Ion exchange works by filtering water through a synthetic or natural sand-like material called resin or zeolite. The resin is coated with positively charged sodium ions. As water flows through the unit, the resin exchanges its sodium ions for the positively charged calcium and magnesium ions. When the resin has absorbed its capacity in hardness minerals, the water softener must regenerate its ion exchange capacity. Robillard says most homeowners can choose between softeners that have programmable regeneration timers or demand-control models outfitted with regeneration sensors.
All water softeners require regular maintenance to function properly.
The resin can develop bacteria or fungi, or become clogged with mud. Iron deposits can clog the resin as well. It merely removes minerals that can be a nuisance. Softened water is an advantage if homeowners experience soap film on pots, utensils and skin, or find that detergents are not cleaning up to expectations. Water softening does raise the sodium level of water to about 7.5 to 8 milligrams per quart for every grain per gallon of minerals removed, which can be a health risk for people on low-sodium diets.