Copper in Wisconsin well water
In Wisconsin, 1% of 7,890 private wells tested between 1996 and 2025 had copper above the Wisconsin enforcement standard (1.3 mg/L), according to the UWSP Well Water Quality Viewer.
Copper leaches from pipes when water is acidic. Above 1.3 mg/L it causes stomach upset, and long-term exposure can harm the liver and kidneys. Blue-green stains on fixtures are the giveaway.
Check your copper 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 copper.
By county, from homeowner tests
Share of private wells above the state guidance level (1.3 mg/L) in tests homeowners sent to the state lab, 2005 to 2025.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Lincoln | 37 | 11% | 2.84 mg/L | |
| Trempealeau | 74 | 7% | 2.8 mg/L | |
| Washburn | 31 | 6% | 1.41 mg/L | |
| Sauk | 347 | 6% | 15.9 mg/L | |
| Clark | 71 | 6% | 6.5 mg/L | |
| Manitowoc | 61 | 5% | 5.32 mg/L | |
| Kewaunee | 58 | 3% | 4.66 mg/L | |
| Lafayette | 30 | 3% | 2.96 mg/L | |
| Door | 167 | 3% | 3.17 mg/L | |
| Oneida | 103 | 3% | 1.74 mg/L | |
| Calumet | 226 | 3% | 3.98 mg/L | |
| St. Croix | 270 | 3% | 2.52 mg/L | |
| Vilas | 78 | 3% | 2.42 mg/L | |
| Crawford | 39 | 3% | 1.5 mg/L | |
| Langlade | 40 | 3% | 1.66 mg/L |
Towns with the highest share above the state level
- Excelsior, Sauk County9% of 32 wells
- Stockbridge, Calumet County7% of 45 wells
- Troy, St. Croix County6% of 31 wells
- Wheaton, Chippewa County4% of 49 wells
- Harrison village, Calumet County3% of 30 wells
- Tilden, Chippewa County3% of 34 wells
- Cooks Valley, Chippewa County3% of 40 wells
- Lafayette, Chippewa County2% of 45 wells
- Dekorra, Columbia County2% of 47 wells
- Waterloo, Jefferson County2% of 49 wells
- Koshkonong, Jefferson County1% of 86 wells
- Ixonia, Jefferson County1% of 90 wells
- Oakland, Jefferson County0% of 78 wells
- Lake Mills, Jefferson County0% of 65 wells
- Knowlton, Marathon County0% of 63 wells
- Concord, Jefferson County0% of 54 wells
- New Glarus, Green County0% of 54 wells
- Sullivan, Jefferson County0% of 54 wells
- Farmington, Jefferson County0% of 53 wells
- Eagle Point, Chippewa County0% of 52 wells
- Hull, Portage County0% of 52 wells
- Chilton, Calumet County0% of 51 wells
- Watertown, Jefferson County0% of 49 wells
- Mosinee, Marathon County0% of 48 wells
- Aztalan, Jefferson County0% of 47 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. copper counts and shares are listed on each county and town page with their sources.