Your conditioner’s resin tank contains thousands of tiny resin beads. These beads hold minute electronically charged ions. When freshly regenerated, these beads are full of sodium ion from softening salt. As the hard and iron water passes through your conditioner, the hard water ions are attracted to the resin beads. There, ions of sodium are exchanged for the hard water ions. The result is soft iron free water. After several days, the beads become full of the hard water ions and can no longer soften the water. However, when your conditioner regenerates again, the beads are replenished with more sodium ions, leaving you with conditioned water.