The ion-exchange process
Hard water flows through a tank filled with tiny resin beads carrying sodium ions.
Calcium and magnesium in the water are strongly attracted to the beads and stick to them, releasing sodium in exchange.
Softened water leaves the tank and flows into your home's plumbing.
When the resin fills up with hardness minerals, the softener automatically flushes itself with a brine solution and starts over. This is called regeneration.