If water supply in your home is through municipal water company, you can call the municipal offices and ask for hard water test results. If they provide information of minerals in PPM (parts per million), just note it down and divide this number with 17.1 to get GPG (grains per gallon).
If any private water supply company serves water in your house, you may have to test for hardness of water yourself. Some health departments offer testing. Check if any such service is available in your area. If it is not, get the water tested by a reliable independent water-testing lab or a water-conditioning company. Some of these companies offer free testing but in return they try to sell some equipment to you. In most cases you may not need these equipments.
How to Find How Hard is Your Drinking Water
You can find out independent water testing labs from your water utility or the state health department. You can also look for “Laboratories” in the telephone directory or explore and find it out on the Internet. National Testing Laboratory is a good and affordable testing option. Following are details of this mail-order laboratory:
Tel No.: (800) 458-3330:
Testing Cost: $137 to test 77-item check of inorganics, including hardness minerals; $167 to test additional 20 pesticides, herbicides, and PCBs.
Another good lab is Suburban Water Testing, (800) 433-6595 (http://www.h2otest.com)
Many softener companies will test a mailed-in water sample for free. Some other softener companies give free do-it-yourself test-strip kit. Look for these. These hard water test-strip kits are also available in most stores selling water softeners and home appliances.
If you have a well, do the test for hardness and safety. I recommend testing your well water every 6 months for mineral content, lead, and radon, bacteria and nitrate and other contaminants in well water. If you need help, you can contact your local health department for recommendations.