Hardness

In the context of water treatment, the term “hardness” refers to the concentration of dissolved calcium and magnesium ions in water. These minerals contribute to water hardness and can be present in the form of dissolved calcium carbonate (limestone) and magnesium carbonate.

Water hardness is typically measured in units such as milligrams of calcium carbonate per liter (mg CaCO₃/L) or in degrees of German hardness (°dH), where 1 °dH corresponds to 10 milligrams of calcium oxide (CaO) per liter of water. A higher hardness level indicates a greater concentration of calcium and magnesium ions, making the water “harder.”