Well Water Testing in Wisconsin: What to Test and When
Well water testing is the only way to know what is in a private well, and in Wisconsin it is up to the owner to do it [1][2]. Owners are not required to test on a schedule, but the Wisconsin Department of Natural Resources (DNR) and the Department of Health Services (DHS) recommend a short list of routine tests [2]. This guide covers what to test, how often, how to read the results, and what Wisconsin labs charge.
Who is responsible for a private well
A well is private if it has fewer than 15 connections and serves fewer than 25 people [3]. The state fact sheet puts it plainly: private well owners are responsible for testing and maintaining their wells, and it is their choice which tests to do [2].
Many problems give no warning. DHS says many substances that can affect health do not change the color, smell or taste of the water [4].
Private well testing: what Wisconsin recommends
The DNR and DHS fact sheet sets these routine tests [2]:
- Bacteria (total coliform and E. coli): once a year, and right away if the water's taste, color or smell changes [1][2].
- Nitrate: once a year, and before someone who is or may become pregnant uses the water or it is given to a baby [1][2].
- Arsenic: once every five years for most wells. Test every year if you live in Outagamie, Winnebago or Brown county or a past sample showed arsenic [1][2].
- Lead: once every five years, and before a pregnant person uses the water or it is given to a baby [2].
Other tests depend on where you live and how the land around the well is used [2]:
- Fluoride: test at least once.
- Manganese: test if the water is brown or black or stains faucets or laundry.
- Strontium: test if you live in the eastern or northern part of the state.
- Atrazine: test if you live near areas where pesticides are used, made or stored.
- VOCs: test if you live near a landfill, gas station or dry cleaner.
- PFAS: consider testing if you live near a known PFAS site.
How to take a good sample
Use a lab certified in Wisconsin. The fact sheet says certified labs may include your local health department, a University of Wisconsin lab or a commercial lab [2]. The DNR posts lists of certified drinking water labs, and bacteria labs are certified through the Department of Agriculture, Trade and Consumer Protection (DATCP) [5].
The lab sends a sampling kit, and you need to follow its directions [1]. The DNR says owners often get false positives because they collect the sample wrong or do not get it to the lab within the 48 hours needed for an accurate test [1]. Plan around lab hours. UW-Stevens Point, for example, does not accept bacteria samples on Fridays [6].
Reading your results
Bacteria present. Stop drinking the water [1]. DHS says to use another source, such as water boiled for one minute or bottled water, for drinking, rinsing produce, brushing teeth and bathing babies, and to collect a second sample to confirm [7]. If bacteria are still present, work with a licensed well professional to disinfect the well and retest a week later [7].
Nitrate at 10 mg/L or more. People who are or may become pregnant should use a different water source for drinking and for foods that take up a lot of water, and babies should get water from another source [8]. The water can still be used for bathing and washing dishes [8]. Retest to confirm, and if it is still high, look at a certified treatment device or a new well [8].
Arsenic at 10 micrograms per liter or more. Use another source for drinking, baby formula and foods that take up a lot of water, and confirm with a second sample [9]. Long-term fixes are a certified treatment device or a new well [9].
What testing costs at Wisconsin labs
These are the posted prices of the Wisconsin State Laboratory of Hygiene (WSLH) and UW-Stevens Point, not quotes from contractors.
| Test | Lab | Price |
|---|---|---|
| Bacteria (total coliform and E. coli) | WSLH | $35 [10] |
| Nitrate | WSLH | $35 [10] |
| Arsenic | WSLH | $38 [10] |
| Homeowner Package (bacteria, nitrate, metals, VOC and atrazine screens and more) | WSLH | $450 [10] |
| HUD/FHA-VA Loan Package | WSLH | $146 [10] |
| Homeowner Package (bacteria, nitrate, pH, hardness and more) | UW-Stevens Point (checked Nov 2026) | $78 [6] |
| Standard Metals Package | UW-Stevens Point (checked Nov 2026) | $75 [6] |
| Comprehensive Homeowner Package | UW-Stevens Point (checked Nov 2026) | $191 [6] |
The WSLH prices took effect July 1, 2026 and can change without notice [10]. Some households can test for free. Through WellTAP, a well serving someone who is pregnant, a child 12 or under, or a person with a weakened immune system may qualify for no-cost testing through the local or Tribal health department, if it is the primary residence and cost is a burden [4]. For well drilling and pump prices, see our well and septic cost guide.
Testing when you buy or sell a home
Wisconsin does not require a well inspection when property changes hands [11]. If one is done for pay, only a licensed water well driller or licensed pump installer, or in some counties a trained county inspector, may do it, and the inspector must sample each drinking water well for total coliform bacteria, nitrate and arsenic [11]. Anyone may collect a sample if the only result is a certified lab report with no opinions about the well [11]. The DNR keeps a directory of licensed pros who offer these inspections [12]. To confirm a license, see our guide on how to check a well or septic contractor's license.
