The most important aspect of swimming pool chemistry is pH because it affects all other chemical balances in the water. Ideally, pH should range between 7.4 and 7.6, the range most comfortable for the eyes. As pH drops, the water becomes increasingly acidic. This can cause the sides of the pool to become rough and prone to algae infections, corrode metal equipment and fittings, cause burning in the eyes and nose, fade swimwear and increase the loss of chlorine, which means the pool isn't properly sanitized. Soda ash raises the pH of the pool, but chronically low pH may also require adjustments to the total alkalinity.
Test the pH using a pH test kit. While the pH should ideally range between 7.4 and 7.6, ranges of 7.2 to 7.8 are acceptable.
Calculate the amount of soda ash (sodium carbonate) to add to raise the pH. To raise the pH 0.3, add 1 lb. of soda ash per 10,000 gallons of water. Do not add more than 2 lbs. of soda ash per 10,000 gallons of water at any single time.
Measure the correct amount of soda ash and dissolve it in a bucket of water.
Check that the pump is running and switch it on if it is not.
Pour the dissolved solution directly into the pool water and allow enough time for the pump to circulate the water at least once.
Retest the water and make a second treatment, if necessary.
Test the total alkalinity of the water, if pH continues to drop. Total alkalinity measures the water's ability to hold a steady pH. Low total alkalinity indicates that the pH of the water will drop rapidly with the addition of pool care chemicals or other substances. High total alkalinity typically makes the pH too high and isn't likely to cause chronic drops in pH. Total alkalinity should range between 80 and 150 parts per million.
Add 1.4 lbs. of baking soda (sodium bicarbonate) per 10,000 gallons of water to raise the total alkalinity 10 additional parts per million. Allow the water to circulate through the pump once before retesting and making additional adjustments if necessary.