Also Known As: Muriatic acid
Because of its corrosive qualities, hydrochloric acid is useful in removing algae from pool walls and floors. Adding hydrochloric acid to pool water can also help bring down elevated pH levels. But it can burn the skin and eyes, so the chemical should be handled with extreme caution.
To bring down pH levels, add hydrochloric acid to a plastic bucket of pool water. Follow the manufacturers instructions for the correct ratio of acid to water. Allow the diluted acid to sit for at least 30 minutes. Then, with the pool filter running, add small amounts of this solution directly into the pool water, completely around the perimeter of the pool. Be careful not to dump large amounts of the acid to the pool water at one time. Allow the filter to run for about four hours and then retest the waters pH.
Hydrochloric acid should not be added while swimmers are in the water. To insure that the acid has dispersed completely, its a good idea to balance pH levels early in the morning.