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Test your private well water annually

Make sure you're serving your family safe drinking water. While most private water wells in Wisconsin provide safe drinking water, some may become contaminated with bacteria and other contaminants that are not filtered out when the water soaks into the ground. Take action immediately if you suspect there is a problem with your water or if you notice a water quality change.

Recommended testing

DNR recommends you test your private well at least once a year for coliform bacteria contamination and any time you notice a change in how the water looks, tastes or smells. Even if your water looks, tastes and smells good, it can contain harmful bacteria and viruses. For more information, see Bacteriological Contamination of Drinking Water Wells [PDF]

Laboratories certified to test drinking water

Contact a certified laboratory that can test your water for a specific contaminant.

Proper water sample collection

Collecting a water sample for testing isn't as easy as turning on the tap. In fact, well owners frequently get false positives because they do not properly collect the sample or get it to the laboratory within the 48 hours required for an accurate test. Your test results and the next steps you take differ by contaminant.

The laboratory you work through will provide you with a water sampling kit. It's very important to make sure you follow their sampling directions.

Watch a demonstration showing the DNR's recommended methods for of how to properly collect a water sample that will yield accurate results.

Understanding test results for bacteria, nitrates and arsenic
  • Stop drinking your water if the lab report indicates that bacteria is present in your water sample. Bacteria present in water is an indication that disease-causing bacteria may be present in the water. For more information, see Bacteriological Contamination of Drinking Water Wells [PDF].
  • If the lab reports elevated levels of arsenic (greater than 10 parts per billion (ug/l)), you may want to stop drinking the water. For more information, see Arsenic in Drinking Water [PDF].
  • If the lab reports elevated levels of nitrates (greater than 10 parts per million (mg/l)), avoid drinking the water if you're pregnant and stop giving the water to infants younger than six months or using the water to prepare infant formula. For more information, see Nitrate in Drinking Water [PDF].
Other contaminants

If the lab reports elevated levels of other contaminants, follow the steps described in the brochures for that particular contaminant. For more information, see frequently asked questions about water quality and contamination in private wells.

You may want to test for other contaminants, like nitrate, arsenic or agricultural chemicals.

The U.S. Geological Survey and UW Steven's Point can help you understand what water quality is like in your county and contaminants you may want to test your water for.

What's wrong with my water