How many mg/L of calcium carbonate defines water as “hard”?

Water is defined as "hard" when it contains a certain concentration of dissolved minerals, primarily calcium and magnesium. The threshold for classifying water as hard varies, but a common standard indicates that water with more than 100 mg/L of calcium carbonate (CaCO3) is generally considered hard.

When the concentration of calcium carbonate reaches 100 mg/L, it signifies a level of hardness that may influence various aspects, including soap performance, scaling in pipes, and general water quality. This measurement is essential for water treatment professionals and helps classify water quality for different uses, whether for drinking, irrigation, or industrial processes.

Understanding these thresholds is critical in the water treatment field, as it guides decisions about water softening and other treatment methods to ensure suitability for specific applications.