Which chemical is commonly used to lower pH levels in pool water?

Hydrochloric acid is widely recognized as a chemical effectively used to lower pH levels in pool water. When pH levels rise above the desired range, which is typically between 7.2 and 7.8, adding hydrochloric acid helps to decrease the pH by introducing additional hydrogen ions into the water, effectively balancing the acidity. This adjustment is crucial for maintaining water clarity, equipment longevity, and preventing skin or eye irritation for swimmers.

On the other hand, chlorine serves primarily as a disinfectant to kill bacteria and sanitize the pool, rather than to adjust pH levels. Calcium carbonate is often used to increase alkalinity and pH levels, which makes it unsuitable for lowering pH. Sodium bicarbonate, similarly, is mainly utilized to raise the alkalinity and can also have a mild effect on increasing pH rather than reducing it. Thus, hydrochloric acid is the appropriate choice for the objective of lowering pH levels effectively in pool water.