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How a water softener works

The water softener is a simple device to reduce the hardness of water.
Water hardness

• The hardness of water depends on the concentration of calcium (Ca 2+) and magnesium (Mg 2+ ) ions in the water.

• It is measured by its total hardness (TH) expressed in French degrees (°f).

• 1 French degree is equivalent to 10 mg of calcium carbonate per litre of water.

• Water hardness is not subject to standards since there is no known toxicity for man.

Hardness indicator :
Range of total hardness :

less than 8°f
- Very soft water
- Softening not essential
8 to 15°f
- Soft water
- Softening advisable
15 to 30°f
- Medium hard water
- Softening recommended
30°f and above
- Very hard water
- Softening essential

Guide to the hardness of water by region:
(Source: French Ministry of Health– DDASS Sise-Eaux)

See the pdf
How a water softener works

• Water softening is a process involving exchanging calcium and magnesium ions, responsible for water hardness, for sodium ions.

• Ion exchange is performed using a resin (composed of small beads) initially charged with sodium ions.

• When this resin is brought into contact with hard water, the calcium and magnesium ions bind to the resin by taking the place of the sodium ions which were originally there. These sodium ions are then released into the water. This gives softened water.