Swimming pools must contain a fine balance of elements to function properly. Without this balance, the pool water may harm people swimming inside it or damage the structure of the pool. High alkalinity reduces the germ-fighting effectiveness of chlorine and irritates human skin. Two measures of swimming pool alkalinity exist: total alkalinity and pH. Total alkalinity refers to the parts per million (ppm) of dissolved solid alkaline materials. High total alkalinity keeps pH high as well, but also prevents the pH from budging from a high position. Low total alkalinity can cause the pH to fluctuate rapidly. Therefore, an alkaline pH can exist with low total alkalinity. Total alkalinity and pH adjustment methods differ, so begin with total alkalinity adjustment.
High Total Alkalinity
Measure the swimming pool's total alkalinity. Healthy total alkalinity levels fall between 80 and 120 ppm.
Calculate the amount of hydrochloric or muriatic acid needed to lower total alkalinity to healthy levels using a total alkalinity adjustment chart, or add one quart of acid for each 10,000 gallons of water.
Turn off the pool filter and put on rubber gloves and protective eye goggles. Pour the acid into the deepest part of the pool in one concentrated area.
Brush the bottom of the pool in the area in which you poured the acid after 20 minutes to prevent pool bottom etching. Do not stir the acid around the pool.
Wait three days and retest the total alkalinity. If the total alkalinity remains high, add more acid. If the total alkalinity is within healthy levels, turn the pool pump back on. Wait one day prior to testing pH.
Test the pH levels of the pool using a pH test kit. Lowering the total alkalinity also lowers pH levels. If your total alkalinity tested normal, you can lower pH without lowering total alkalinity.
Fill a bucket 3/4 full with pool water. Put on gloves and safety goggles. Pour 1/4 cup of acid into the bucket and stir. Pour the bucket of diluted acid all around the deep end of the pool.
Leave the pool filter on and wait at least four hours.
Test the pH levels again and add more acid until the pH reads between 7 and 7.6.