Help if your well is contaminated
The DNR's well compensation grant can help replace, reconstruct or treat a contaminated well serving a home [13]. Family income may not exceed $65,000 for the prior year, the program pays 75% of eligible costs, and the maximum grant is $12,000 [13]. Bacteria and nitrate are excluded from the chemical category. Arsenic qualifies at 50 micrograms per liter or more, nitrate at 40 parts per million nitrate-nitrogen or more when the well serves both livestock and the home, and some livestock fecal bacteria cases qualify too [13]. Work done before DNR approval is not reimbursed [13].
Well water testing FAQ
How often should I test my well in Wisconsin?
Test for bacteria and nitrate once a year, arsenic every five years for most wells, and lead every five years [2]. Test for bacteria right away if taste, color or smell changes [1].
Is well testing required by law?
Not for homeowners. The state fact sheet says owners are not required to regularly test [2]. A paid inspection at a sale must include bacteria, nitrate and arsenic samples [11].
My test showed coliform bacteria. Now what?
Stop drinking the water, use another source, and retest to confirm [1][7]. If it is still positive, have a licensed well professional disinfect the well and retest a week later [7].
Get quotes for well water testing
If you want a licensed well professional to sample your water, inspect the well before a sale, or disinfect a well that tested positive, send one request through our free Get quotes form to reach well companies in your area. We're a referral service, not a contractor. We pass your request to independent local contractors who may contact you.
Contractors who get your request may pay us a referral fee. We don't check licenses, and a listing here is not an endorsement.
Sources
- Wisconsin DNR, Test Your Private Well Water Annually, https://dnr.wisconsin.gov/topic/Wells/privateWellTest.html (fetched Nov 10, 2026). Bacteria, nitrate and arsenic schedule; 48-hour sample rule and false positives; follow the lab kit; stop drinking if bacteria present.
- Wisconsin DNR and DHS, Tests for Private Well Users, PUB-DG-023-2026, https://dnr.wisconsin.gov/sites/default/files/topic/DrinkingWater/Publications/DG023.pdf (fetched Nov 10, 2026). Owner responsibility and no required testing; annual, five-year and situational tests; certified lab types.
- Wisconsin DNR, Information for Private Well Owners, https://dnr.wisconsin.gov/topic/Wells/homeowners.html (fetched Nov 10, 2026). Private well definition; owner responsibility.
- Wisconsin DHS, Drinking Water: Private Wells, https://www.dhs.wisconsin.gov/water/private.htm (fetched Nov 10, 2026). Many substances do not change color, smell or taste; WellTAP eligibility.
- Wisconsin DNR, Laboratories (certified lab lists, September 2026), https://dnr.wisconsin.gov/topic/labCert/certified-lab-lists (fetched Nov 10, 2026). Certified drinking water lab lists; DATCP certified labs for total coliform and E. coli.
- UW-Stevens Point Center for Watershed Science and Education, Well Water Testing, https://www.uwsp.edu/center-for-watershed-science-and-education/well-water-testing/ (posted prices, checked Nov 2026; fetched Nov 11, 2026). Homeowner Package $78; Standard Metals $75; Comprehensive $191; no bacteria samples on Fridays.
- Wisconsin DHS, Bacteria in Private Well Water, P-02132 (09/2023), https://www.dhs.wisconsin.gov/publications/p02132.pdf (fetched Nov 10, 2026). Steps when bacteria are present; disinfect with a licensed well professional; retest a week later.
- Wisconsin DHS, Nitrate in Private Well Water, P-02128 (09/2023), https://www.dhs.wisconsin.gov/publications/p02128.pdf (fetched Nov 10, 2026). Action at 10 mg/L; who should switch water; long-term fixes.
- Wisconsin DHS, Arsenic in Private Well Water, P-45012 (09/2023), https://www.dhs.wisconsin.gov/publications/p4/p45012.pdf (fetched Nov 10, 2026). Action at 10 micrograms per liter; steps and long-term fixes.
- Wisconsin State Laboratory of Hygiene, Public Environmental and Water Testing Prices (effective July 1, 2026), https://www.slh.wisc.edu/environmental/water/public-environmental-and-water-testing-prices/ (fetched Nov 10, 2026). Bacteria $35; nitrate $35; arsenic $38; Homeowner Package $450; HUD/FHA-VA $146.
- Wis. Admin. Code ch. NR 812 (NR 812.44, 812.46), https://docs.legis.wisconsin.gov/document/administrativecode/ch.%20NR%20812.pdf (fetched Nov 10, 2026). Inspection not required at transfer; only licensed drillers or pump installers for pay, or Level 3 county employees (812.44(1)(d)); bacteria, nitrate and arsenic samples; sample-only exception.
- Wisconsin DNR, Drilling and Pump Installing Service Directories, https://dnr.wisconsin.gov/topic/Wells/contacts.html (fetched Nov 10, 2026). Property transfer well inspection services directory.
- Wisconsin DNR, Well Compensation Grant Program, https://dnr.wisconsin.gov/aid/WellCompensation.html (fetched Nov 10, 2026). Purpose; $65,000 income limit; 75% of eligible costs; $12,000 maximum; exclusions; arsenic 50 ug/l, nitrate 40 ppm with livestock, livestock fecal bacteria; no pre-approval work.