Primarily used to lower the pH of swimming pool water. Other uses include etching and cleaning of brick, stone, tile, concrete and other masonry surfaces. For cleaning and etching applications always start with diluted acid and test the affects in an out-of-the-way area. Always add the acid to the water when diluting. Pouring water into acid can cause splattering and violent eruption on the mixture. Acid solutions can be neutralized with baking soda, soda ash, lime or household ammonia solutions. Flush neutralized acid with plenty of water