Water softening

Water softening reduces dissolved calcium and magnesium that cause hardness, either by removing these ions or replacing them with others, commonly sodium.

Ion exchange: A process that swaps ions between a solution and a solid material. Household softeners commonly exchange calcium and magnesium for sodium on resin beads.
Water hardness: The concentration of dissolved multivalent ions, chiefly calcium and magnesium, in water. Softening targets the mineral content that defines hardness.
Water softener: A device that reduces water hardness, commonly through ion-exchange resin. This appliance applies ion exchange to soften water in homes and businesses.
Water filtration: The separation of suspended or dissolved substances from water using a porous medium. Ordinary particle filtration does not necessarily remove dissolved calcium and magnesium.
Hard water: Water containing substantial dissolved calcium and magnesium ions. Its effects on scale and cleaning motivate many softening treatments.
Lime softening: A chemical treatment that adds lime to precipitate dissolved minerals from water. Municipal plants use it to precipitate calcium and magnesium rather than exchange them.
Calcium: A chemical element whose dissolved ions are a major cause of water hardness. Calcium is one of the principal ions removed or exchanged during treatment.
Scale (mineral deposits): A hard mineral deposit that forms when dissolved substances precipitate from water. Reducing hardness can limit scale inside pipes, boilers, and heating elements.
Water desalination: The removal of dissolved salts from water to produce water with lower salinity. Desalination removes a broader range of salts than hardness-focused treatment.
Soft water: Water with low concentrations of dissolved calcium and magnesium ions. This is the treated water produced when hardness is sufficiently reduced.

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