Quick answer
About 871,000 people in Missouri (14.5% of residents) got their water from private wells in 2010, according to USGS estimates. Missouri Department of Health and Senior Services runs the state’s private well guidance. We didn’t find a free statewide well testing program in Missouri. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
- People on private wells
- 870,614
- Share of residents
- 14.5%
- Rank among states
- 16th
- Well users modeled above 10 µg/L arsenic
- 2.1%
Where to get your well tested in Missouri
- Missouri Department of Health and Senior Services: Private Drinking Water Program, the state’s guidance for private well owners.
- Well water testing in Missouri: what to test for and how to collect a sample.
- Certified laboratories in Missouri. 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 Missouri. 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 Missouri 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 |
|---|---|---|---|
| Jefferson County | 38,395 | 17.6% | 2.3% |
| Franklin County | 37,305 | 36.8% | 1.9% |
| Greene County | 31,839 | 11.6% | 1.4% |
| Newton County | 28,318 | 48.7% | 1.0% |
| Camden County | 21,422 | 48.7% | 1.1% |
| Webster County | 21,129 | 58.4% | 1.0% |
| Howell County | 20,305 | 50.3% | 1.0% |
| St. Francois County | 19,474 | 29.8% | 2.3% |
| Lincoln County | 19,357 | 36.8% | 2.7% |
| Christian County | 18,596 | 24.0% | 1.1% |
| Washington County | 18,435 | 73.2% | 1.6% |
| Phelps County | 17,946 | 39.7% | 1.0% |
Show all 115 counties
| Jasper County | 17,544 | 14.9% | 1.2% |
| Barry County | 16,773 | 47.1% | 1.1% |
| Polk County | 16,722 | 53.7% | 1.0% |
| Lawrence County | 16,371 | 42.4% | 1.4% |
| Stone County | 16,037 | 49.8% | 1.0% |
| St. Charles County | 15,617 | 4.3% | 5.4% |
| Miller County | 14,845 | 60.0% | 1.5% |
| Morgan County | 13,513 | 65.7% | 1.7% |
| Taney County | 13,367 | 25.9% | 1.1% |
| Crawford County | 12,824 | 51.9% | 1.0% |
| Dallas County | 12,579 | 75.0% | 1.0% |
| Cape Girardeau County | 12,188 | 16.1% | 2.3% |
| Butler County | 12,072 | 28.2% | 2.3% |
| McDonald County | 11,868 | 51.4% | 1.0% |
| Texas County | 11,694 | 45.0% | 1.0% |
| Cole County | 11,392 | 15.0% | 2.0% |
| Pettis County | 11,333 | 26.9% | 2.6% |
| Scott County | 10,816 | 27.6% | 13.7% |
| Wright County | 10,728 | 57.0% | 1.0% |
| Benton County | 10,676 | 56.0% | 1.3% |
| Warren County | 10,497 | 32.3% | 2.0% |
| Douglas County | 9,718 | 71.0% | 1.0% |
| St. Louis County | 9,625 | 1.0% | 2.5% |
| Laclede County | 9,188 | 25.8% | 1.0% |
| Bollinger County | 9,115 | 73.7% | 1.6% |
| Stoddard County | 8,716 | 29.1% | 6.2% |
| Dent County | 8,685 | 55.5% | 1.0% |
| Pulaski County | 8,489 | 16.2% | 1.0% |
| Ozark County | 7,912 | 81.4% | 1.0% |
| Wayne County | 7,598 | 56.2% | 1.0% |
| Callaway County | 7,048 | 15.9% | 1.9% |
| Johnson County | 7,026 | 13.4% | 2.2% |
| Ste. Genevieve County | 6,914 | 38.1% | 3.5% |
| Gasconade County | 6,860 | 45.1% | 1.2% |
| Ripley County | 6,813 | 48.3% | 1.0% |
| Osage County | 6,735 | 48.5% | 2.0% |
| Maries County | 6,710 | 73.1% | 1.0% |
| Oregon County | 6,368 | 58.5% | 1.0% |
| Hickory County | 6,314 | 65.6% | 1.0% |
| Perry County | 5,831 | 30.7% | 2.0% |
| St. Clair County | 5,814 | 59.3% | 3.1% |
| Madison County | 5,766 | 47.2% | 1.5% |
| Henry County | 5,719 | 25.7% | 2.0% |
| Moniteau County | 5,529 | 35.4% | 2.0% |
| Iron County | 5,435 | 51.1% | 1.1% |
