Hardness, carbonate hardness, sawn hardness, what else!? WATER HARDNESS! But don't worry, WATER HARDNESS is just a more general term for the hardness or total hardness in water. We remember: Hardness consists of carbonate hardness and non-carbonate hardness, which means it is the sum of the calcium and magnesium ions, which are present as hydrogen carbonates or carbonates, and the chlorides, nitrates, sulfates, etc.