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How much water evaporates from a pool?

Answer:

Water Evaporation from a Pool
The evaporation rate depends on the surface area of the pool, the temperature, and the relative humidity and the wind. I'm sure an "equation" containing the variables is known. Perhaps a civil or mechanical engineer would have a specific equation. I did find what seems to be a credible source that provides a reasonable answer. Here is the link: Marin municipal water district. They have a chart that lists 200-300 gallons per week for a medium-sized pool -- about 2%-5% of typical pool volumes. "Splash-out" water is probably a much more significant source of water loss.

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In my 14 years of experience, I found that there are a lot of circumstances involved in how much water is lost during evaporation. The best way to find out how much water your pool is losing is the following: Take a 5-gallon bucket and make a mark with a permanent marker at about the halfway point. Fill the bucket with water up to that point, and set the bucket right beside your swimming pool. Simultaneously, use a pencil to mark the water level on your pool tile. In that way, your can determine how much water has evaporated from the bucket and from the pool.
The evaporation rate of water from a swimming pool is fairly easy to calculate; given you have access to a psychrometric chart or a water vapor tables. W=(A (69.4+30.8 (V)) / Y )(Pw-Pa) W = lb / hr of evaporation. A = surface area of the swimming pool. V = mean wind velocity (mph). Y= Latent heat (approx. 1000). Pw - Sat. Vapor Press at water temp (in Hg). Pa - Sat. Vapor Press at room air temp (in Hg)
A simple rule of thumb in the pool industry is that 1/2" to 1" per day is normal evaporation. Evaporation more than 1" per day would indicate a considerable amount of splash-out or a water leak.
In different areas the rate of loss varies, but in Houston, Texas, we figure on evaporation of 1" to 1.5" per week during the summer.
Some people don't realize that water evaporation is much greater in the fall than in the summer -- when water temperatures are high and air temperatures are cold (especially at night). This will just suck the water right out of the pool.
I am sure there are a lot of variables regarding geographic location and humidity levels. In the Mid-Atlantic, I would consider anything over 1/2" per day the mark to start looking for problems (unless you have a heated spa or waterfall, etc.).

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Contributor:

Crystal

First answer by ID1166618412. Last edit by Joao Antonio Oliveira. Contributor trust: 18 [recommend contributor ]. Question popularity: 318 [recommend question].

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Relevant answers:

How much water evaporates from a pool in phoenix AZ?
Eventually, all of it if not replenished. The rate of evaporation depends on local climatic conditions.
How much water evaporates in a week from a swimming pool?
It depends on the surface size, temperature of the water and outside air temperature, the activity in the water, if there are any water features in the pool etc.
How much water evaporates from a swimming pool per day?
This depends on the surface area of the pool but generally speaking on a really hot day with a pool that is heated to 85F you can loose up to 1/4 inch of water a day.
How much water in pool that's 15ftx30ft?
I belive that's close to 80,000 liters
How much water is in a pool?
depends on the size of the pool