Water hardness and composition
The hardness represents the amount of calcium and magnesium dissolved in the water.
Water hardness is generally expressed in French degrees (°f or °fH).
1 French degree (°f or °fH) is equal to
Lime scale = calcium carbonate (CaCO3)
Water hardness scale:
from 0 to 5°fH: very soft water
from 5 to 15°fH: soft water
from 15 to 25°fH: medium hard water
from 25 to 40°fH: hard water
> to 40°fH: very hard water