Drinking water plays an important role in the life of living organisms, including humans. Among the indicators that are used to determine the suitability of water for drinking is its hardness. The water hardness index is calculated by the presence of Ca2+ and Mg2+ salts in it. At high concentrations of these salts, water is considered hard. Negative influence on human health is carried out mainly by temporary hardness salts. In addition, the compounds Ca2+ and Mg2+ even under the action of temperature do not destroyed and disappear, but accumulate in the body. In water, the Ca2+ and Mg2+ cations can be combined together with the anions of the HCO3 - bicarbonate, SO2 - and sulfates, Cl-. Depending on which anions are present in water, the distinguish between temporary (carbonate) and constant (non-carbonate) water hardness