Why Does Evaporation of Pool Water Happen?
Warm water with cold night air increases evaporation. On a very cold morning you will see fog rising from the pool.
You can lose 1/2" to 3/4" of water a day due to evaporation. The greatest evaporation rate can be in May and Sept/Oct in North America, when pool water can be in the 80's during the day and overnight air temps drop into the 70's.
Variations in wind intensity, humidity and sunlight can drastically change water loss rates. Some of the strongest and most intense wind in the country can be found in mountainous regions. The wind will undoubtedly have an effect on pool water, as wind can blow water particles and cause speedy evaporation. Other windy regions include the Great Plains, the Great Lakes and most coastal locations.
How to Reduce Evaporation in Pools
- Cover the pool. Research shows use of pool covers could reduce 95 percent of evaporation from California pools
- Reduce water temperature. Lower the thermostat on the pool heater. Reduce the difference between the pool water temperature and the nighttime air temperature.
- Add windbreaks around the pool. Landscaping, fences, or hedges can reduce the wind speed that hits the water surface.
I Am Losing Pool Water - Is it a Leak or Evaporation?
If your pool is only losing water in cooler months it is likely evaporation. We often see members thinking their pool sprung a leak when evaporation increases as the seasons change.
Follow a structured approach to leak detection as described in the TFP Leak Detection article The bucket test as described in that article should be your first step to determine if water loss is from evaporation or a leak.