Actions to take if your well has bacteria:
- Do not drink the water.
- Use a safe water source.
- Take a confirmation sample.
- If confirmed, disinfect your well.
- Wash dishes properly.
- Monitor your well.
Review our Bacteria in Private Well Water (P-02132 - English, Spanish, Hmong) fact sheet for more details on these steps and the Department of Natural Resources' (DNR) brochure about bacteria in wells for more information on sources and follow-up steps.
Contamination with bacteria can occur when work is done on the well; if the well was not built properly; or if nearby animal or septic system waste enters the groundwater.
Test your well annually
All private, residential wells should be tested at least once a year for bacteria (total coliform and E. coli) and whenever changes in water quality are noticed. Bacteria testing looks for indicators of contamination by harmful microorganisms. If bacteria are present, water can pose an immediate health risk to everyone.
Bacteria in the well can cause flu-like illnesses, leading to diarrhea, nausea, vomiting, cramps, or fever. Young children, the elderly, and people with weakened immune systems are more likely to be impacted than others.
Read what's happening across the state to address bacteria issues in groundwater.
Sometimes bacteria is from manure contamination
Manure contamination of well water is a serious short-term health risk because it means that illness-causing bacteria and other germs can be in the water. Every year, a number of residential wells in Wisconsin are contaminated by manure and agricultural runoff. When this happens, people may notice changes in water quality, such as changes in the taste, color, smell, or look of the water.
Manure-related problems are usually caused when liquid manure is spread on fields during the late winter and early spring months. During these times, manure cannot be tilled in, or adequately absorbed by, the soil.
We have general information about manure contamination (P-45088) of residential wells and testing for bacteria. Be sure to take specific steps (P-01096) if your well, or a nearby well, is contaminated by manure. Talk to your doctor if you have specific health concerns or if you or a family member have diarrhea, nausea, vomiting, cramps, or fever that you believe is related to your well.
Questions? Can't find what you're looking for? Contact us!