The Science Behind Pool Closing

As the summer season comes to an end, it's time to start thinking about closing your pool. But have you ever wondered about the science behind pool closing? In this blog post, we will explore the reasons why pool closing is necessary and the scientific principles that make it effective.

Why is pool closing necessary?

Pool closing is an essential step in pool maintenance, especially in regions with cold winters. When the temperature drops, water freezes and expands, which can cause significant damage to your pool's plumbing and equipment. By closing your pool properly, you can prevent costly repairs and ensure that your pool is ready for the next swimming season.

What happens during pool closing?

During pool closing, several important steps are taken to protect your pool from winter damage. The first step is to balance the water chemistry. This involves adjusting the pH, alkalinity, and calcium hardness levels to their recommended ranges. Balanced water chemistry helps prevent corrosion, scaling, and staining during the winter months.

Next, the pool water is treated with a winterizing chemical. This chemical helps to inhibit the growth of algae and bacteria while the pool is closed. It also helps to prevent staining and scaling caused by minerals in the water.

Once the water is properly treated, the pool's plumbing and equipment need to be prepared for winter. This involves draining the water from the pipes, filters, pumps, and heaters to prevent freezing and damage. Any remaining water is blown out using compressed air to ensure that no water is left in the system.

How does pool closing work?

The science behind pool closing lies in the principles of thermodynamics. When water freezes, it expands and can exert tremendous pressure on the pool's plumbing and equipment. By removing the water from the system, pool owners can prevent this expansion and the subsequent damage.

Additionally, the winterizing chemical used during pool closing helps to inhibit the growth of algae and bacteria. This is achieved by altering the chemical balance of the water, making it less hospitable for these microorganisms to thrive.

By following the proper pool closing procedures, pool owners can ensure that their pool remains in good condition throughout the winter months. This not only protects their investment but also makes the pool opening process much easier when the warmer weather returns.


Pool closing is a crucial step in pool maintenance, and understanding the science behind it can help pool owners make informed decisions. By balancing the water chemistry, treating the water with a winterizing chemical, and preparing the plumbing and equipment for winter, pool owners can protect their pool from damage and ensure its longevity. So, as the summer season comes to an end, don't forget to close your pool properly and enjoy a worry-free winter!

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