Quick answer
About 502,000 people in Iowa (16.5% of residents) got their water from private wells in 2010, according to USGS estimates. Iowa Department of Natural Resources runs the state’s private well guidance. Iowa's Private Well Grants program (run by Iowa HHS through county environmental health offices) gives all private well owners and users free testing for bacteria and nitrate every year and for arsenic and manganese every 3 years.
- People on private wells
- 501,833
- Share of residents
- 16.5%
- Rank among states
- 26th
- Well users modeled above 10 µg/L arsenic
- 11.7%
Where to get your well tested in Iowa
- Iowa Department of Natural Resources: Private Well Program, the state’s guidance for private well owners.
- Well water testing in Iowa: what to test for and how to collect a sample.
- Certified laboratories in Iowa. Use a lab certified for drinking water, so results are reliable.
Free or low-cost testing
Iowa's Private Well Grants program (run by Iowa HHS through county environmental health offices) gives all private well owners and users free testing for bacteria and nitrate every year and for arsenic and manganese every 3 years. (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.
USGS modeling estimates that about 11.7% of Iowa’s private well users have water above the 10 µg/L arsenic limit. Arsenic has no taste or smell, so include it in your first test.
Private wells by county
Estimated people relying on private wells in each Iowa 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 |
|---|---|---|---|
| Linn County | 24,033 | 11.4% | 5.1% |
| Dubuque County | 20,012 | 21.4% | 5.6% |
| Johnson County | 16,314 | 12.5% | 11.1% |
| Pottawattamie County | 15,894 | 17.1% | 10.0% |
| Black Hawk County | 12,882 | 9.8% | 4.5% |
| Scott County | 11,206 | 6.8% | 15.0% |
| Warren County | 10,705 | 23.2% | 16.5% |
| Clinton County | 10,623 | 21.6% | 11.2% |
| Muscatine County | 10,104 | 23.6% | 8.5% |
| Polk County | 9,963 | 2.3% | 23.6% |
| Benton County | 8,744 | 33.5% | 8.4% |
| Delaware County | 8,546 | 48.1% | 8.2% |
Show all 99 counties
| Clayton County | 8,246 | 45.5% | 7.4% |
| Buchanan County | 8,244 | 39.3% | 5.0% |
| Lee County | 8,104 | 22.6% | 10.0% |
| Winneshiek County | 8,070 | 38.3% | 4.3% |
| Jones County | 8,021 | 38.9% | 9.6% |
| Dallas County | 7,960 | 12.0% | 21.3% |
| Woodbury County | 7,930 | 7.8% | 22.5% |
| Des Moines County | 7,480 | 18.5% | 9.1% |
| Jackson County | 7,470 | 37.6% | 7.4% |
| Bremer County | 7,393 | 30.5% | 6.1% |
| Story County | 7,359 | 8.2% | 34.7% |
| Washington County | 7,009 | 32.3% | 10.0% |
| Plymouth County | 6,860 | 27.5% | 12.0% |
| Madison County | 6,842 | 43.6% | 8.0% |
| Fayette County | 6,757 | 32.4% | 2.4% |
| Allamakee County | 6,511 | 45.4% | 5.5% |
| Cedar County | 6,371 | 34.4% | 10.6% |
| Webster County | 6,003 | 15.8% | 11.4% |
| Butler County | 5,886 | 39.6% | 4.3% |
| Cerro Gordo County | 5,636 | 12.8% | 6.1% |
| Harrison County | 5,575 | 37.3% | 8.8% |
| Mills County | 5,425 | 36.0% | 6.6% |
| Iowa County | 5,235 | 32.0% | 13.3% |
| Boone County | 5,213 | 19.8% | 11.1% |
| Kossuth County | 5,132 | 33.0% | 31.9% |
| Tama County | 5,066 | 28.5% | 10.5% |
| Henry County | 4,983 | 24.7% | 9.9% |
| Chickasaw County | 4,926 | 39.6% | 8.2% |
| Mitchell County | 4,847 | 45.0% | 4.5% |
| Louisa County | 4,786 | 42.0% | 6.3% |
| Floyd County | 4,781 | 29.3% | 5.0% |
| Hardin County | 4,475 | 25.5% | 11.7% |
| Jasper County | 4,387 | 11.9% | 16.3% |
| Grundy County | 4,213 | 33.8% | 15.5% |
| Marion County | 3,972 | 11.9% | 12.4% |
