Drinking water of good quality should neither be corrosive nor form scale. For this purpose, the pH of the water must be balanced to the calcium content in the water (see figure below). However, some treatments in the waterworks may cause the pH value in the water to rise above this equilibrium value. These equilibrium shifts occur, for example, after intensive aeration of ground water or after softening with rapid decarbonisation. The result is the formation of scale on downstream filters, pipelines and valves in the waterworks, or the pipeline network to the customers. To prevent this, pH control with acid is required.