Well water in Oasis, Wisconsin
In Oasis, chloride was detected in 96% of 84 tested well samples from USGS Water Quality Portal.
The strongest signal is nitrate: 29% of 52 local wells tested were above the Wisconsin enforcement standard, too few samples to carry the headline but first on the test list below.
52 private wells tested 1988 to 2025 in state summaries; 320 test results across 8 contaminants from at least 23 wells, 1954 to 2019; chloride has the most at 84. 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, 1988 to 2025. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.
What individual samples found
Each row summarizes every public sample for that contaminant inside Oasis. 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 | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Chloride 1954 to 2019 | no limit | 84 | 96% | 2.33 | 61.5 | 250 mg/L nuisance level |
| Sodium 1973 to 2019 | no limit | 82 | 98% | 2.85 | 254 | 20 mg/L health guideline |
| Iron 1954 to 2019 | no limit | 72 | 79% | 280 | 386,000 | 300 ug/L nuisance level |
| Manganese 1954 to 2019 | no limit | 71 | 92% | 17.7 | 11,100 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Nitrate (3), Fluoride (4), Lead (2), Arsenic (2).
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 Oasis who sent a sample to the state lab, the health-based limits most often exceeded were nitrate (29% of 52 wells) and total coliform (6% of 16 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 Oasis
- 1Nitrate29% of 52 local wells tested were above the Wisconsin enforcement standard.
- 2Total coliform6% of 16 local wells tested were above the Wisconsin limit (any detection).
- 3Coliform bacteriaRecommended for every private well, every year.
- 4ChlorideDetected in 96% of local samples.
- 5ManganeseDetected in 92% of local samples.
- 6IronDetected in 79% of local samples.
- 7FluorideDetected in 75% of local samples.
Test your Oasis well for nitrate, total coliform and coliform bacteria
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.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
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 Oasis numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Oasis
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
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Total coliform
Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
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 nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For total coliform
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.
For iron
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 Oasis
No water treatment company serves Oasis 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 Oasis, and you get an email naming it first.
Common questions
How often should I test a private well in Oasis?
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 Oasis
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: 320 samples in Oasis. 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 Oasis, up to 52 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.
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.