation, all other losses are small. The reason evaporation has such an impact is that evaporating water requires tremendous amounts of energy.


Evaporation has another effect that figures into your current concerns in this water conservation/drought conditions. In some areas the evaporation rates estimated that the entire volume of the pool, in gallons, is the amount of water evaporating and needing to be replaced in a year’s period of time.

The evaporation rate from an outdoor pool varies depending on the temperature of the pool, the temperature and humidity of the air, and the wind speed at the pool surface. The higher the pool temperature and wind speed and the lower the humidity, the greater the evaporation rate.

Since evaporation is the major source of heat loss for all swimming pools, to minimize evaporation one must cover the pool. Covering the pool with a pool cover when it is not in use is the single most effective means of reducing pool heating costs

Pool covers also provide many other benefits beside the tremendous energy savings. They conserve water by reducing the amount of make-up water needed by 30-50%. They can reduce chemical consumption by 35-60%. They also cut cleaning time by keeping dirt and other debris out of the pool.

It is highly recommended that the first step to cutting pool energy loss be the evaluation of the economics of using a swimming pool cover.

The Department of Energy had prepared a chart years ago that showed the cost savings for covering your pool with a pool blanket when not in use. The typical range for pools is 78°- 82° F. Keep in mind, however, that the energy consumption for each degree rise in temperature will cost from 10-30% more in energy costs depending on your location.

In warmer climates the percentage is higher due to the relatively low cost of heating a pool at 78° F. the chart below shows costs of heating pools in different parts of the country to different temperatures. The figures are based on a 1000 square foot outdoor pool heated with an 80% efficient natural gas heater at $.50 per therm. The pool is uncovered for 8 hours per day.

But if you don’t want the initial expense and lack of storage space for a pool blanket cover, technology has a liquid solar pool cover that you add to your pool water that will cover your pool surface when it is not in use and just needs replacing on average as once a month. When you look at the entire volume of your swimming pool being lost through the evaporation process in a year, putting a “lid” on your pool surface is a smart investment.