Which substance can be added to the swimming pool to lower the pH?

Adding muriatic acid to a swimming pool is an effective method to lower the pH level. Muriatic acid, which is a diluted form of hydrochloric acid, helps correct alkaline water conditions, making it highly useful for pool maintenance. By lowering the pH, muriatic acid can help prevent issues such as scale buildup, cloudy water, and skin irritation for swimmers.

Other substances mentioned have different purposes. For instance, sodium chloride is primarily used for saltwater pools for sanitation rather than adjusting pH. Hypochlorite acid can act as a chlorine source and may impact pH, but not specifically for lowering it effectively. Soda ash, on the other hand, raises pH levels and is used when water is too acidic, which contradicts the goal of lowering pH. Thus, muriatic acid stands out as the appropriate choice for pH reduction in swimming pools.