In order to be able to explain this term, let us recall carbonate hardness once again: Carbonate hardness refers to the calcium and magnesium ions dissolved in water and accounts for the largest proportion of the total hardness of the water. If these calcium and magnesium ions are now removed, this is referred to as decarbonization or partial desalination of the water. Why only partial desalination? It's simple: Although the hardener calcium carbonate is removed, there are still other hardeners left behind, such as sulfates or chlorides.