Sodium content when softening by ion exchange

When the water softener is in operation, it exchanges the calcium and magnesium hardness-forming elements for sodium. This means that for each degree of hardness softened, 8 mg of sodium is exchanged and added to the water. The limit value of the drinking water regulations must be observed. This is 200 mg/l of sodium. For water hardnesses of up to 30 ° dH, this limit value is generally not exceeded.

Calculation example 20 °dH: The water hardness is 20° dH and should be reduced to 4° dH. This means that 16 °dH is removed and 16 x 8 mg = 128 mg sodium is added. This value is far below the limit.

Very high water hardness from about 30° dH

Calculation example 30 °dH: The water hardness is 30° dH and should be softened to 4° dH. This means that 26 °dH is removed and 26 x 8 mg = 208 mg of sodium is added. Added to this is the sodium value already contained in the water, which can be taken from the supplier's water analysis. If this is 20 mg/l, for example, the total value in this calculation example would be 228 mg/l of sodium. The limit value of the drinking water regulations would be exceeded.

As a remedy, the residual hardness is not regulated to 4° dH but to 10° dH. Then only 20° dH is softened and the sodium load is reduced to 160 mg/l. Adding the assumed 20 mg/l results in a total sodium content of 180 mg/l. The limit value of the drinking water regulations is complied with.

If you have us install and commission the water softening system, our fitter will take this calculation into account and adjust the system accordingly.

Dosing systems as a supplement

To ensure that no limescale problems arise due to the residual hardness, a dosing system with appropriate hardness stabilizers can also be used. These largely prevent limescale formation in the water. Dosing is proportional to the quantity and is approved for drinking water. The values given here in the calculation examples must be replaced by the actual values.

If you have any questions, please contact us; we will be happy to advise you individually.