The water to be softened flows through a resin filling in a pressure tank (softening bottles). The hardness-forming calcium and magnesium ions are absorbed by the resin and "soft" sodium ions are emitted into the water. Therefore this is called the ion exchange procedure. The previously hard water turns into soft water due to the exchange of hardness formers.
When the exchanger capacity is exhausted, the resin must be generated with concentrated saline solution. During regeneration, the resin takes on sodium ions and emits the previously collected calcium and magnesium ions to the flushing water. This flushing water is accordingly hard and will usually be discarded. Simple systems regenerate always at the same, adjustable time, time-controlled. The regeneration does not take place daily, but only when a specified water quantity has flown and the residual capacity is not expected to suffice for another day.
During regeneration, no soft water can be removed for approx. 120 minutes. Double pendulum softening plants consist of two softening bottles and provide soft water without interruption. While one bottle regenerates, the other bottle is in operation. The regeneration in this case is controlled consumption-dependently when the capacity is reached. Salt consumption for each regeneration is approx. 0.24 kg for each litre of resin (e.g. 6 kg for each regeneration in the case of the VEA25). Water consumption for each regeneration is approx. 10 litres for each litre of resin (e.g. 250 litres for each regeneration in the case of the VEA 25).