How to Cool the Pool


Swimming pool water a little warm? If your pool gets lots of sun, summertime water temps can reach the high 80's or even 90°. Too warm for a refreshing swim, it's like bath water!

Heat consumes chlorine, and makes it easier for algae to grow, who prefer the warm water. What to do when your swimming pool feels  like a hot tub?

I took a short walk from the In The Swim Offices to the R&D building, to speak with the one guy who could help me with this question.

"Hi, Dr. Pool, can I ask you a few questions?" I asked. "Certainly David" he said, peering over his safety glasses. "What can I do for you?"


Everyone has this idea pop into their head first, but can you really lower pool water temperature with ice? "Of course you can, but you would need a truckload of ice, thousands of pounds, to lower the temperature even 5 degrees", he said.

I pressed him for a formula for determining how much ice would be needed to lower pool water temperature, so he scratched this out on a slip of paper.


Where PV = Pool Volume (in gallons) and TR = desired Temperature Rise. For example, cooling my 25000 gallon pool down 10 degrees Fahrenheit would look like this: 25000 ÷ 1000 x 10 x 4.375 = 1094 lbs of ice! That's gonna be pricey!


I asked Dr. Pool about this one too, and the look on his face told me that this is another idea that's going nowhere. Great for adding a spooky fog on the surface of the pool, but not so good for lowering pool water temperature. "Dry Ice evaporates into a gas as it cools, not into water - having very little effect on pool water temperature", he said. He also warned that it will pummel your pH level, being very acidic, and could cause skin burns if swimmers touch it. Ok - next idea!


three tiered pool fountain, item A5500

"Aeration can reduce pool water temps, especially in arid regions, but if the outside air is warm and humid, the effect will be minimal". He explained that aeration of the water (spraying it over the surface) cools the water by evaporation during the few seconds that the water droplets are airborne. "Pool fountains or cascading water features can be used to lower water temperature 5 or 10 degrees, depending on humidity levels and volume and type of spraying apparatus used". "Like our Triple Tier pool fountain!" I said, he nodded.


I know that this one works; when I lived in Texas, I used our solar pool heater at night, to cool water temperatures. But I ask him anyway, as a sneaky little test. He paused for a moment and said "Are you talking about solar pool heaters? I suppose you could, if you shut it off during the day, and ran the system during the night, there should be a reverse radiant effect." Good answer, Doctor. I told him that in arid regions with hot days and cool nights, running the solar system for a few hours in the early morning hours keeps lots of pools from overheating during August. "Yes, exactly David. I suppose it would depend upon the size of your solar system, the humidity and the night time air temperature, but it certainly seems like a viable method - if you have a solar pool heater".



The good Doctor gives me a knowing nod, realizing the game I'm playing. "Now you must be hinting at pool heat pumps, no?" I shrugged and nodded to the affirmative. "As you know David, some heat pumps have the ability to reverse the flow of the refrigerant, and behave as an air conditioner. What are those called?" "Chillers", I replied. That's the term used for pool heat pumps that have a "chilling effect" just as Dr. Pool described. They normally run as a pool heater, but at the flip of a switch, can operate backwards and pull heat out of the pool water and discharge it into the surrounding air. "Chillers are quite expensive, are they not?" he asks me. He is correct, the Heat/Cool heat pumps for pools start at $3999, but could be the easiest way of reliably cooling a hot pool.


  • Add Shade over the pool. Shade sails or cabanas to block the sun.
  • Add Water to the pool. 2 inches of water can lower temp by 1-2°.
  • Run the pump at night, aim jets to surface to increase circulation.
  • Open the main drain or run pool cleaner, to equalize thermal layers.
  • Set-up large fans to blow across the water during the evening/night.
  • Use the Pool! Cannonballs and splash fights disperse water heat!

Thanks, Dr. Pool! I'm glad we got to the bottom of this question about how to lower the water temperature in a swimming pool.

In The Swim makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and In The Swim assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. In The Swim assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.