Water that contains significant minerals (calcium, magnesium, etc.) is called hard water. It affects all public water supplies in California. Hard water clogs pipes and counteracts the effects of soap and detergent.

Water softeners remove the minerals that cause water to be hard by a process of ion exchange. Softeners can be automatic, semi-automatic, or manual. They collect hardness minerals in a conditioning tank and from time flush them away. Softened water is much more healthy and pleasant for bathing and cleaning than hard water, and will greatly extend the life of copper pipes.