Water softeners are specific ion exchangers that are designed to remove ions, mainly positively charged calcium (Ca2+) and magnesium (Mg2+) ions. A water softener collects hardness minerals within its conditioning tank and from time to time flushes them away. Softeners are also able to remove up to 5 ppm (mg/L) of clear water (dissolved) iron.
Process: The water enters the house and passes through a bed of small plastic resin beads. The resin beads are covered with salt ions. As the water flows past the salt ions, they are exchanged with the calcium and magnesium ions. Eventually, the resin beads contain nothing but calcium and magnesium and no longer soften the water. Then it is time to regenerate the resin beads.