Total hardness

Total hardness is not to be classified as a type of hardness, but as the sum of concentrations of calcium and magnesium ions present when these are both expressed as CaCO₃. If the water is alkaline, a proportion of this hardness, equal in magnitude to the total alkalinity and also expressed as CaCO₃, is considered as alkaline hardness, and the remainder as non-alkaline hardness. (See Figure 3.9.5)

Fig. 3.9.5
Total hardness