Quick answer
About 1,822,000 people in Ohio (15.8% of residents) got their water from private wells in 2010, according to USGS estimates. Ohio Department of Health runs the state’s private well guidance. We didn’t find a free statewide well testing program in Ohio. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
- People on private wells
- 1,821,733
- Share of residents
- 15.8%
- Rank among states
- 6th
- Well users modeled above 10 µg/L arsenic
- 11.1%
Where to get your well tested in Ohio
- Ohio Department of Health: Private Water Systems Program, the state’s guidance for private well owners.
Free or low-cost testing
We didn’t find a free statewide program in Ohio. Certified labs charge per test; county health departments sometimes offer lower-cost bacteria and nitrate tests.
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 11.1% of Ohio’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 Ohio 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 |
|---|---|---|---|
| Stark County | 100,593 | 26.8% | 6.7% |
| Summit County | 87,214 | 16.1% | 5.7% |
| Trumbull County | 57,721 | 27.4% | 25.3% |
| Geauga County | 56,566 | 60.6% | 8.1% |
| Portage County | 52,271 | 32.4% | 11.0% |
| Licking County | 50,781 | 30.5% | 13.6% |
| Wayne County | 47,333 | 41.3% | 9.7% |
| Columbiana County | 42,929 | 39.8% | 4.9% |
| Richland County | 41,736 | 33.5% | 19.4% |
| Fairfield County | 40,538 | 27.7% | 13.2% |
| Clark County | 38,032 | 27.5% | 14.7% |
| Franklin County | 33,390 | 2.9% | 9.2% |
Show all 88 counties
| Ashtabula County | 33,053 | 32.6% | 28.7% |
| Mahoning County | 31,250 | 13.1% | 10.5% |
| Allen County | 30,055 | 28.3% | 10.2% |
| Montgomery County | 29,452 | 5.5% | 18.3% |
| Wood County | 29,429 | 23.5% | 4.1% |
| Miami County | 28,110 | 27.4% | 26.9% |
| Greene County | 27,465 | 17.0% | 17.1% |
| Darke County | 27,049 | 51.1% | 57.0% |
| Tuscarawas County | 26,110 | 28.2% | 2.8% |
| Holmes County | 25,638 | 60.5% | 3.6% |
| Knox County | 25,450 | 41.8% | 7.4% |
| Morrow County | 24,777 | 71.1% | 16.0% |
| Lucas County | 24,521 | 5.6% | 4.7% |
| Pickaway County | 23,231 | 41.7% | 9.8% |
| Sandusky County | 22,520 | 37.0% | 12.3% |
| Seneca County | 21,886 | 38.6% | 11.0% |
| Medina County | 21,866 | 12.7% | 15.2% |
| Muskingum County | 21,835 | 25.4% | 1.8% |
| Union County | 21,728 | 41.5% | 3.4% |
| Logan County | 21,355 | 46.6% | 13.0% |
| Shelby County | 19,351 | 39.2% | 36.1% |
| Champaign County | 19,280 | 48.1% | 16.9% |
| Ross County | 19,194 | 24.6% | 4.2% |
| Marion County | 19,009 | 28.6% | 3.7% |
| Hancock County | 18,956 | 25.3% | 4.6% |
| Butler County | 18,826 | 5.1% | 6.0% |
| Putnam County | 17,615 | 51.1% | 1.9% |
| Ashland County | 17,546 | 33.0% | 13.7% |
| Madison County | 17,475 | 40.2% | 7.4% |
| Preble County | 17,326 | 41.0% | 21.1% |
| Fulton County | 16,508 | 38.7% | 16.6% |
| Auglaize County | 16,445 | 35.8% | 8.2% |
| Mercer County | 16,409 | 40.2% | 12.1% |
| Carroll County | 15,967 | 55.4% | 3.0% |
| Williams County | 15,742 | 41.8% | 15.1% |
| Huron County | 15,706 | 26.3% | 15.2% |
| Coshocton County | 15,590 | 42.2% | 2.1% |
| Warren County | 15,364 | 7.2% | 9.2% |
| Hocking County | 14,700 | 50.0% | 2.8% |
| Ottawa County | 14,591 | 35.2% | 11.4% |
| Jefferson County | 13,992 | 20.1% | 3.0% |
| Delaware County | 13,584 | 7.8% | 9.3% |
| Perry County | 13,569 | 37.6% | 3.7% |
| Lake County | 13,464 | 5.9% | 11.1% |
| Crawford County | 12,786 | 29.2% | 22.3% |
| Hardin County | 12,692 | 39.6% | 3.3% |
| Washington County | 12,108 | 19.6% | 2.2% |
| Cuyahoga County | 12,056 | 0.9% | 6.5% |
| Van Wert County | 11,606 | 40.4% | 2.9% |
| Lawrence County | 11,394 | 18.2% | 3.3% |
| Defiance County | 11,313 | 29.0% | 2.4% |
| Henry County | 11,132 | 39.5% | 2.3% |
| Paulding County | 10,909 | 55.6% | 1.8% |
| Clinton County | 10,757 | 25.6% | 21.9% |
| Highland County | 10,497 | 24.1% | 15.4% |
| Fayette County | 10,496 | 36.2% | 19.1% |
| Guernsey County | 10,223 | 25.5% | 1.7% |
| Wyandot County | 9,574 | 42.3% | 6.5% |
| Erie County | 8,287 | 10.8% | 8.8% |
| Belmont County | 8,213 | 11.7% | 2.3% |
| Vinton County | 7,591 | 56.5% | 2.8% |
| Lorain County | 7,442 | 2.5% | 9.9% |
| Pike County | 6,951 | 24.2% | 2.2% |
| Jackson County | 6,562 | 19.7% | 2.4% |
| Hamilton County | 6,053 | 0.8% | 4.6% |
| Morgan County | 5,800 | 38.5% | 2.1% |
| Athens County | 5,753 | 8.9% | 2.3% |
| Harrison County | 5,667 | 35.7% | 2.0% |
| Scioto County | 5,398 | 6.8% | 2.9% |
| Meigs County | 5,049 | 21.2% | 3.2% |
| Adams County | 4,958 | 17.4% | 4.2% |
| Monroe County | 4,636 | 31.7% | 2.4% |
| Clermont County | 3,723 | 1.9% | 6.5% |
| Gallia County | 3,705 | 12.0% | 3.0% |
| Noble County | 3,361 | 23.0% | 2.0% |
| Brown County | 2,948 | 6.6% | 8.3% |
Counties with the highest modeled arsenic share: Darke County (57.0%), Shelby County (36.1%), Ashtabula County (28.7%), Miami County (26.9%), Trumbull County (25.3%).
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 Ohio offer free well water testing?
We didn’t find a free statewide well testing program in Ohio. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
Who oversees private wells in Ohio?
Ohio Department of Health (Private Water Systems 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 Ohio?
USGS estimates about 1,822,000 people, or 15.8% of the population in 2010. That ranks 6th of the states covered by the estimate.
What should I test my well for in Ohio?
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 Ohio, so add it to the first test.