Wisconsin Well Water Testing and Programs

Quick answer

About 1,517,000 people in Wisconsin (26.7% of residents) got their water from private wells in 2010, according to USGS estimates. Wisconsin Department of Natural Resources runs the state’s private well guidance. Wisconsin DHS's Well Testing Access Program (WellTAP) offers no-cost testing through local or Tribal health departments for primary-residence wells serving someone pregnant, a child 12 or under, or a person with a weakened immune system when a financial or other burden prevents testing.

People on private wells: 1,516,798
Share of residents: 26.7%
Rank among states: 8th
Well users modeled above 10 µg/L arsenic: 4.8%

Where to get your well tested in Wisconsin

Wisconsin Department of Natural Resources: Wells, the state’s guidance for private well owners.
Well water testing in Wisconsin: what to test for and how to collect a sample.
Certified laboratories in Wisconsin. Use a lab certified for drinking water, so results are reliable.

Free or low-cost testing

Wisconsin DHS's Well Testing Access Program (WellTAP) offers no-cost testing through local or Tribal health departments for primary-residence wells serving someone pregnant, a child 12 or under, or a person with a weakened immune system when a financial or other burden prevents testing. (source)

Mail-in lab kits are another option when no local lab is convenient. See well water test kits for what home kits can and can’t tell you.

What to test for

Every year: total coliform bacteria and nitrate.
Before buying equipment: pH, hardness, iron, manganese and, if there’s a smell, hydrogen sulfide.
Based on location: arsenic, uranium and radon, PFAS, and lead in older plumbing.

Private wells by county

Estimated people relying on private wells in each Wisconsin county in 2010, the share of residents that represents, and the modeled share of well users with arsenic above 10 µg/L. These are USGS model estimates (2010 population), not measurements of any well. Arsenic is hidden for counties with fewer than 500 well users.

County	People on wells	Share	Arsenic >10 µg/L
Waukesha County	107,264	27.5%	2.8%
Dane County	54,029	11.1%	4.1%
Marathon County	50,654	37.8%	5.8%
Racine County	37,617	19.3%	6.5%
Washington County	37,123	28.1%	2.6%
Walworth County	35,275	34.5%	7.3%
Outagamie County	34,425	19.5%	9.8%
St. Croix County	34,402	40.8%	2.1%
Rock County	33,666	21.0%	3.4%
Dodge County	31,845	35.9%	7.3%
Fond du Lac County	31,288	30.8%	3.5%
Winnebago County	30,437	18.2%	14.3%

Show all 72 counties

Chippewa County	29,913	47.9%	3.5%
Portage County	29,718	42.4%	4.3%
Kenosha County	29,390	17.7%	6.4%
Sheboygan County	28,345	24.5%	5.9%
Wood County	27,984	37.4%	5.3%
Waupaca County	27,817	53.1%	8.6%
Polk County	27,724	62.7%	3.6%
Brown County	27,489	11.1%	8.3%
Jefferson County	26,834	32.1%	7.7%
Ozaukee County	25,568	29.6%	4.1%
Oneida County	25,378	70.5%	2.5%
Oconto County	24,889	66.1%	4.1%
Sauk County	23,601	38.1%	5.0%
Barron County	23,555	51.4%	2.8%
Shawano County	23,233	55.4%	6.7%
Manitowoc County	23,060	28.3%	15.6%
Clark County	21,693	62.5%	4.1%
Columbia County	21,674	38.1%	4.5%
Marinette County	20,861	50.0%	1.8%
Monroe County	20,710	46.4%	3.2%
Dunn County	20,650	47.1%	2.9%
Eau Claire County	20,628	20.9%	2.5%
Milwaukee County	19,668	2.1%	3.8%
La Crosse County	18,576	16.2%	2.4%
Waushara County	18,531	75.7%	3.4%
Pierce County	17,993	43.9%	2.1%
Grant County	17,729	34.6%	3.7%
Vilas County	17,634	82.3%	2.7%
Adams County	16,343	78.3%	4.7%
Door County	16,226	58.4%	4.9%
Green County	15,997	43.4%	3.2%
Douglas County	15,526	35.2%	4.4%
Vernon County	15,363	51.6%	3.0%
Juneau County	15,172	56.9%	5.3%
Lincoln County	15,112	52.6%	3.3%
Taylor County	14,281	69.0%	3.9%
Trempealeau County	13,436	46.6%	3.0%
Kewaunee County	12,558	61.0%	14.7%
Burnett County	12,463	80.6%	2.7%
Marquette County	12,308	79.9%	9.1%
Sawyer County	11,997	72.5%	1.8%
Calumet County	11,544	23.6%	9.3%
Jackson County	11,227	54.9%	2.3%
Washburn County	11,146	70.1%	2.3%
Langlade County	10,990	55.0%	4.6%
Iowa County	9,995	42.2%	2.9%
Bayfield County	9,921	66.1%	2.4%
Green Lake County	9,789	51.4%	4.0%
Price County	9,510	67.2%	2.5%
Richland County	9,256	51.4%	3.0%
Rusk County	8,986	60.9%	2.1%
Buffalo County	8,689	64.0%	2.9%
Lafayette County	8,017	47.6%	3.9%
Crawford County	7,429	44.6%	3.6%
Forest County	6,368	68.4%	2.7%
Ashland County	5,337	33.0%	3.1%
Pepin County	4,523	60.6%	2.6%
Florence County	3,263	73.8%	2.5%
Iron County	2,834	47.9%	2.0%
Menominee County	2,322	54.9%	4.0%

Counties with the highest modeled arsenic share: Manitowoc County (15.6%), Kewaunee County (14.7%), Winnebago County (14.3%), Outagamie County (9.8%), Calumet County (9.3%).

After you get results

Enter your numbers in the test results tool to see what needs treating and in what order. The guide to reading a well water test explains units and limits.

Common questions

Does Wisconsin offer free well water testing?

Who oversees private wells in Wisconsin?

Wisconsin Department of Natural Resources (Wells) publishes guidance for private well owners. Private wells aren’t covered by the federal Safe Drinking Water Act, so testing and treatment are up to the owner.

How many people use private wells in Wisconsin?

USGS estimates about 1,517,000 people, or 26.7% of the population in 2010. That ranks 8th of the states covered by the estimate.

What should I test my well for in Wisconsin?

Test every year for total coliform bacteria and nitrate, plus pH, hardness, iron and manganese before buying equipment. Ask the state program or a certified lab about local concerns such as arsenic, uranium or PFAS.