Answer: 150-250 ppm
Explanation: The sum of all the calcium dissolved in water is referred to as the calcium hardness. Calcium is important since high levels are unstable and become even more unstable if the pH or the total alkalinity rise above the normal levels. These imbalances can result in cloudy water and/or scale. In addition, calcium does not like warm water. As water temperature rises, calcium becomes more likely to precipitate out of solution. Calcium is actually more soluble in cold water, which is why scaling of heater equipment is so common.