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Well Water Testing

Safe, clean water is one of the most important substances in our lives. Wisconsin’s groundwater is normally free from bacteria, which are filtered out of the water as it seeps down through the soil. If you are on a municipal or community water system, the water is being tested regularly to ensure it is safe to consume. If you are a private well owner, it is up to you to test your water. Two very important tests a well owner should consider are for coliform bacteria and nitrate.

Coliform bacteria are a group of indicator bacteria or microorganisms that can be found in human and animal waste, in soil, on vegetation, and in surface water runoff. Most coliform bacteria do not cause illness, but may indicate a breach in the water system. If coliform bacteria are present in your well water, then other more harmful bacteria, viruses, and parasites may also be present.

It is recommended that you test your private well at least once a year for coliform bacteria. Even if your test results are OK one year that doesn’t mean your well won’t have contamination problems in the future. All state certified water testing facilities also test for E-coli when total coliform are present. If you have someone in the household who has serious health problems or a compromised immune system it is even more important that you test your water regularly. Any time you notice a major change in the taste, color, odor, or appearance of your water you should also test it.

Be sure to follow the directions for taking the sample that comes with your sample bottle. Your test result will come back as either Safe/Absent or Unsafe/Present bacteriologically. If coliform bacteria are present and your sample result is Unsafe, it is not cause for panic. A second test to confirm the first result may be in order. Have the well system inspected to determine if there is a logical reason for the unsafe result. Proper vermin-proof well caps can make a big difference in the safety of your water.

The most common treatment for unsafe well water is chlorination. This can be done by a professional or you can attempt it on your own depending on the type of well and well hookup you have. Visit for more information and instructions on well chorination.

Nitrate forms when nitrogen from fertilizers, animal wastes, septic systems, decaying vegetation and other sources combines with oxygenated water. If there are infants less than six months of age or women of childbearing age drinking the well water it is very important to test for nitrate. High levels of nitrate have been associated with a serious medical condition called blue-baby syndrome in infants and research suggests a connection to birth defects and miscarriages.

The EPA has established 10 mg/l (milligrams per liter) as the maximum contamination level. If a high level of nitrate is present in your well, contact a licensed well driller or water treatment specialist to research your options. If the level is below 10 mg/l but above 2 mg/l, you should monitor the level with a test annually. Levels that show a steady increase over time could indicate an outside influence such as heavy use of fertilizers or a nearby septic system that may be failing.

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