In some parts of the country the calcium and magnesium in water precipitate out and stick to the plumbing pipes, water heaters and even tea kettles as "scale." This can eventually clog pipes and interfere with heat conduction. The minerals that make water "hard" also interfere with the ability of soap to dissolve and lather, so you can end up with soap film on your skin and hair, clothes and dishes.
The solution is to install a water softener that gets rid of the calcium and magnesium via the exchange of ions with sodium or potassium ions in a bed of small plastic beads or through a chemical matrix called zeolite.
I recommend using potassium in the water softener, although I realize that it costs about three to four times more than sodium. Potassium is better for your health and better (though still not great) for the environment. However, even if you use potassium, I wouldn't drink water that has been through a water softener. While softened water is fine for bathing, I would use distilled water for drinking or cooking. There are many types of distillers readily available. The unit I recommend is the PW4HD3 (PureWater4Health.com, 520-303-1646) that can be mounted under the sink. It works silently, always produces cool water, and is self-sterilizing. Good distillers are a pricey investment, but over time they will save you money, particularly if you've been buying bottled water to avoid the contaminants in your tap water.
Andrew Weil, M.D.