This document discusses ion exchange water softening. Hard water contains calcium and magnesium ions that cause scaling. Ion exchange softening works by exchanging sodium ions on resin beads for calcium and magnesium ions, reducing hardness. When resin is saturated, it is regenerated using a brine solution to restore the sodium ions. Water softeners come in manual, semi-automatic, fully automatic, and demand-initiated models and provide benefits like extending appliance life and reducing detergent and fuel costs.