Hard water contains calcium, magnesium, and other dissolved minerals. The water is safe to drink, but it can leave a residue on showers and dishes, and deposits inside appliances that use hot water. Over time, that buildup can affect performance and efficiency.

Hard water can quickly clog a point-of-use filter, so you’ll need to use a whole-house water softener. Ion exchange systems, the most common, work by replacing water-hardening minerals with soft sodium ions…Even if your water is very hard, the amount of sodium left behind in softened water should be low. But if you’re concerned, consider choosing a system that uses potassium chloride. They’re usually just as effective at softening water, though potassium chloride costs several times more than sodium chloride to replenish.

Excerpt taken from Consumer Reports Magazine, February 2012.