What Causes High pH and Alkalinity in Pool Water?

Pool water chemistry is a crucial aspect of pool maintenance, and pH and alkalinity are two vital parameters that require regular monitoring. The pH level in pool water refers to its acidity or basicity, while alkalinity is a measure of the water’s ability to resist pH changes. 

It is essential to know what causes low pH in swimming pools, how to raise the pH in your pool when it drops, and how to lower the pH when it’s too high. In this article, we will take a closer look at what might cause high pH and alkalinity levels in a swimming pool, and how to adjust these levels.

What Are pH and Alkalinity?


Your pH level measures the concentration of hydrogen ions in water and indicates whether the water is acidic or alkaline on a scale of zero to fourteen. A pH level of 7.0 is neutral, below 7.0 acidic, and above 7.0 is alkaline. The ideal pH level for swimming pool water is between 7.2 and 7.8.


Alkalinity describes water’s ability to neutralize acids and resist changes in pH. Total Alkalinity (TA) is typically measured in parts per million (PPM), and the ideal range is between eighty and 120 PPM. Maintaining appropriate pool water alkalinity helps prevent rapid pH fluctuations and prolongs the longevity of pool equipment.

What Causes High pH and Alkalinity in a Pool?

Poor Hygiene

Pool users can introduce various organic contaminants, such as sweat, urine, and body oils, to pools, altering the water’s pH levels. High uric acid levels can lead to alkaline pool water.

Shock Treatments

Using shock treatments to sanitize the pool can cause temporary increases in pH and alkalinity levels. Shock treatments should be carried out at measured intervals to avoid prolonged effects on a pool’s pH and alkalinity. 

Should you shock your pool or adjust pH first? Your pH levels should always be correct before you proceed to shocking your pool.

Hard Water

Water hardness is a result of dissolved minerals such as calcium and magnesium. This mineral buildup can lead to an increase in alkalinity and pH levels.

How Can You Decrease High pH and Alkalinity in Pool Water?

Acid Addition

Adding acid is a common way to decrease pH and alkalinity levels in swimming pool water. Muriatic acid is commonly used for this task. The addition of an acid to pool water lowers the pH level and reduces alkalinity. However, it’s essential to add the acid in small doses, while checking pH levels at regular intervals to avoid excessively lowering the pH.


Aeration increases oxygen levels in the water, causing the carbon dioxide to escape and alkalinity levels to drop. Aeration devices such as fountains, waterfalls, and air blowers are common ways of aerating pool water. Installing pool covers also helps rainwater from entering and disrupting the pool chemistry.

Alkalinity Reducers

Alkalinity reducers are chemicals that help lower pool water’s pH and alkalinity levels. Sodium bisulfate and sodium bisulfite are commonly used alkalinity reducers. These additives work by breaking down the alkalinity in the pool water.

Drain and Refill

Draining and refilling the pool can be used to decrease high pH and alkalinity levels in swimming pool water. If you’ve tried other methods with little success, completely draining and refilling your pool can be a last resort.

In Summary

Having the right pH and alkalinity levels is essential when it comes to both the beauty and safety of your pool. Learn what factors cause these elements of your pool chemistry to increase, and you can use preventative measures and act accordingly when they reach undesirably high levels.

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