What amount of calcium chloride (100%) is necessary to increase calcium hardness by 10 ppm in 10,000 gallons of water?

To determine the amount of calcium chloride required to raise the calcium hardness by a specific amount, a standard formula can be applied. For a body of water such as a swimming pool, it is known that to increase the calcium hardness by 10 ppm in 10,000 gallons of water, approximately 1 pound of calcium chloride is needed.

This calculation is rooted in the relationship between the concentration of calcium ions in the water and the volume of water being treated. When calcium chloride is added, it dissolves in the water, increasing the level of calcium hardness directly proportionate to the amount added.

In this question, the specific increase desired is 10 ppm, which refers to parts per million—a common unit of measurement used in water chemistry to indicate the concentration of a substance within the water. The formula typically used for calculating the amount of calcium chloride is based on standard treatment protocols that have been established through empirical research and practical experience in pool maintenance.

Thus, to achieve an increase of 10 ppm in 10,000 gallons, 1 pound of calcium chloride is correct, as it aligns with established guidelines and calculations in water treatment practices. This information is critical for swimming pool operators to ensure the water is maintained at safe and healthy levels for swimmers.