Pool alkalinity is a measure of the acidity or basicity of a water sample. It is expressed in terms of the pH scale, with 7 being neutral, lower numbers being more acidic, and higher numbers being more alkaline. Alkalinity affects the stability of pH by resisting changes in that direction. High alkalinity means that it will take a lot to change the pH level, while low alkalinity means that small fluctuations in pH can occur easily.

Ideally, the TA level in your pool should be 100-150 ppm (parts per million). This will allow for a stable pH level which allows your chlorine to do its job of sanitizing the water.

If your pool’s alkalinity level is too high, it can be difficult to lower the pH level. This is because high alkalinity resists changes in pH direction. This can hit you right in the pocketbook by making your chlorine less effective and causing you to use more chemicals. High alkalinity can also cause calcium buildup which can create scaling in your pool.

Low alkalinity can cause your pH level to fluctuate easily, which can be harmful to your swimming pool water and will make for an uncomfortable swimming experience, irritating swimmers’ eyes and also doing damage and reducing the life of swimwear. Additionally, low alkalinity can also cause corrosion and staining on your pool’s surfaces.

There can be a number of causes for fluctuations in total alkalinity in pools. Some of the most common are:

• pH imbalance: When the pH level is not stable, it can cause the alkalinity to fluctuate as well.
• Improper stabilizer (cyanuric acid) levels: If the stabilizer level is too high or too low, it can also affect the alkalinity.
• Hard water: If your pool has hard water, it will contain more minerals which can also affect the alkalinity.
• Heavy usage: If your pool gets used a lot and you have low chlorine levels it’s also fairly common to see this raise your pH and alkalinity levels.
• Chlorine-based pool shock: This can be very alkaline and using it regularly can throw your levels out of balance.

If your pool’s alkalinity level is too low, you can raise it by adding baking soda to the water. This will add alkalinity and also help to stabilize the pH level. Add 1.5 pounds of baking soda for every 10,000 gallons of water in your pool. Be sure to test the pH level after adding the baking soda and adjust as necessary.

If your pool’s alkalinity level is too high, you can lower it by adding muriatic acid to the water. Add 1 gallon of muriatic acid for every 10,000 gallons of water in your pool. Be sure to test the pH level after adding the muriatic acid and adjust as necessary to get yourself to a range of 100 to 150 ppm.

It gets a bit trickier if you want to lower alkalinity but not lower the pH, as usually adjusting one will impact the other in the same direction. However, one way to make this happen is to aerate your pool after adding acid. If your pool has a fountain or water feature, that should do the trick. If this is a regular problem, you may have to install a dedicated aerator.

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