Quick answer
About 470,000 people in Oklahoma (12.5% of residents) got their water from private wells in 2010, according to USGS estimates. Oklahoma Department of Environmental Quality runs the state’s private well guidance. We didn’t find a free statewide well testing program in Oklahoma. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
- People on private wells
- 470,032
- Share of residents
- 12.5%
- Rank among states
- 28th
- Well users modeled above 10 µg/L arsenic
- 3.6%
Where to get your well tested in Oklahoma
- Oklahoma Department of Environmental Quality: State Environmental Laboratory Services, the state’s guidance for private well owners.
- Well water testing in Oklahoma: what to test for and how to collect a sample.
- Certified laboratories in Oklahoma. Use a lab certified for drinking water, so results are reliable.
Free or low-cost testing
We didn’t find a free statewide program in Oklahoma. 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.
Private wells by county
Estimated people relying on private wells in each Oklahoma 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 |
|---|---|---|---|
| Oklahoma County | 52,239 | 7.3% | 3.2% |
| Cleveland County | 33,101 | 12.9% | 3.2% |
| Pottawatomie County | 25,033 | 36.0% | 3.7% |
| Grady County | 18,997 | 36.2% | 2.7% |
| Lincoln County | 18,870 | 55.1% | 5.3% |
| Delaware County | 18,391 | 44.3% | 1.0% |
| McClain County | 13,659 | 39.6% | 3.1% |
| Creek County | 13,298 | 19.0% | 8.1% |
| Logan County | 12,612 | 30.1% | 3.2% |
| Cherokee County | 12,547 | 26.7% | 1.2% |
| Canadian County | 11,614 | 10.1% | 3.6% |
| McCurtain County | 10,687 | 32.2% | 1.5% |
Show all 77 counties
| Adair County | 10,416 | 45.9% | 1.0% |
| Caddo County | 10,000 | 33.8% | 3.3% |
| Payne County | 8,966 | 11.6% | 7.2% |
| Stephens County | 8,706 | 19.3% | 3.1% |
| Garfield County | 8,530 | 14.1% | 4.3% |
| Bryan County | 8,365 | 19.7% | 2.0% |
| Seminole County | 7,917 | 31.1% | 5.9% |
| Sequoyah County | 7,389 | 17.4% | 2.4% |
| Mayes County | 7,255 | 17.6% | 1.4% |
| Carter County | 7,215 | 15.2% | 3.5% |
| Le Flore County | 6,350 | 12.6% | 2.3% |
| Comanche County | 6,010 | 4.8% | 5.9% |
| Choctaw County | 5,886 | 38.7% | 2.3% |
| Garvin County | 5,834 | 21.2% | 3.0% |
| Osage County | 5,759 | 12.1% | 7.2% |
| Ottawa County | 5,678 | 17.8% | 1.6% |
| Tulsa County | 4,589 | 0.8% | 7.2% |
| Pontotoc County | 4,330 | 11.5% | 6.0% |
| Haskell County | 4,240 | 33.2% | 3.7% |
| Atoka County | 4,003 | 28.2% | 2.4% |
| Pawnee County | 3,957 | 23.9% | 6.1% |
| Pushmataha County | 3,790 | 32.7% | 1.8% |
| Beckham County | 3,686 | 16.7% | 3.4% |
| Woodward County | 3,644 | 18.1% | 3.1% |
| Wagoner County | 3,563 | 4.9% | 5.0% |
| McIntosh County | 3,519 | 17.4% | 4.2% |
| Muskogee County | 3,475 | 4.9% | 3.8% |
| Kay County | 3,403 | 7.3% | 8.3% |
| Custer County | 3,272 | 11.9% | 3.1% |
| Kingfisher County | 3,203 | 21.3% | 5.8% |
| Pittsburg County | 3,155 | 6.9% | 4.8% |
| Rogers County | 3,030 | 3.5% | 7.3% |
| Major County | 3,001 | 39.9% | 4.0% |
| Hughes County | 2,961 | 21.1% | 6.2% |
| Texas County | 2,948 | 14.3% | 5.4% |
| Beaver County | 2,678 | 47.5% | 3.5% |
| Okfuskee County | 2,674 | 21.9% | 7.5% |
| Blaine County | 2,523 | 21.1% | 4.0% |
| Marshall County | 2,521 | 15.9% | 2.5% |
| Love County | 2,460 | 26.1% | 2.4% |
| Johnston County | 2,380 | 21.7% | 2.0% |
| Washita County | 2,156 | 18.5% | 3.9% |
| Craig County | 1,727 | 11.5% | 3.0% |
| Jackson County | 1,590 | 6.0% | 3.0% |
| Murray County | 1,587 | 11.8% | 3.1% |
| Okmulgee County | 1,546 | 3.9% | 4.8% |
| Noble County | 1,513 | 13.1% | 4.3% |
| Roger Mills County | 1,398 | 38.3% | 3.0% |
| Dewey County | 1,304 | 27.1% | 3.0% |
| Ellis County | 1,297 | 31.2% | 3.0% |
| Harmon County | 1,201 | 41.1% | 3.0% |
| Alfalfa County | 907 | 16.1% | 4.4% |
| Jefferson County | 847 | 13.1% | 4.6% |
| Washington County | 845 | 1.7% | 4.5% |
| Latimer County | 809 | 7.3% | 1.4% |
| Woods County | 798 | 9.0% | 3.0% |
| Cotton County | 780 | 12.6% | 6.8% |
| Coal County | 765 | 12.9% | 5.2% |
| Cimarron County | 712 | 28.8% | 10.0% |
| Nowata County | 705 | 6.7% | 3.7% |
| Kiowa County | 676 | 7.2% | 3.5% |
| Tillman County | 668 | 8.4% | 4.2% |
| Harper County | 644 | 17.5% | 2.8% |
| Grant County | 624 | 13.8% | 6.0% |
| Greer County | 604 | 9.7% | 3.0% |
Counties with the highest modeled arsenic share: Cimarron County (10.0%), Kay County (8.3%), Creek County (8.1%), Okfuskee County (7.5%), Rogers County (7.3%).
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 Oklahoma offer free well water testing?
We didn’t find a free statewide well testing program in Oklahoma. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
Who oversees private wells in Oklahoma?
Oklahoma Department of Environmental Quality (State Environmental Laboratory Services) 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 Oklahoma?
USGS estimates about 470,000 people, or 12.5% of the population in 2010. That ranks 28th of the states covered by the estimate.
What should I test my well for in Oklahoma?
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.
Sources
- Oklahoma Department of Environmental Quality: State Environmental Laboratory Services
- Oklahoma Department of Environmental Quality: well water testing
- Oklahoma certified laboratories
- 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)