This paper presents a study of the influence of the mineral composition of water on its scaling potentiality. The importance of two metallic cations was studied: Fe(ii) and Mn(ii), which are often present in water. The water was prepared as either doped or not with the cation under study. The chosen concentrations were 0.2 or 2 mg/L for Fe(ii) and 0.05 or 0.38 mg/L for Mn(ii). Analytical tests were applied to the water with or without the metallic cation: doped water or control water. By comparison, it was possible to determine the significance of Fe(ii) or Mn(ii) in the crystallisation of calcium carbonate. Scaling risks were reduced when iron was present in the water—it brought about an increase in the formation of fine particles in the liquid. Unlike Fe(ii), Mn(ii) did not have a significant effect on the scaling power of the water.