Pool Cooling: How to Cool Down The Pool Water and Keep It Cool?

Summers are getting hotter, and having your own pool is the best way to cool off. But what if the pool water is too warm and has to be cooled beforehand?

In summer, the pool water can best be cooled with an overnight filter system or solar collectors. Alternatively, a reversible heat pump that creates a cooling circuit is suitable. Good ways to keep the pool cool are fountains and sails.

In this article, you will find the best tips on how to keep a pool cool. I also get to the bottom of the cause of the pool water being too warm.

Use the filter system to cool the pool water overnight

The easiest way to cool a pool is to let the filter system run overnight.

In the evening, the temperatures drop, and some of it evaporates due to pool water circulation. As a result, the water temperature drops, and the pool is a little cooler in the morning.

A timer is helpful, so don’t forget to start the pump in the evening.

Don’t expect too much from this method, however.

The water temperature in the pool will drop by a running filter pump in the evening – in the best case – only by 2 to 5 degrees Celsius.

On sweltering summer days in June and July, even the evening hours can be pretty warm, and the effectiveness of this method is significantly reduced.

Before you let the filter system run overnight, you should inquire about the legal situation in your residential area.

It is not always allowed to let the pool filter run overnight.

To not negatively influence the relationship with your neighbors, I recommend building a soundproof hood around the sand filter. This can significantly reduce the noise level.

A pool pump in continuous operation will drive up electricity costs. Therefore, you should use other methods to cool the water in your swimming pool.

Use the solar heater against warm pool water

With a solar heater, you can heat your pool and cool it.

I’m talking about an absorber system for swimming pools.

The absorbers are made of black plastic and absorb the heat from the sun. The water in the pool flows through the absorber, absorbs the heat, and then flows back into the pool at a higher temperature – the pool is heated.

When the air temperature has dropped in the evening, you let the pool water flow through the absorber to lower the water temperature.

Due to the large area of ​​the absorber, the heat from the water is simply given off to the ambient temperature.

This means: The larger the surface of the absorber, the faster your pool is cooled. In addition, larger areas of solar heating are more practical when heating your swimming pool.

Large absorbers are always better if you decide to buy a solar heater.

The use of solar heaters saves water treatment costs and protects the environment.

If we assume a realistic efficiency of 30% for the solar collectors, you can cool a pool by 3 to 5 degrees.

However, you need space in your garden to install a solar absorber. An alternative would be a solar collector in the form of a dome.

But don’t buy solar panels that are too small if you don’t have enough space in your garden!

Absorbers of 100×100 cm and below are too small for large pools.

I am a supporter of this technology, and I am eagerly following the further development in solar cooling that is being pushed forward in Japan.

Tip: If you want to heat your pool with a solar collector, you need a south-facing orientation. An installation on your house roof is suitable here.

Cool the pool with a reversible heat pump

The reversible heat pump can heat a pool, but it also has a cooling circuit that can be used to lower the water temperatures in your pool.

The principle: Ambient heat is necessary for the heat pump to work. With electrical energy, force inside the pump is generated, which increases the temperature. The heat is then transferred to the swimming pool water in the condenser.

But we don’t want to heat our pool water. We want to cool it down.

Then why should I buy a heat pump?

A reversible heat pump can automatically reverse the heat cycle and cool your pool.

The heat pump is expensive to purchase but works 70% with the energy of the ambient temperature and only 30% from electricity.

If you decide to buy a heat pump, then buy a correspondingly powerful heat pump. A small heat pump leads to long heating times and cooling processes.

A solid heat pump starts at around 8 kWh.

Modern heat pumps can also passively cool the pool using a heat exchanger.

The heat from the pool water is passed through a heat exchanger in which the heat is given off. This process reduces the already low electricity costs for operating a heat pump.

Install a fountain in the swimming pool

The fountain in the pool is a simple and inexpensive method to cool the pool in the long term.

It is well known that running water is colder than standing water.

With the help of a fountain, the water cools down more quickly due to the trickling in the air.

You have the choice between a classic pool sprayer or a solar fountain. I don’t recommend solar technology in this case, as the functionality does not work overnight.

Partial water change in the pool

The complete water change in your pool should only take place once a year in order to save water and costs.

However, some water has to be changed if the proportion of cyanuric acid in the pool is high.

Actually, I didn’t want to list this possibility to cool a pool. Still, it happens pretty often that inexperienced pool owners pursue it.

Theoretically, you can change a part of the pool water and therefore cool the pool.

The supply of fresh water will lower the temperature in your swimming pool. However, the pleasant water temperature does not last long.

In sunlight, the temperature in your pool rises again to an uncomfortable level. As a result, the procedure has to be repeated over several days – this is pure water waste.

Far worse, however, are the pending costs for the pool chemistry.

Each time the water is changed, the parameters ​​must be balanced. If this does not happen, algae will grow, which color the pool water green.

Changing the water is an option in a small paddling pool or in a whirlpool. The costs remain within reasonable limits, but changing the water is not practical for large swimming pools.

