Robelle Total Alkalinity Control is used when pH levels fluctuate widely over a short period of time. A low total alkaline reading is also indicative of corrosive pool water, a blue or green cast to the water and difficulty in holding chlorine residuals. Low alkalinity can cause equipment and plaster damage. If the alkalinity is too low or too high, the pH of the pool water will be difficult to maintain in the proper range. This product raises the total alkalinity in swimming pool water. It boosts the effectiveness of your pool water disinfectant, as well as aids in the prevention of scale formation, metal corrosion and the etching of pool surfaces. It helps maintain your pool's pH level and eliminates pH bounce. Easy to use and dissolves quickly. Test for total alkalinity with a reliable test kit. The desired range for total alkalinity is as follows: Fiberglass Pools 70-100 ppm. Marcite, Painted, Tile, or Exposed Aggregate Pools 80-120 ppm. Vinyl Pools 120-140 ppm .