| Cedar County | 5,364 | 38.4% | 2.7% |
| Mississippi County | 4,939 | 34.4% | 17.6% |
| Montgomery County | 4,756 | 38.9% | 3.5% |
| Boone County | 4,671 | 2.9% | 1.8% |
| Cooper County | 4,615 | 26.2% | 3.0% |
| Reynolds County | 4,603 | 68.7% | 1.0% |
| Shannon County | 4,366 | 51.7% | 1.0% |
| Audrain County | 4,143 | 16.2% | 3.0% |
| Pike County | 4,112 | 22.2% | 5.6% |
| New Madrid County | 4,043 | 21.3% | 7.5% |
| Nodaway County | 3,797 | 16.2% | 2.6% |
| Carter County | 3,410 | 54.4% | 1.0% |
| Dade County | 3,333 | 42.3% | 2.0% |
| Clinton County | 3,190 | 15.4% | 2.0% |
| Dunklin County | 2,903 | 9.1% | 8.2% |
| Saline County | 2,680 | 11.5% | 5.3% |
| Vernon County | 2,616 | 12.4% | 2.1% |
| Marion County | 2,606 | 9.1% | 3.6% |
| DeKalb County | 2,547 | 19.8% | 2.2% |
| Ralls County | 2,506 | 24.6% | 3.0% |
| Jackson County | 2,473 | 0.4% | 2.8% |
| Ray County | 2,388 | 10.2% | 2.2% |
| Cass County | 2,334 | 2.3% | 1.1% |
| Clay County | 2,311 | 1.0% | 2.5% |
| Caldwell County | 2,214 | 23.5% | 2.0% |
| Lewis County | 2,069 | 20.3% | 2.4% |
| Andrew County | 2,017 | 11.7% | 4.9% |
| Monroe County | 1,987 | 22.5% | 3.0% |
| Bates County | 1,865 | 10.9% | 1.3% |
| Clark County | 1,845 | 25.8% | 2.5% |
| Platte County | 1,816 | 2.0% | 3.0% |
| Daviess County | 1,749 | 20.7% | 3.0% |
| Gentry County | 1,593 | 23.6% | 3.0% |
| Buchanan County | 1,537 | 1.7% | 2.5% |
| Holt County | 1,522 | 31.0% | 8.8% |
| Harrison County | 1,513 | 16.9% | 1.5% |
| Carroll County | 1,418 | 15.3% | 3.0% |
| Atchison County | 1,284 | 22.6% | 8.2% |
| Howard County | 1,237 | 12.2% | 2.0% |
| Schuyler County | 1,117 | 25.2% | 2.4% |
| Lafayette County | 1,107 | 3.3% | 2.3% |
| Chariton County | 1,064 | 13.6% | 3.8% |
| Putnam County | 998 | 20.0% | 2.0% |
| Livingston County | 955 | 6.3% | 3.8% |
| Randolph County | 946 | 3.7% | 1.5% |
| Knox County | 908 | 22.0% | 1.2% |
| Scotland County | 884 | 18.3% | 2.0% |
| Mercer County | 851 | 22.5% | 2.0% |
| Macon County | 844 | 5.4% | 2.0% |
| Shelby County | 802 | 12.6% | 2.5% |
| Adair County | 739 | 2.9% | 1.4% |
| Sullivan County | 602 | 9.0% | 2.3% |
| Worth County | 574 | 26.4% | 3.0% |
| Linn County | 484 | 3.8% | – |
| Pemiscot County | 457 | 2.5% | – |
| Grundy County | 396 | 3.9% | – |
| Barton County | 390 | 3.1% | – |
| St. Louis city | 219 | 0.1% | – |
Counties with the highest modeled arsenic share: Mississippi County (17.6%), Scott County (13.7%), Holt County (8.8%), Dunklin County (8.2%), Atchison County (8.2%).
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 Missouri offer free well water testing?
We didn’t find a free statewide well testing program in Missouri. Certified labs charge for each test, and some county health departments offer lower-cost bacteria and nitrate tests.
Who oversees private wells in Missouri?
Missouri Department of Health and Senior Services (Private Drinking Water 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 Missouri?
USGS estimates about 871,000 people, or 14.5% of the population in 2010. That ranks 16th of the states covered by the estimate.
What should I test my well for in Missouri?
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
- Missouri Department of Health and Senior Services: Private Drinking Water Program
- Missouri Department of Health and Senior Services: well water testing
- Missouri 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)