Sodium Bisulfate is also known as Dry Acid. It is produced as a clear/white, dry granular form by mixing sulfuric acid and sodium hydroxide together.
For swimming pools, dry acid is used to lower pH and decrease total alkalinity. In pools with high pH or total alkalinity, adding dry acid helps to maintain the water balance of a swimming pool. Although liquid muriatic acid is another chemical that performs similarly, dry acid is more user-friendly, is less caustic and does not damage surfaces as easily if spilled or splashed accidentally.
Dry acid is added directly to a well-circulating swimming pool water, and will readily dissolve.