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Wisconsin Department of Health Services

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Drinking Water

Printable version of this factsheet (PDF, 115 KB)

Know Your Water Supply

Whether for drinking, cooking, bathing, or doing laundry, a supply of clean water is important to a healthy home. Know where your water comes from.

Tips for All Water Users

  • Install devices to prevent garden hose water from flowing backwards into your drinking water.
  • Consult your local building code office before making major repairs or changes to your plumbing system.
  • Conserve water because clean water is precious. Don’t waste it, instead, use water-saving toilets, and showerheads. Repair plumbing leaks right away.

Water Supply Problems

Bacteria and Viruses

The most common problem in private well water is bacteria (exit DHS; PDF, 70 KB). If bacteria are found, it means that human or animal wastes may be entering your water. Some bacteria can cause stomach upset or diarrhea.


Harmful chemicals such as gasoline, solvents, and pesticides can get into drinking water. Natural chemicals like arsenic, manganese, iron, and radon can also get into your drinking water.

Water Quality Testing

Public water supplies are tested for more than 100 chemicals. If you use public water you can call the water utility for information about your drinking water.

All private wells and many public water supplies use groundwater. Groundwater is water held in underground soils and rock.  Several communities use water from nearby lakes, like Lake Winnebago, Lake Michigan, and Lake Superior.

Tips for People who use Public Water Supplies

  • Find out where your water comes from. Contact your water utility if you have questions about your water supply.
  • Protect your water supply. Follow any water-use warnings. Dispose of pesticides, motor oil, and other chemicals properly. Reduce your use of lawn and garden chemicals since these chemicals may seep into drinking water.
  • Call your water utility if you have questions or if you notice a change in the taste, odor, smell or color of your water.

If you own a private well, be sure your water supply is safe. Yearly testing and maintenance will help protect your water supply. Call your local Department of Natural Resources (DNR) office for more information.

Tips for People who use Private Wells

  • Find out the age and depth of your well and the length of its casing (the pipe inside the drilled hole). Learn about the types of soil, bedrock and water supply problems in your area.
  • Find out when your drinking water was last tested. Know what tests were run, and the results. Keep records of any tests or repairs that you make.
  • Test at least once a year for bacteria. Several labs in Wisconsin can do these tests. Check the yellow pages in your phone book for a lab near you.
  • Test for nitrate. This is especially important if there is a pregnant woman or infant in your home. Nitrates come from fertilizer use, barnyard runoff, and septic systems. A high nitrate level may mean that your water also has bacteria or farm chemicals.
  • You may want to do other tests. Talk to a regional water supply expert at your local DNR office to find out if arsenic or radon are common in your area. If your well is near an old landfill, gas station, or buried fuel tank you might want to test for volatile organic chemicals (VOCs). If your well is near an orchard or farm field, a test for pesticides might be advised.
  • Have your water tested if you notice a change in its taste, odor, or color. Some tests are expensive and may be hard to do. Contact your well driller, local DNR office, or your local health department for help.
  • If your water contains bacteria or chemicals find out the source of the problem. Fix it and test the water again to be sure it is safe.
  • Keep chemicals, septic tanks, and animal waste away from your well. Dispose of chemicals and motor oil properly. Don’t put waste chemicals in your septic system. Limit your use of lawn and garden chemicals. Keep the area around your well clean.
For information on water quality, see the environmental health resources website on water issues or call 608-266-7480.

Prepared by the
Wisconsin Department of Health Services
Division of Public Health
Bureau of Environmental and Occupational Health

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Last Revised: March 20, 2014