How is hard water quantified in terms of its content?

Hard water is quantified primarily by measuring the concentration of calcium carbonate (CaCO3) present in the water. The presence of calcium and magnesium salts, which contribute to hardness, is most commonly represented in terms of calcium carbonate equivalents. This is because calcium carbonate is a standard reference point that provides a clear understanding of the overall hardness of water, making it easier to compare and communicate the hardness levels across different water sources.

Using calcium carbonate as the reference allows water quality professionals to establish guidelines and standards for water treatment processes. In contrast, other compounds such as sodium chloride and calcium sulfate do not specifically reflect the hardness of water, as they serve different functions in water chemistry. Total dissolved solids encompass all dissolved substances in water and do not specifically target the hardness caused by calcium and magnesium ions, making it a broader measure that is less useful for quantifying water hardness specifically.