According to the state sanitary code, hardness shall be determined by calcium carbonate saturation or another method acceptable to the commissioner. Which water quality parameter does this describe?

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Hardness measures the concentration of multivalent calcium and magnesium ions in water. To express hardness consistently, we convert those ions to an equivalent amount of calcium carbonate, typically written as milligrams per liter of CaCO3. Describing hardness via calcium carbonate saturation (or an equivalent method approved by the commissioner) provides a standard way to quantify this mineral content as CaCO3. This is different from alkalinity, which reflects the water’s buffering capacity to neutralize acids; pH, which measures how acidic or basic the water is; and TDS, which sums all dissolved substances without focusing specifically on Ca and Mg. So the parameter described here is hardness.