Expert Verified Updated: March 2026

Pool Cooling Time Calculator - Evaporative Cooling Guide

Calculate how long it takes to cool down a hot pool using aerators, fountains, or overnight exposure. Use evaporative cooling to drop water temperature.

Evaporative Cooling 101

The fastest way to cool a pool is through evaporation. When you spray water into the air with a fountain, or pointing your return jets up to "bubble" the surface, you are increasing the surface area for evaporation. This releases massive amounts of latent heat, dropping the water temperature quickly.

Pro Tip: Only cool your pool at night. Cooling during the day is often cancelled out by solar gain from the sun. Turn on your fountains at sunset and off at sunrise.

Actionable Steps

Factors that Stop Cooling

High humidity is the enemy of cooling. If the air is already saturated with water, your pool cannot evaporate efficiently. On a "muggy" night with 90%+ humidity, you will see very little temperature drop, even with your fountains running full blast.

Want to see the exact loss? Check the Evaporation Rate Calculator.

Pro-Tip

Only cool your pool at night. Cooling during the day is often cancelled out by solar gain from the sun. Turn on your fountains at sunset and off at sunrise.

Frequently Asked Questions

Can I just add ice?

It is extremely inefficient. To drop a 20,000-gallon pool by just 1 degree, you would need over 1,500 pounds of ice. Aeration is free and much more effective.

Will aeration raise my pH?

Yes. Aeration drives off carbon dioxide, which causes pH to rise. You may need to add a bit of Muriatic Acid after a long cooling session.

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