Test sets according to the limit value method allow a very simple and quick determination of the water content. Total hardness and carbonate hardness are detected as water constituents. The addition of a single drop of indicator determines whether the water hardness is above or below the limit value. The determination is carried out without waiting directly after the addition of the indicator and its evenly submixed by shaking. By selecting the appropriate indicator, the limit value for which the sample water is to be tested is determined.