Shock level for a pool with a CYA of 70 is 20ppm. In a 21K gallon pool, each gallon (4 quarts) of 6% bleach will add about 3ppm of chlorine. Each gallon of 8.25% bleach will add 4ppm. Use that info to help you figure out how much chlorine to add each time you test to get the chlorine level back up to 20.
Bookmarks