Transchem 26499047531 1 gal 31.45% Muriatic Acid - Muriatic Acid is a pool chemical that can be used to maintain pH balance and lower alkalinity in pool water. Muriatic Acid can also be used as a cleaning agent on pool surfaces and tiles. At the end of the pool season, use Muriatic Acid to clear out any mold or algae leftover in your pool.