How a water softener works –
The ion exchange process of softening water is basically the same for all water softeners. Hard water contains calcium and magnesium ions. Water softeners use resin beads, which hold sodium ions. When hard water passes through the resin beads inside the softener, the beads attract and hold the calcium and magnesium ions and give off the sodium ions. After this ion exchange process, the water leaving the softener is soft. Once the resin bed is loaded with calcium and magnesium ions, it must be cleansed (or regenerated) so that it can continue to soften water. Salt water is used to wash the resin beads. The brine solution loosens the hardness ions, which have built up on the resin beads; then the system backwashes and flushes the hardness minerals away. Once again, the resin beads hold sodium ions, and the system is ready to soften more water.