WATER HARDNESS
If you thought that water is just water then think again. It contains substantial amounts of calcium and magnesium, and the total content of these metal ions is converted into something called water hardness. Hardness of water is different in many different places in the world, and even local variations are common. What does the water hardness interfere with? Too much of it will give you, among other things, less soft bread and less colored cooked vegetables. Also, hard water makes the tea cloudy and foamy and does the same to coffee, as the calcium carbonate precipitates. If such things are bothering you, invest in a good water filter that reduces the water hardness.