Register Now Evaporation Index Calculator

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Wind shelter:

Water movement:

Pool evaporation is primarily effected by four factors: Water temperature, Dew point temperature, Air pressure, and the movement of air in relation to the water surface.

The variables that contribute to these factors can be classified into two different groups: Those that are weather related and those that are pool specific.

Weather related:
  • Dew point temperature
  • Air pressure
  • Wind speed
Pool Related:
  • Water temperature
  • Degree to which pool is sheltered from wind
  • Pool water movement

The Evaporation Index Calculator is meant to provide a single representative number which automatically accounts for these variables. When comparing this number from day to day or season to season, you should be able to account for weather related variability in evaporation observations at the same pool, or explain more clearly to a customer why their evaporation rate may be different from their neighbors pool.

While the number shown is indeed just an index, we have set it so that it approximates a factor of approximately 20 times what the actual water loss in inches would be in a "typical" pool if these weather variables remained constant for a period of 24 hours. Equivalently, this is about 8 times the amount of water loss in centimeters.

Index of 4.4 / conversion factor of 20 = .22" (0.55cm) of water lost to evaporation in 24 hours.

For the displayed index on your personalized home page we use weather information that is tied to the zip code you used to register on the site, and pool information that we deem "typical."

Our typical pool assumes a water temperature of 85° F and a solid fence or natural wind break surrounding the pool at about 20 feet from the pool edge. We also assume normal circulatory operation of a pool with no fountains, waterfalls or spillways. To account for special situations that may vary from this, try entering information into the calculator above.

Keep in mind also that the index is utilizing instantaneous weather conditions and that those conditions may not be consistent over an actual 24 hour period. For instance, wind is a very big factor in this calculation, and it is generally weaker at night than it is during the day. As a result the index as measured during the day may indicate a larger water loss than what would actually be experienced in an actual 24 hour period.

We hope that you find the Evaporation Index Calculator to be another valuable tool for providing professional leak detection and repair service to your customers. Please contact us with questions or comments.

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