Ensure your pool dazzles next season by acting now to remedy and prevent scale deposits.

To help our readers better understand what causes scale, and how to prevent it, we’ve answered the following common scale questions.

Q: What does scale look like?

A: Scale can take the form of white, gray or brownish chalky deposits on your pool walls and fixtures. Scale is typically composed of calcium carbonate and is most likely to form in a pool’s heater. Buildups can also occur on pool walls along the waterline. These deposits are usually a combination of precipitated calcium carbonate and whatever other substances you have floating on the surface of your pool water.

Q: What causes scale?

A: Scale can be caused by high pH, total alkalinity and calcium hardness levels for a significant period of time. Having high levels of all three factors allows the calcium carbonate to separate, or precipitate out, to the point that it becomes visible, making your water appear cloudy. Eventually this calcium carbonate will stick to your pool walls or equipment, forming a tightly bonded residue known as scale.

maintaining a clean pool

Q: Are certain geographical areas more prone to scale deposits?

A: Scale can be a problem anywhere, but especially in areas that have high water hardness and high evaporation, like the Southwestern region of the United States. Areas with limestone deposits in the ground water also tend to exacerbate the calcium hardness levels, resulting in more problems.

Q: Why is scale a problem?

A: Scale crystals can be sharp and abrasive on skin, especially for young children. Scale buildup is unattractive on pool walls and railings because it imparts a dingy gray or tan color to the pool’s surface. Significant scale buildup in your heater can also reduce the flow of water and heat transfer from your pool, rendering the heater less efficient. If the buildup is allowed to get bad enough, you might need to replace the heater entirely.

Q: What can I do to prevent scale buildups?

A: Keep your water balanced. This means adjusting your pH, total alkalinity and calcium hardness levels so they are within the proper ranges. Properly balanced water helps keep calcium carbonate saturated to the correct levels. This means the calcium is dissolved in the water and isn’t visible.

One of the keys to avoiding scale buildup is following your normal maintenance schedule, as scale often results from lack of attention. Scale buildup is not something that develops overnight. Part of that maintenance schedule is regularly bringing a pool water sample to your authorized dealer to guard against scale buildup and correct your water balance before scale becomes a problem.

Q: What should I do if I notice scale deposits on my pool?

A: First you should test your pool water and correct your water balance, which is causing the problem. Waterline scale can sometimes be removed by scrubbing with a brush or sponge and using a tile cleaner for chlorine-free pools or for chlorinated pools. Serious scale buildups such as that you might find in your heater can be impervious to scrubbing. Scale sticks because it chemically bonds to pool and equipment surfaces. You will need to consult with your dealer on the best way to remove the scale deposits from your pool.


Whether you’ve noticed the first signs of deposits or want to take preventative measures, it’s easy to keep scale problems in check. Maintaining a clean, scale-free pool is one of the best ways to ensure lasting beauty and enjoyment.

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