Lead in Wisconsin well water
In Wisconsin, 3% of 7,937 private wells tested between 1994 and 2025 had lead above the Wisconsin enforcement standard (15 ug/L), according to the UWSP Well Water Quality Viewer.
Lead in well water almost always comes from household plumbing and older fixtures, not the aquifer, and corrosive (low pH) well water makes it worse. There is no safe level for children; it harms brain development.
Check your lead number
Type the value from your lab report. It is compared to the Wisconsin enforcement standard and the EPA limit, the same way the full interpretation does it.
Getting it fixed
Book a free in-home water test with a licensed local company, or see the treatment guide for what removes lead.
By county, from homeowner tests
Share of private wells above the state guidance level (15 ug/L) in tests homeowners sent to the state lab, 2018 to 2025.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Pepin | 97 | 9% | 1,436 ug/L | |
| Oneida | 102 | 8% | 65 ug/L | |
| Oconto | 35 | 6% | 77 ug/L | |
| Washington | 73 | 5% | 49 ug/L | |
| Clark | 74 | 5% | 33 ug/L | |
| Lincoln | 37 | 5% | 17 ug/L | |
| Juneau | 64 | 5% | 102 ug/L | |
| Calumet | 226 | 4% | 2,529 ug/L | |
| Chippewa | 545 | 4% | 789 ug/L | |
| Douglas | 161 | 4% | 67 ug/L | |
| Fond du Lac | 174 | 3% | 125 ug/L | |
| Monroe | 30 | 3% | 22 ug/L | |
| Marathon | 816 | 3% | 541 ug/L | |
| Washburn | 31 | 3% | 19 ug/L | |
| Wood | 67 | 3% | 30 ug/L |
Towns with the highest share above the state level
- Troy, St. Croix County10% of 31 wells
- Stettin, Marathon County8% of 36 wells
- Excelsior, Sauk County6% of 31 wells
- Mosinee, Marathon County6% of 48 wells
- Tilden, Chippewa County6% of 34 wells
- Anson, Chippewa County6% of 34 wells
- Eagle Point, Chippewa County6% of 52 wells
- Palmyra, Jefferson County5% of 40 wells
- Knowlton, Marathon County5% of 63 wells
- Koshkonong, Jefferson County5% of 86 wells
- Lafayette, Chippewa County4% of 45 wells
- Aztalan, Jefferson County4% of 47 wells
- Ixonia, Jefferson County3% of 90 wells
- Woodmohr, Chippewa County3% of 30 wells
- Hebron, Jefferson County3% of 36 wells
- Milford, Jefferson County3% of 36 wells
- Hudson, St. Croix County3% of 36 wells
- Stockton, Portage County3% of 40 wells
- Merrimac, Sauk County2% of 42 wells
- Jefferson, Jefferson County2% of 44 wells
- Caledonia, Columbia County2% of 44 wells
- Stockbridge, Calumet County2% of 45 wells
- Wheaton, Chippewa County2% of 49 wells
- Watertown, Jefferson County2% of 49 wells
- Chilton, Calumet County2% of 51 wells
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.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. lead counts and shares are listed on each county and town page with their sources.