Why Is the Alkalinity Not Dropping in My Swimming Pool?

Alkalinity

• Alkalinity is a measure of the pool's capability to neutralize acid. The alkalinity serves as a stabilizer for the pH, which is the measure of acidity in your water. The two chemicals are different but have direct relation to one another. When the alkalinity is high, the pH has a tendency to be high as well. The pH fluctuates greatly when the alkalinity is not in proper balance. High alkalinity can lead to cloudy water, itchy skin and a decrease in chlorine effectiveness.

Testing Strips

• Testing strips are a common way to quickly test your pool water. The process is simple -- you just dip a strip into the water and remove it. The readings are available in less than 15 seconds. Match the colors of the strip marking with a reference chart to get a reading of your chemical levels. However, testing strips have expiration dates. Once a testing strip expires, it's less responsive to the chemicals in the water and will give you an incorrect reading of the water chemistry. Ensure that you use fresh testing strips when checking the alkalinity in your pool water.

Sodium Bisulfate

• Treat high alkalinity with a dosage of sodium bisulfate. Pool supply retailers sell this product under the label of pH down or pH decreaser. This chemical lowers both the pH and alkalinity of your pool and appears as a fine white powder. To lower the alkalinity, disperse the pH decrease chemical along the surface of the water. Because the powder is so fine, you must get as low as possible when you disperse it so it doesn't blow away. Be very careful to not fall into the pool as you disperse it.

Adding the Chemical

• Add the correct amount of sodium bisulfate as per the manufacturer's guidelines. The amount you add to the pool will depend on your pool gallon capacity and current alkalinity levels. After you add the sodium bisulfate, you must run the filter for eight hours. Do not test the alkalinity in the water until eight hours have passed and the chemicals have circulated through the pool. If you test earlier, it will lead to an incorrect reading. If the alkalinity hasn't dropped after eight hours, it's likely that you didn't add enough sodium bisulfate to the pool. Consult the product guidelines and add the correct dosage to meet your pool's needs. The alkalinity for pools should be somewhere between 80 parts per million (ppm) and 120 ppm.