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How To Prevent Swimming Pool Evaporation

Did you know that the number one way swimming pools lose water is through evaporation? According to the Department of Energy, 70% of water loss in pools and spas is through evaporation. Of course, you also have leaks- which probably accounts for the second reason. But, how can you tell the difference? How do you prevent swimming pool evaporation?

Are you losing water because of everyday science or are you losing water because you have a leak somewhere? Honestly, both answers warrant an explanation, don’t you think? Let’s dig a little deeper. 

Losing Water Through Evaporation

Everyone knows that evaporation is just the process of liquid forming into vapor. But, how does that fit in with our swimming pool? Evaporation occurs whenever you expose wind or air to the surface of your pool. So in short, this applies to every pool, all the time. Water molecules rise to the surface, form into a vapor and eventually get released into the air.

Heated pools on cool nights experience evaporation more rapidly. This is also why heated pools lose most of their heat overnight. Luckily for us, there are ways to fight evaporation.

Cover Your Pool and Spa

The best way to prevent evaporation is by purchasing a pool cover. According to a study by the National Pool Industry Research Center (NPIRC), pool owners can save a considerable amount in water savings by covering their outdoor swimming pools.

In fact, pool covers can reduce evaporation by 95%!  Honestly, that alone is enough proof for me to consider purchasing a pool cover. However, there are other benefits to adding a cover to your pool.

In addition to preventing pool evaporation, pool covers also keep the warmth inside your pool. I mentioned earlier that when you’re losing water via evaporation, you’re also losing a lot of the heat generated by your heater or heat pump. The cover traps the heat inside the pool and reduces the energy demand on your pool equipment. Additionally, owning a pool cover reduces the number of chemicals you’re using, reduces the debris in your pool, and reduces the amount of time you operate your pump and filter.

Keep in mind, there are several different covers you can purchase for your swimming pool. Here is some more information on the types of covers and their benefits.

The 3 Cover Types for Above Ground Pools

Safety Cover vs. Winter Cover

Turn Your Pool Water Features OFF

I love pools that have extra cool features like waterfalls and jets. However, if you want to help prevent pool evaporation, we recommend turning them off from time to time. Waterfalls and jets increase the amount of water exposed to sun and air. As a result, they are also more prone to evaporation. Laminar jets or cascading waterfalls have the greatest chances of higher evaporation.

We recommend turning your water features off, especially when they are not in use. This can save you money on water and on chemicals. Of course, when you’re ready to entertain guests again, turn those babies on again.

Lower Your Water Temperature

As we know, warmer water evaporates at a faster rate than cooler water because the molecules are moving faster. As the temperatures drop, the warm water evaporates even faster. In warm water, molecules turn into mist, which evaporates quickly. This process accelerates when the temperature of the pool water is higher than the air’s temperature.

Cold water is more resistant to evaporation. Keep this in mind if you’re trying to prevent evaporation and save money on water.

How Can You Tell If You’re Losing Water From Evaporation?

One sure way to determine whether your pool is losing water from evaporation or from a leak is to perform a water bucket test. To perform a bucket test, complete the steps below.

  1. Fill your pool to its normal level. Using a standard bucket, fill it to 1 inch from the top with pool water.
  2. Place the bucket in the pool at about five inches. You can set it on the first or second step of your pool.
  3. Mark the water level inside the bucket and the water level outside the bucket. (You can use a marker or piece of tape)
  4. Return after 24 hours to compare the inside water level on the inside to the water outside.

If the water level outside of the bucket dropped more than the water level inside of the bucket, then you likely have a pool leak. At this point, we recommend calling a professional. 

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Make sure to check the bucket at the 24-hour mark to avoid inaccurate results. If it rains, wait until it stops to perform the test. It will obviously give you inaccurate results, as well.

Remember, losing water to evaporation is normal- until it isn’t. Purchasing a swimming pool cover is the ideal method to prevent swimming pool evaporation. Not only does it prevent water from escaping your pool, it also traps any heat your heater or heat pump generates.

If you’re losing more water than you think evaporation allows for, perform a water bucket test. The bucket test is the easiest and cheapest trick homeowners have available.

author avatar
Charlie Ramirez
Writer at InyoPools.com, brings a wealth of knowledge and expertise in pool care and equipment, helping pool owners make informed decisions for over a decade.

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45 responses to “How To Prevent Swimming Pool Evaporation”

  1. Elgee Avatar

    Hi I have a pool cover on but its loosing water fast…It has holes in for water to go inside if it rains can it be that? Or do I have a leak and how do i find the leak?

    1. Matthew Simmons Avatar

      How much water do you lose in a day? Depending on how quickly the water is lost, you may be dealing with a plumbing issue instead of cover problems.

  2. Rita Hawk Avatar

    Question: I am looking for a way to reduce the amount of evaporation that occurs over the winter months. I switched from a heavy winter cover to a more lightweight one several years ago, and I’m sure that’s part of the cause. (My winter cover is so stinky I throw it away every spring and don’t want to throw away a pricey heavy weight one- the light weight is disposable in my opinion) So I’m wondering if I could add another layer of protection, such as perhaps leaving my solar cover on the pool under the winter cover since a solar cover reduces evaporation. Or perhaps I could do two light weight winter covers and every year toss the yucky one. Thoughts? (Above ground pool, 14 x 28, 10,000 gallons) Thanks in advance for you thoughts

    1. Matthew Simmons Avatar

      I’d look into one of the liquid pool cover products. These products dispense a liquid that creates a thin chemical boundary over the surface of the water that slows down evaporation.

      If the pool is closed, why are you concerned with evaporation?

      1. Rita Hawk Avatar

        Because in spring when I open it, it’s down a good 18 inches (and costs 200 + bucks to top off) It would cost more if I did it from my hose BTW.

        1. Mike Avatar

          Rita, I am not an expert but that sounds clearly like a leak to me. You surely should have no evaporation of any significance with a cover?

  3. David Avatar

    Anyone have little nicks or irregularities in your pool that tend to attract algea? I have a few where the walls meet the floors. I don’t have algea issues but will see some green in these nicks as they can’t be brushed easily. How have you repaired these? Caulk? Add concrete or plaster in the off season to smooth it out?

    1. Matthew Simmons Avatar

      Pools can form circulation dead spots, where the flow of freshly chlorinated water just kind of dies off, leaving a corner of your pool (or wherever) with stagnant water. You can try adjusting the return jet nozzle to get the water churning a little better in that area

      I would make a point to brush trouble spots more often to prevent algae from getting a foothold.

  4. Geoff Stanistreet, Melbourne Australia Avatar

    Hi ..your advice was a revelation !..For years ..more like decades ..I thought our pool was leaking . I replaced spider gaskets , multi port valve springs …provided new shut off values on the wastes.. did dye traces and bucket tests..all to no avail ..then I read your advice on the causes of evaporation …YES we do have a waterfall water feature and I turned it off .. and guess what ..THE WATER LEVEL DIDN’T GO DOWN ! ..Its been like that for over a month. I relaid this to my pool shop guy and he gave smile ..the secret is out!…thanks heaps for your advice ..Brighton Victoria Australia

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