How is water hardness typically measured?

Water hardness is commonly measured in milligrams per liter (Mg/L) or grains per gallon (GPG). This measurement reflects the concentration of divalent metal ions, primarily calcium (Ca²⁺) and magnesium (Mg²⁺), that contribute to the hardness of water.

Using Mg/L allows operators to express hardness in a metric system, which is widely used in scientific contexts. On the other hand, grains per gallon is often used in practical applications, particularly in water treatment and household contexts in the United States. One grain per gallon is equivalent to approximately 17.1 Mg/L, offering a way to convert between metric and imperial systems, which can be beneficial depending on the context of water usage and treatment.

Other measurement units, such as parts per million (PPM), micrograms per liter (μg/L), and ounces per gallon (OPG), are less common for assessing water hardness specifically. While PPM can be related to concentrations, it is not the standard for expressing hardness. Micrograms per liter is used for trace contaminants rather than hardness assessment. Ounces per gallon is more relevant for different measures of concentration and is not typically applied in the context of water hardness measurements. Thus, the most relevant and accepted