**3. Methods for measuring and characterizing stabilized water**

Individual parameters are not sufficient enough to predict the corrosivity of water and a number of indices have therefore been developed that look at the relationship of these parameters in an attempt to quantify the corrosivity or aggressivity of the water. The majority of these are based on the observation that if the water is aggressive to calcium carbonate, it will also be aggressive to other materials of construction. Furthermore, if conditions are such to encourage the precipitation of calcium carbonate, then this can be used to form a protective calcium carbonate film on the surface of the infrastructure, then this could be considered an effective strategy to mitigate corrosion. As a result most indices use the dissolution or precipitation of calcium carbonate as the basis to determine the stability of the water. This does not however tell the whole picture as water can still be considered corrosive despite having a positive Calcium Carbonate Precipitation Potential (CCPP). The Larson-Skold Index (LI) stands out as the only index that look at other factors such as concentrations of chloride and sulfate ions and their impact on the corrosivity of water to iron and steel pipe, and therefore should always be considered on top of a calcium-carbonate based indices. The most common indices are described below.
