Private wells
Oklahoma well water: who's on a well and what to test for
People on private wells
811,300
Homes on wells
20.3%
Est. above arsenic limit
4,300
Every Oklahoma county
Sorted by people on private wells. Arsenic and nitrate are modeled for typical wells in the county, not measured at yours; depth is the median of domestic well records.
| Oklahoma County | 80,200 | 9% | 3.1% | 2.3 | 180 ft |
| Cleveland County | 44,900 | 15% | 3.3% | 1.3 | 180 ft |
| Pottawatomie County | 29,600 | 40% | 3.6% | 1.6 | 160 ft |
| Grady County | 25,000 | 44% | 2.9% | 4.3 | 150 ft |
| Logan County | 24,800 | 50% | 3.0% | 2.7 | 180 ft |
| Garfield County | 22,700 | 37% | 4.4% | 10.2 | 49 ft |
| Creek County | 22,200 | 31% | 8.1% | 0.4 | 164 ft |
| Canadian County | 21,600 | 14% | 3.6% | 7.3 | 120 ft |
| Delaware County | 21,300 | 50% | 1.2% | 0.3 | 300 ft |
| Tulsa County | 20,000 | 3% | 7.1% | 1.7 | 80 ft |
| Lincoln County | 19,800 | 56% | 5.3% | 1.4 | 167 ft |
| Rogers County | 19,100 | 20% | 7.2% | 1.1 | 103 ft |
| Cherokee County | 18,600 | 38% | 1.3% | 0.3 | 200 ft |
| McClain County | 18,400 | 43% | 2.9% | 3.4 | 140 ft |
| Le Flore County | 16,100 | 34% | 2.2% | 0.1 | 160 ft |
| Payne County | 15,900 | 19% | 7.3% | 2.7 | 148 ft |
| Mayes County | 15,600 | 39% | 1.6% | 0.4 | 163 ft |
| McCurtain County | 14,800 | 49% | 1.6% | 0.2 | 144 ft |
| Carter County | 14,500 | 30% | 3.3% | 1.2 | 140 ft |
| Osage County | 14,300 | 32% | 7.1% | 0.8 | 150 ft |
| Bryan County | 14,300 | 31% | 2.1% | 0.5 | 133 ft |
| Sequoyah County | 13,400 | 34% | 2.4% | 0.2 | 180 ft |
| Stephens County | 13,300 | 30% | 3.0% | 3.2 | 140 ft |
| Wagoner County | 13,000 | 17% | 5.1% | 1.0 | 85 ft |
| Muskogee County | 12,500 | 19% | 3.5% | 0.3 | 130 ft |
| Comanche County | 12,300 | 9% | 5.9% | 3.3 | 120 ft |
| Pittsburg County | 12,000 | 28% | 4.6% | 0.2 | 120 ft |
| Adair County | 11,100 | 56% | 1.2% | 0.4 | 200 ft |
| Okmulgee County | 11,000 | 29% | 4.9% | 0.5 | 170 ft |
| Pontotoc County | 11,000 | 27% | 6.0% | 0.6 | 160 ft |
| Seminole County | 10,500 | 44% | 5.9% | 0.5 | 190 ft |
| Garvin County | 9,800 | 36% | 3.1% | 2.7 | 110 ft |
| Caddo County | 9,500 | 41% | 3.4% | 8.5 | 120 ft |
| Ottawa County | 9,100 | 30% | 1.9% | 0.1 | 365 ft |
| McIntosh County | 8,600 | 42% | 4.3% | 0.3 | 118 ft |
| Atoka County | 7,800 | 61% | 2.4% | 0.5 | 122 ft |
| Pawnee County | 7,200 | 45% | 6.2% | 0.8 | 160 ft |
| Washington County | 6,900 | 12% | 4.5% | 1.0 | n/a |
| Choctaw County | 6,500 | 45% | 2.2% | 0.3 | 120 ft |
| Kay County | 6,400 | 14% | 8.0% | 6.6 | 38 ft |
| Pushmataha County | 6,200 | 56% | 1.6% | 0.2 | 160 ft |
| Haskell County | 6,100 | 52% | 3.8% | 0.1 | 145 ft |
| Okfuskee County | 5,900 | 48% | 7.6% | 0.9 | 160 ft |
| Woodward County | 5,800 | 22% | 3.4% | 10.2 | 80 ft |
| Craig County | 5,800 | 39% | 3.0% | 0.5 | 192 ft |
| Custer County | 5,600 | 18% | 3.3% | 6.3 | 160 ft |
| Marshall County | 5,400 | 39% | 2.3% | 0.8 | 151 ft |
| Kingfisher County | 5,400 | 35% | 6.1% | 17.8 | 67 ft |
| Hughes County | 4,900 | 44% | 6.1% | 0.7 | 157 ft |
| Beckham County | 4,800 | 20% | 3.6% | 7.7 | 100 ft |
| Love County | 4,600 | 46% | 2.6% | 2.7 | 125 ft |
| Johnston County | 4,500 | 46% | 2.2% | 0.7 | 160 ft |
| Latimer County | 4,000 | 43% | 1.6% | 0.1 | 132 ft |
| Major County | 3,900 | 51% | 4.0% | 14.6 | 70 ft |
| Murray County | 3,800 | 27% | 3.0% | 1.0 | 130 ft |
| Noble County | 3,800 | 34% | 4.3% | 6.9 | 100 ft |
| Nowata County | 3,700 | 38% | 3.8% | 0.9 | 150 ft |
| Washita County | 3,600 | 32% | 4.0% | 10.4 | 120 ft |
| Kiowa County | 3,500 | 39% | 3.7% | 8.2 | 45 ft |
| Jackson County | 3,300 | 12% | 3.4% | 11.0 | 53 ft |
| Texas County | 3,200 | 16% | 5.6% | 5.5 | 300 ft |
| Blaine County | 3,000 | 33% | 3.9% | 12.5 | 65 ft |
| Beaver County | 2,600 | 49% | 3.6% | 5.2 | 180 ft |
| Dewey County | 2,400 | 54% | 2.9% | 6.5 | 120 ft |
| Coal County | 2,400 | 44% | 5.3% | 0.3 | 120 ft |
| Roger Mills County | 2,300 | 66% | 2.9% | 4.2 | 119 ft |
| Woods County | 2,000 | 24% | 3.2% | 7.7 | 60 ft |
| Alfalfa County | 1,900 | 39% | 4.3% | 13.3 | 50 ft |
| Cotton County | 1,800 | 31% | 6.9% | 6.4 | 80 ft |
| Greer County | 1,700 | 20% | 3.2% | 11.0 | 60 ft |
| Jefferson County | 1,500 | 28% | 4.5% | 6.0 | 120 ft |
