HTH™ pH Down helps balance pH levels in swimming pool water, improving both the quality of the water and the comfort of your swimmers. pH down not only ensures that your chlorine is working more efficiently, but it helps prevent scale formation on pool surfaces and equipment as well as significantly reduces skin and eye irritation. HTH™ pH Down is great for all pool types, including vinyl-lined pools and salt water systems.Use HTH™ 6-Way Test Strips or Test Kit to test your water weekly to make sure the pH level is between 7.2 and 7.8 ppm. If the pH measures above 7.8, add HTH™ pH Down directly to the pool water to decrease the pH. Swimming can resume immediately after treatment.