Pool Alkalinity: Everything You Need to Know

Pool Alkalinity 101

Is your pool water cloudy? Or do you get irritated eyes when you go for a swim? Then, your alkalinity levels may be off. One of the best-kept secrets to perfect pool water is simply understanding and maintaining the correct alkalinity levels.

In this article, we’ll cover everything you need to know about pool alkalinity, from what it is and why it is vital to the best ways to measure and adjust it.

What is Alkalinity in a Pool?

Alkalinity is part of the composition of water, and it measures the water’s ability to neutralize acids. It also measures the buffering capacity of water to resist changes to pH. By keeping the right alkalinity level in your pool, you balance the pH level in the water.

pH vs. Alkalinity

The pH scale measures a substance’s acidic or basic levels on a numbering gauge between 0 and 14. This is based on how much hydrogen is in the substance, which can cause the substance to be more acidic or basic. 0 is the most acidic with items like battery acid and lemon juice. Seven is neutral, and pure water sits here. 14 is the most basic, with items like baking soda and bleach. The pH level of a pool should be between 7.2 and 7.8 to keep your pool clean and healthy.

Alkalinity, on the other hand, is a measure of the water’s ability to resist changes in pH. The ideal range for alkalinity in a swimming pool is between 80 and 120 ppm (parts per million). When the alkalinity is too low, the pH level can change rapidly and become unstable. When the alkalinity is too high, it can be challenging to adjust the pH level.

pH and alkalinity are closely related and interact with other pool chemicals, such as chlorine and calcium hardness. Chlorine, for example, is more effective at killing bacteria and algae when the pH is between 7.2 and 7.8. If the pH is too high or too low, chlorine can become less effective.

Measuring Alkalinity

Methods for measuring alkalinity in a swimming pool

  1. Test strips are an easy and convenient way to measure alkalinity. To use a test strip, you dip the strip into the pool water and compare the color to a chart on the package to determine the alkalinity level.
  2. Liquid test kits are similar to test strips, but they use a dropper to add a liquid reagent to a pool water sample. The color change of the water will indicate the alkalinity level on the chart on the package.
  3. Electronic testers use a sensor to measure the alkalinity level. They are more accurate than test strips or liquid test kits but are also more expensive. For electronic testers, follow the manufacturer’s instructions for how to use the device.

Low Alkalinity

What causes low alkalinity?

Various factors, including heavy rain, high evaporation, and backwashing of the filter, can cause low alkalinity.

What happens if pool alkalinity is too low?

The pH level can become unstable and change rapidly if the alkalinity is too low. This can lead to various problems, including cloudy water, irritated eyes, and damage to pool equipment.

Low alkalinity can also cause chlorine to become less effective at killing bacteria and algae, turning your pool water green. Always test and adjust as you go through these processes.

How to raise alkalinity in a pool

To raise alkalinity in a pool, you can use these methods:

  1. Add baking soda (or sodium bicarbonate). Start by adding a small amount of baking soda and then retest the alkalinity levels. If necessary, add more baking soda until the alkalinity level is within the ideal range.
  2. Use a commercial pool alkalinity increaser. These products contain sodium carbonate and are specifically designed to raise alkalinity levels. One of my favorite products to use is produced and sold by Clorox.
  3. Add sodium hydroxide (lye) to the water. This is a strong chemical and should only be used by professionals or those with experience handling it.

High Alkalinity

What causes high alkalinity?

High alkalinity can be caused by adding too much baking soda to the pool or not backwashing the filter often enough.

What happens if pool alkalinity is too high?

If the alkalinity is too high, it can be difficult to adjust the pH level. It can also lead to scaling on pool surfaces and equipment, cloudy water, and eye irritation.

How to lower alkalinity in a pool

Here are a few ways to lower the alkalinity in a pool:

  • Use muriatic acid (hydrochloric acid) to lower the pH and alkalinity levels. The amount needed will depend on the size of the pool and the current alkalinity level.
  • Use a pool pH decrease product. These products contain phosphoric or sulfuric acid and are specifically designed to lower pH and alkalinity levels.
  • Add sodium bisulfate (dry acid) to the water. This granular acid can be used to lower the pH and total alkalinity.

It’s important to note that before adding any chemicals to your pool, you should test the water’s current alkalinity level and pH level. You should also read and follow the instructions for any chemical product you use and be aware of the safety precautions.

It’s also essential to make minor adjustments over time rather than trying to lower the alkalinity level all at once. Making large adjustments at once can disrupt the water’s chemical balance and cause other issues.


Maintaining the right alkalinity level in your pool is crucial for keeping the water clear, clean, and safe for swimming.

By understanding pool alkalinity, how to measure it, and how to adjust it, you can ensure that your pool is always in top condition and ready for fun. Happy swimming!

About the Author

stefan schulzStefan Schulz is the founder and owner of PV Pool Cleaner. He spent his college years working at Niagara Pools and Spas, one of the largest Swimming Pool and Hot Tub Dealers in the Eastern United States.

Today, he utilizes his background, experience as a pool owner, and the resources of his digital marketing agency, Orpical Group, to generate informative and engaging content for pool owners everywhere.