Water softeners remove calcium and magnesium ions from water, making the water softer and therefore reducing damage to pipes and appliances, notes Windsor Salt. Hard water tends to leave behind damaging mineral deposits, as well as making soaps and detergents less efficient.
A water softener is a filtration device with a chamber called a mineral tank that contains resin beads or tablets. These beads carry a negative charge, while calcium and magnesium ions carry a positive charge. When the hard water passes through the mineral tank, the magnesium and calcium ions adhere to the resin beads and are thereby removed from the water, notes Popular Mechanics.