Well water in Oconomowoc, Wisconsin
In Oconomowoc, 3% of 249 private wells tested between 1990 and 2025 had nitrate above the Wisconsin enforcement standard (10 mg/L), according to the UWSP Well Water Quality Viewer.
249 private wells tested 2023 to 2023 in state summaries; 37 test results across 6 contaminants from at least 3 wells, 1963 to 1972; chloride has the most at 7. Data refreshed September 9, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
What homeowner tests found
Wisconsin Well Water Quality Viewer samples: private wells tested and reported to the state, 2023 to 2023. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.
Closer than the town
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among homeowners in Oconomowoc who sent a sample to the state lab, the health-based limits most often exceeded were nitrate (3% of 249 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 Oconomowoc
- 1Nitrate3% of 249 local wells tested were above the Wisconsin enforcement standard.
- 2Coliform bacteriaRecommended for every private well, every year.
- 3FluorideDetected in 100% of local samples.
- 4ChlorideDetected in 100% of local samples.
- 5ManganeseDetected in 100% of local samples.
- 6IronDetected in 100% of local samples.
- 7Volatile organic compounds (VOCs)14 leaking underground storage tank sites on record locally.
Test your Oconomowoc well for nitrate, coliform bacteria and fluoride
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
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
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Where to get a well tested in Wisconsin: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Oconomowoc numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Oconomowoc
Cambrian-Ordovician aquifer system
Sandstone. Sandstone wells draw from pore space in the rock and tend to be dependable. Iron, manganese and hardness are common, and some sandstones carry arsenic or radium, so a first test should include both.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the town centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Wisconsin
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Wells, Wisconsin DNR
- Laboratory Certification, Wisconsin DNR
Contamination sources on record in Oconomowoc
Wisconsin DNR records 14 leaking underground storage tank sites in Oconomowoc, among 43 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.
- 14
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 5
- lined landfills and transfer facilities
- 24
- other remediation projects
Treatment that fits the local profile
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Systems we would look at first
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For manganese
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Oconomowoc
No water treatment company serves Oconomowoc through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Oconomowoc, and you get an email naming it first.
Common questions
How often should I test a private well in Oconomowoc?
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 near Oconomowoc
Closest first. Groundwater does not stop at a line on a map, so the next town over is a fair second opinion.
Want the numbers themselves? Download the Wisconsin dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 37 samples in Oconomowoc. 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 10 contaminants in Oconomowoc, up to 249 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: 43 regulated sites located in Oconomowoc. 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.