An ion is an electrically charged atom or group of atoms. A cation is a positively charged ion. This exchange occurs in a resin bed during the softening cycle. The beads attract and hold positively charged ions such as sodium, but will exchange them whenever the bead encounters another positively-charged ion such as calcium or magnesium. Brine Tank - This tank holds the dissolved salt solution that is necessary to regenerate the resin.
Regeneration refers to reversing the ion exchange operation.
The magnesium and calcium ions are driven off of the resin beads and replaced by positively charged sodium ions. The regeneration occurs when the resin beads are washed with a strong salt water solution. The salt forces the calcium and magnesium ions to be released, and they are then discharged as waste during the backwashing cycle. The beads are ready to once again attract hardness ions from the water. Many installed water softeners are fully automatic.