E. coli in Wisconsin well water
In Wisconsin, 4% of 1,091 private wells tested between 1997 and 2025 had E. coli above the Wisconsin limit (any detection) (n/a MPN/100mL), according to the UWSP Well Water Quality Viewer.
E. coli in a well means fecal contamination from septic systems, animals or surface water entering the well. It can cause serious gastrointestinal illness. Any detection is a failure.
Check your E. coli number
Type the value from your lab report. It is compared to the EPA limit, the same way the full interpretation does it.
Test your Wisconsin well for E. coli
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
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Systems that remove E. coli
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Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For E. coli
UV disinfection system
whole-house, at the point of entry, about $900
Fix the well cap and casing first; UV keeps bacteria from returning.
For E. coli
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
Rather have it installed and sized for your well? Book a free in-home water test with a licensed local company.
Where to get a well tested for E. coli in Wisconsin: certified labs, state programs and prices.
By county, from homeowner tests
Share of private wells above the state guidance level (n/a MPN/100mL) in tests homeowners sent to the state lab, 1999 to 2024.
Sources
- Wisconsin Well Water Quality Viewer samples: Private well samples compiled by the UWSP Center for Watershed Science and Education from the DNR Groundwater Retrieval Network, DATCP surveys, the UWSP Water and Environmental Analysis Lab and county health programs, published in the Wisconsin Well Water Quality Viewer with Wisconsin DHS. Samples are located to the town, village or city they fall in; one result per well and parameter (the latest) so repeat samples do not double count; wells without a state well number are keyed by location. Shares are against Wisconsin NR 140 enforcement standards (arsenic 10 ug/L, nitrate 10 mg/L as N, manganese 300 ug/L, lead 15 ug/L, copper 1.3 mg/L) and the iron and chloride secondary levels. Many samples were submitted by homeowners with a reason to test, so shares can run above a random survey. Retrieved September 9, 2026.