Cool the pool with ice

While looking for other methods of how to cool a pool, I came across the suggestion to cool the pool water with ice – NO DRY ICE.

That might sound strange, but if you have access to large amounts of ice, you can use it to cool your pool to a comfortable water temperature.

The only problem with ice in your pool is that you need quite a bit of it.

To cool a pool with 35 m³ of pool water by 5 degrees, you need about 991 kg of ice.

That’s a lot!

Such large amounts of ice will inevitably raise the water level in your pool.

Furthermore, the water balance is changed drastically. Here you should check the parameters with a water tester after using ice in your pool and, if necessary, improve them with chemicals.

But be careful: Under no circumstances should you cool a pool with dry ice.

Dry ice is a form of carbon dioxide, and you can choke on it. Unfortunately, it has already happened that people tried to cool the pool water with dry ice and died in the process.

Once again: Stay away from dry ice!

Sun protection sails over the pool

Too much direct sunlight is dangerous for humans. It can also cause the water temperature in your pool to rise.

To prevent this, large sun protection sails in your garden are suitable.

The sun protection sail provides shade for your pool and keeps the temperatures constant.

You will not directly cool the pool with a sun protection sail. You only prevent the water from getting too warm with the created shadow.

But unfortunately, shade sails are usually not long enough to cover a large pool over 7m in length.

In addition, the ropes must be stretched accordingly – an alternative would be a pavilion over your pool.

However, a pool roof is recommended for a small Intex above-ground pool and gardens with space.

But you have to be careful that the roof does not build up too much heat around your pool. You can find out how to prevent this in the chapter on wind blockers.

Remove wind blockers near the pool

Removing the wind blockers near the pool is also one of the ways you can prevent the pool from overheating.

Are there a lot of trees and hedges around your pool?

These lead to the fact that the wind is blocked, and the heat in your pool continues to rise.

Hedges, bushes, and glass walls are ideal if you want to heat your pool, but not if you’re going to keep your pool cool in summer.

You should support the wind to keep the water temperature within a comfortable range.

Paradoxically, you want to keep the pool warm on cold days. Just too stupid that the hedge does not grow back overnight.

In this case, I recommend simple privacy protection mats, which you can put up and take off again.

The wind helps to keep your pool cool and also encourages the water to circulate. So it makes sense to remove the wind blockers around your pool if necessary.

Questions and answers about the temperature of the pool water

I have listed the most common methods to cool down your pool.

Easy implementation and the cost factor were important to me when I wrote the article.

However, there are still a few questions to be clarified regarding the water temperature.

If you have unanswered questions, you may find them here.

What are the reasons the pool gets too warm?

Your pool gets warm in summer, which is a problem that many pool owners struggle with.

Most of the time, the heat in your pool increases due to one of the following reasons:

  • Rising temperatures in the pool due to wind blockers such as hedges and trees.
  • Trapped air under the pool cover.
  • Too long heating times above the comfort temperature.

If you want to control your pool from getting too warm in the summer, make sure the wind can work in your favor.

If possible, remove the pool cover overnight and avoid running the heat pump too long.

How warm should the pool water be?

Bacteria and algae feel most comfortable in a warm pool.

From a water temperature of 78 °F, algae can always be expected in the pool – if the water parameters ​​are incorrect.

I recommend keeping the pool water constant at 70 °F (22 °C).

Humans feel most comfortable in the water at a temperature of 77 – 83 °F (25 to 28 °C). For seniors, the water temperature should be 96-88 °F (30 to 31 ° C).

Use a break-proof thermometer that floats in the water.

Every pool owner has to decide for himself how warm the pool water can be. You can find more information on this topic in my blog.

Can you swim in pool water at 60 °F?

I don’t see any obstacles to why you should not swim in 60 °F cold pool water.

Cooling down is very important, especially in midsummer. Source.

Bathing in cold water is considered healing in many countries, including Sweden and Russia.

People like Wim Hof ​​have set a trend in which people spend a lot of money to do a workout in cold water.

Take the chance for a cold swim in your pool, but make sure that your body acclimates to the temperatures before jumping into the cold water.

How do you calculate the cooling in the pool?

Water is much easier to heat than to cool – laws of physics.

Still, you may be wondering how long you need to cool a pool to make bathing more fun.

In my experience, with the proven methods to cool a swimming pool, it takes one day to cool down your pool at a comfortable temperature.

Newton has developed a formula for this: Newton’s law of cooling.

∆T / ∆t = -k (T-Tu)

∆T = T (t + ∆t)

  • T (t) Tu: Ambient temperature
  • T (t): Temperature
  • k: Cooling factor

The formula should function as a small distraction while waiting, or you can use the time to clean the pool floor.

By the time you calculate the cooldown time, your swimming pool has already cooled, and the question of how long it will take to cool down your pool is superfluous.

Do you have further questions about pool cooling?

Contact me on Twitter at @contactswimfool. I am happy to help you.

Have fun cooling your swimming pool!

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Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

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