When and how to soften
Calcium and magnesium, two minerals that make water hard, can form deposits in pipes and water heaters and react with soap to leave a residue on laundry and dishes. To find out how hard your water is, ask your utility or have a plumber or a water-treatment company analyze it. Some Cooperative Extenstion agents also test water.
Consider softening water of more than 9 grains per gallon of hardness. To soften all indoor water or just the hot water, you can install an ion exchange softening tank that replaces calcium and magnesium ions with sodium ions. (A person on a low-sodium diet should consult his physician before drinking softened water.) Such systems can be purchased or rented.
To soften water in a washing machine only, add a packaged softener or water conditioner. Where permitted, polyphosphate types are the best. Put in the softener before adding soap or detergent. Add more softener to the rinse if water is very hard.