The determination of water hardness is carried out by means of complexometric titration with an eriochrome black indicator and EDTA at pH 9 according to DIN 38409. The water hardness range of 0.05 - 25 ° dH can be recorded by using different, specially adapted indicators.

Carbonate hardness is determined as alkalinity from acid/base titration to pH 4.3 (+m value) according to EN ISO 9963. The measuring range is 0.19 - 7.14 mmol/l (8.9 - 358 ppm CaCO3) depending on the reagents used. The determination of the - m value can also be performed and covers the range 0.05 - 0.5 mmol/l. Titration to pH 8.2 yields the +p value in the measuring range 0.1 - 15 mmol/l.  The m- and p-values are mainly used for the reliable control of boiler feed and boiler water in order to be able to comply with the requirements for water quality and corrosion behavior.