ABSTRACT: The total hardness of water which is used for textile washing varies strongly worldwide. It differs partially by a multiple within a municipality. An optimum washing result in a minimum of water and detergent consumption assumes an accurate knowledge of the total hardness of water. This paper discusses a new measurement procedure by which the total hardness of water can be determined during the washing process. Two sensors of different materials were used. The results obtained from the measurement provide the basis for an automated and optimal dosage.