We have already talked so much about carbonate hardness and hardeners that it is high time to finally address the TOTAL HARDNESS: When we talk about the TOTAL HARDNESS (GH) of water, we mean the alkaline earth ions calcium and magnesium dissolved in the water, sometimes also barium and strontium. The more of them there are, the harder the water is. If you have a water bottle next to you right now, check the label to see how many minerals are in your water and whether it is hard or soft water. By the way, the unit of TOTAL HARDNESS is mmol/l; in the past, the degree of German hardness was used. (°dH). 1 °dH corresponds to 10 mg CaO/l.