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What Causes High Alkalinity in Swimming Pools?

The maintenance of alkalinity levels is an important aspect of keeping your water chemistry in balance. Only a few factors can actually lead to high amounts of alkalinity, some of which are beyond your control. What is your responsibility, however, is to lower the alkalinity levels as soon as they elevate to avoid other pool water-related problems.


The measurement of alkalinity is used to determine how resistant the pool water is to neutralize acid. To maintain sanitized and properly balanced pool water, testing kits for swimming pools indicate that a normal alkalinity reading should fall somewhere between 80 and 120 parts per million (ppm). Too much alkalinity will adversely affect pool chemistry and pH readings. The alkalinity serves as a buffer to the pH, which means when alkalinity is balanced, the pH is more likely to stay in the neutral range as well.


In many cases, when first filling up a pool or opening it for the spring season, the alkalinity levels may need to be raised. Pool owners who overestimate how much alkalinity-increasing chemical they need can sometimes push the alkalinity to levels above 120 ppm. This reason and another completely out of your control is the alkalinity readings in your particular water supply. In some areas alkalinity is higher than others. Therefore, when filling up your pool for the first time, the alkalinity levels may need to be lowered.


High alkalinity needs to be lowered immediately to avoid other pool chemistry-related problems which will take more time, energy and money to remedy. High alkalinity can lead to cloudy water, itchy skin and scalp, water circulation problems with your filter, reduced chlorine effectiveness and a difficulty receiving an accurate and stabilized pH reading. The pH is difficult to stabilize because the buffer that regulates the pH is not in balance either. Although alkalinity and pH are too separate entities, they are dependent on one another.


High alkalinity is easily solved by adding sodium bisulfate to your swimming pool, which is often marketed as pH and alkalinity increaser or pH-up. The chemical to lower both alkalinity and pH is one and the same. To accurately lower the alkalinity to the right levels, you must test the water. Determine how much you need to lower the alkalinity and how many gallons of water you need to treat. Consult the product guidelines prior to adding the chemicals to the water.

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