Water softeners consist of three main components: a mineral tank, a brine tank, and a control valve. In some smaller units, the mineral tank and brine tank are combined into one cabinet.
Professionals install whole-home systems at the point of entry of the main water line. Smaller units are installed under sinks or near a washer—these units only soften the water for that fixture, not the entire home.
- Mineral Tank: Hard water passes into the mineral tank through resin beads, and an ion exchange occurs. Magnesium and calcium ions are exchanged for sodium or potassium ions from the brine tank. 
- Brine Tank: The brine tank contains sodium or potassium to recharge the resin. 
- Control Valve: The control valve determines when to clean the resin beads.