Directions: Test your pool water. Per the manufacturer: in vinyl and fiberglass pools, calcium hardness levels should be between 150 – 250 ppm and in pools with plaster or similar surfaces, calcium hardness levels should be between 250 – 350 ppm. If your pool water calcium hardness is low, determine the dosage needed to increase to the correct level. 2 oz per 1,000 gallons of pool water will increase calcium hardness by 10 ppm. Doses over 3 lbs should be split into thirds. Allow pool water to circulate 12 hours between treatments to prevent clouding. DO NOT OVER TREAT since there is no easy way to remove calcium hardness without dilution with fresh water.