| Keokuk County | 3,966 | 37.7% | 11.4% |
| Franklin County | 3,910 | 36.6% | 25.6% |
| Marshall County | 3,639 | 9.0% | 23.1% |
| Hamilton County | 3,600 | 23.0% | 11.8% |
| Buena Vista County | 3,581 | 17.7% | 36.3% |
| Hancock County | 3,483 | 30.7% | 11.2% |
| Crawford County | 3,475 | 20.3% | 4.2% |
| Jefferson County | 3,463 | 20.6% | 13.0% |
| Howard County | 3,425 | 35.8% | 6.4% |
| Sioux County | 3,336 | 9.9% | 26.4% |
| Guthrie County | 3,272 | 29.9% | 8.0% |
| Winnebago County | 3,129 | 28.8% | 16.1% |
| Carroll County | 3,101 | 14.9% | 9.8% |
| Worth County | 3,051 | 40.2% | 6.4% |
| Shelby County | 3,045 | 25.0% | 4.6% |
| Sac County | 3,009 | 29.1% | 27.1% |
| Monona County | 2,998 | 32.4% | 12.0% |
| Clarke County | 2,813 | 30.3% | 12.2% |
| Cass County | 2,803 | 20.1% | 8.2% |
| Mahaska County | 2,765 | 12.4% | 7.4% |
| Dickinson County | 2,762 | 16.6% | 33.8% |
| Wright County | 2,659 | 20.1% | 11.0% |
| Wapello County | 2,620 | 7.4% | 13.0% |
| Greene County | 2,493 | 26.7% | 8.6% |
| Adair County | 2,353 | 30.6% | 6.1% |
| Palo Alto County | 2,317 | 24.6% | 33.8% |
| Lyon County | 2,315 | 20.0% | 38.2% |
| Humboldt County | 2,256 | 23.0% | 13.2% |
| Fremont County | 2,230 | 30.0% | 8.9% |
| Montgomery County | 2,219 | 20.7% | 6.7% |
| Pocahontas County | 2,208 | 30.2% | 16.9% |
| Poweshiek County | 2,179 | 11.5% | 16.9% |
| Ida County | 2,164 | 30.5% | 8.2% |
| Calhoun County | 2,151 | 22.2% | 15.9% |
| Audubon County | 2,134 | 34.9% | 9.4% |
| Emmet County | 1,922 | 18.7% | 32.9% |
| Cherokee County | 1,895 | 15.7% | 30.0% |
| Union County | 1,884 | 15.0% | 6.4% |
| Decatur County | 1,882 | 22.3% | 7.0% |
| Taylor County | 1,836 | 29.1% | 4.2% |
| Ringgold County | 1,718 | 33.5% | 5.5% |
| Page County | 1,704 | 10.7% | 5.8% |
| Adams County | 1,664 | 41.3% | 6.8% |
| O'Brien County | 1,518 | 10.5% | 33.2% |
| Osceola County | 1,509 | 23.4% | 32.8% |
| Clay County | 1,402 | 8.4% | 61.5% |
| Davis County | 1,206 | 13.8% | 7.0% |
| Van Buren County | 1,162 | 15.4% | 7.5% |
| Appanoose County | 1,003 | 7.8% | 9.3% |
| Lucas County | 985 | 11.1% | 10.0% |
| Wayne County | 849 | 13.3% | 14.1% |
| Monroe County | 576 | 7.2% | 6.7% |
Counties with the highest modeled arsenic share: Clay County (61.5%), Lyon County (38.2%), Buena Vista County (36.3%), Story County (34.7%), Dickinson County (33.8%).
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 Iowa offer free well water testing?
Iowa's Private Well Grants program (run by Iowa HHS through county environmental health offices) gives all private well owners and users free testing for bacteria and nitrate every year and for arsenic and manganese every 3 years.
Who oversees private wells in Iowa?
Iowa Department of Natural Resources (Private Well Program) 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 Iowa?
USGS estimates about 502,000 people, or 16.5% of the population in 2010. That ranks 26th of the states covered by the estimate.
What should I test my well for in Iowa?
Test every year for total coliform bacteria and nitrate, plus pH, hardness, iron and manganese before buying equipment. Arsenic is a known concern in parts of Iowa, so add it to the first test.
Sources
- Iowa Department of Natural Resources: Private Well Program
- Iowa Department of Natural Resources: well water testing
- Iowa certified laboratories
- Iowa free or low-cost testing
- USGS data release: domestic well locations and populations served, 2000 and 2010 (Johnson, Belitz and Lombard, 2019)
- CDC Environmental Public Health Tracking: private well water data (from USGS)