This is a dry granular product that increases the total hardness in pool water to the recommended range.Test for calcium hardness with a reliable test kit. The desired range for calcium hardness is as follows: Vinyl Pools: 200-300 ppm, Tile and Exposed Aggregate Pools: 200-400 ppm, Marcite, Fiberglass or Painted Pools: 250-400 ppm. If the calcium hardness tests less than the desired range, add this product according to the included chart. Place this product into a plastic bucket already filled with swimming pool water. Do this in a ration of up to 2 pounds of product per approximate 5-gallon bucket of water. Slowly pour this solution around the perimeter of the swimming pool while the circulating system is operating. In a 10,000 gallon pool, do not add more than 10 pounds of this product per 2 hour period.