| Grant County | 1,400 | 34% | 6.0% | 9.5 | 43 ft |
| Tillman County | 1,300 | 18% | 4.1% | 12.9 | 41 ft |
| Ellis County | 1,200 | 35% | 2.8% | 3.2 | 200 ft |
| Harper County | 960 | 29% | 3.2% | 5.9 | 80 ft |
| Cimarron County | 800 | 35% | 9.9% | 4.2 | 240 ft |
| Harmon County | 630 | 27% | 2.8% | 9.4 | 87 ft |
Shading: red is among the highest counties nationally, amber the middle, green the lower range. Click a column to sort.
Most well users above the arsenic limit
- Texas County: about 340 people
- Beaver County: about 290 people
- Lincoln County: about 260 people
- Pottawatomie County: about 240 people
- Grady County: about 230 people
Highest modeled nitrate
- Kingfisher County: 17.8 mg/L average (limit 10)
- Major County: 14.6 mg/L average (limit 10)
- Alfalfa County: 13.3 mg/L average (limit 10)
- Tillman County: 12.9 mg/L average (limit 10)
- Blaine County: 12.5 mg/L average (limit 10)
Test first, then treat what the test finds
We may earn a commission from links below, at no cost to you. Picks follow the testing order, not who pays. How we make money.
1. Certified lab well test
Start here, every year
A mail-in kit analyzed by a certified lab measures bacteria, nitrate, arsenic, metals and more. Test strips cannot measure arsenic or uranium reliably.
2. Sediment pre-filter
Sand, silt or cloudy water
A 5-micron cartridge after the pressure tank catches sand, silt and rust before they reach fixtures or other filters. Cartridges are cheap and swap every few months.
3. Iron and sulfur filter
Orange stains or rotten-egg smell
Air-injection or oxidizing-media filters remove orange staining and rotten-egg smell. Size one from a lab result for iron, manganese and hydrogen sulfide.
4. UV disinfection system
Coliform bacteria in a test
Inactivates bacteria and viruses; usually for private wells or after boil notices.
5. Under-sink reverse osmosis
Arsenic, nitrate or uranium in a test
The most thorough option for drinking water: PFAS, lead, nitrate, arsenic and more. Look for NSF/ANSI 58.
6. Whole-house well filter
Several problems at once
Multi-stage sediment and carbon for every tap. Add UV if bacteria shows up, and choose stages from your lab results, not a guess.
Questions
Which Oklahoma counties rely most on wells?+
By share of homes: Roger Mills County (66%), Atoka County (61%), Lincoln County (56%), Adair County (56%), Pushmataha County (56%). By number of people: Oklahoma County (80,200), Cleveland County (44,900), Pottawatomie County (29,600).
Is arsenic a problem in Oklahoma wells?+
USGS estimates about 4,300 Oklahoma well users have water above the 10 microgram per liter arsenic limit that applies to public systems, the largest numbers in Texas County, Beaver County, Lincoln County. Arsenic has no taste or smell, so only a lab test finds it.
Do I have to test my well when I sell a house in Oklahoma?+
We could not confirm a statewide rule for Oklahoma. Check with your county health department. Buyers can still make a lab test a condition of the offer.
How often should I test my well?+
No federal law covers private wells. EPA's drinking water limits apply to public water systems, so testing and treating a private well is up to the owner. EPA and CDC recommend testing at least once a year for coliform bacteria, nitrate, pH and total dissolved solids, and testing for arsenic, uranium, radon and other local concerns based on where you live.
Well-user counts, arsenic and nitrate figures are each a modeled estimate built from national datasets, not a count of tested wells, and well depths summarize drilling records rather than every well. Your own well can be very different from the county average, which is why the only answer for your home is a lab test. Sources: EPA Office of Research and Development, Water Source 2020 (private well estimates by census block); CDC Environmental Public Health Tracking, Well Water Index (from USGS nitrate and arsenic models); USGS, county-level domestic well population with arsenic above 10 micrograms per liter (Ayotte and others, 2017); USGS Synthesized Domestic Well Database for the Conterminous United States (SynDWell-US), McCarthy and others, 2025 (depth, where a county has 30+ usable records).