Well water in Milwaukee County, Wisconsin
In Milwaukee County, <1% of 153 private wells tested between 1989 and 2025 had nitrate above the Wisconsin enforcement standard (10 mg/L), according to the UWSP Well Water Quality Viewer.
153 private wells tested 1989 to 2025 in state summaries; 11 individual samples from 7 wells, 1947 to 1995. Data refreshed September 9, 2026.
What homeowner tests found
Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 1989 to 2025. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA. County and state figures combine the town summaries, weighted by wells tested; medians are not combined.
What individual samples found
Each row summarizes every public sample for that contaminant inside Milwaukee County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Uranium 1954 to 1983 | 11 | 64% | 0% | 0.4 | 0.9 | 30 ug/L EPA limit |
Sampled fewer than 10 times, too few to summarize: Radium (226 + 228) (5), Fluoride (4), Arsenic (1), Nitrate (1), Lead (1), Iron (4), Sodium (2), Manganese (2), Radon (1), Chloride (1).
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What this means
Among homeowners in Milwaukee County who sent a sample to the state lab, the health-based limits most often exceeded were nitrate (<1% of 153 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.
What to test for in Milwaukee County
- Volatile organic compounds (VOCs)2,147 leaking underground storage tank sites on record locally.
- Nitrate<1% of 153 local wells tested were above the Wisconsin enforcement standard.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 180 pCi/L.
- FluorideDetected in 100% of local samples.
- IronDetected in 100% of local samples.
- ManganeseDetected in 100% of local samples.
- ChlorideDetected in 100% of local samples.
Contamination sources on record in Milwaukee County
Wisconsin DNR records 2,147 leaking underground storage tank sites in Milwaukee County, among 6,277 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 2,147
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 101
- lined landfills and transfer facilities
- 4,029
- other remediation projects
Treatment that fits the local profile
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
- Chloride
- Point-of-use reverse osmosis; Distillation
Get your Milwaukee County water tested at home
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Common questions
Is there arsenic in well water in Milwaukee County?
Arsenic was detected in 100% of 1 public well samples in Milwaukee County, and 0% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Milwaukee County?
The median radon level across 1 public samples in Milwaukee County was 180 pCi/L, with a high of 180 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Milwaukee County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Towns in Milwaukee County
- Franklin0% nitrate
18 towns have fewer than 30 public samples and are included in the Milwaukee County totals above rather than shown separately: Bayside village, Brown Deer village, Cudahy, Fox Point village, Glendale, Greendale village, Greenfield, Hales Corners village, Milwaukee, Oak Creek, River Hills village, Shorewood village, South Milwaukee, St. Francis, Wauwatosa, West Allis, West Milwaukee village, Whitefish Bay village.
Sources
- USGS Water Quality Portal: 33 samples in Milwaukee County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- Wisconsin Well Water Quality Viewer samples: summaries for 2 contaminants in Milwaukee County, up to 153 wells each. 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.
- Wisconsin DNR regulated sites: 6,277 regulated sites located in Milwaukee County. Open and closed remediation activities (BRRTS, including leaking underground storage tanks and spills) and landfill and waste sites from the Wisconsin Department of Natural Resources. Retrieved September 9, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.