Hydrochloric Acid, also known as muriatic acid, is a strong, corrosive acid commonly used in swimming pools to lower the pH and total alkalinity of the water. If the pool's pH rises above the ideal range (7.2–7.6), chlorine becomes less effective, and scale or cloudy water may form. Adding hydrochloric acid helps bring the pH down to a balanced level, ensuring the sanitizer works efficiently and the water remains clear and safe. This acid also plays a role in cleaning pool surfaces, especially removing mineral buildup and stains from tiles or grout. It must be handled with extreme care—always added to water (never the other way around), and with protective gloves and eyewear. Since it's highly reactive, dosing should be done in small amounts, followed by retesting the water after circulation. Proper storage in a cool, ventilated area away from other chemicals is crucial for safety.