About 24% of the county's 66,520 residents. Rank 14 of 115 in Missouri.
95% range 144 to 220 private-well users (2010 base year). Rank 21 of 115 in Missouri.
Moderate potential (average indoor radon may be between 2 and 4 pCi/L). EPA says the map should not be used to decide whether an individual home needs testing.
Labs with an address in this county, from the official state lists on this site, matched by ZIP code.
What to test for in St. Francois County
Private wells are not regulated like public water: EPA advises owners to test their well every year for total coliform bacteria, nitrates, total dissolved solids and pH. Your state's own schedule:
- The Missouri Department of Health and Senior Services (DHSS) recommends testing your well at least once a year, and any time the well is serviced or the water changes in look, smell or taste. source
- DHSS says to test each year for total coliform bacteria, E. coli and nitrate, and for other contaminants you suspect. Also test if there are known well water problems in your area, after flooding, land disturbance or nearby waste disposal, or after you repair or replace any part of the well system. If you live in an area with current or past mining, DHSS recommends a metals test. source
Arsenic. USGS estimates that about 178 people using private wells in St. Francois County had arsenic above 10 µg/L, EPA's limit for public water (2010 base year; 95% range 144 to 220). USGS describes this kind of estimate as useful "for broad screening of the population at risk", so it says nothing certain about any one well. Arsenic has no taste or smell: test for it by name.
Radon. EPA puts St. Francois County in Zone 2: moderate potential (average indoor radon may be between 2 and 4 pCi/L). That map is about radon in indoor air, and EPA says it should not be used to decide whether an individual home needs testing. If radon is found in your air and you have a well, EPA suggests testing the water too: see radon in well water.
For anything specific to your home (farms nearby, old plumbing, a new baby, a smell or stain), use the which-tests checklist. When the results arrive, check your numbers against EPA's limits.
Show the numbers
| Item | Value | Note |
|---|---|---|
| Greene County | 618 people (2010 base year) | |
| Lincoln County | 548 people (2010 base year) | |
| Pettis County | 488 people (2010 base year) | |
| Franklin County | 467 people (2010 base year) | |
| Camden County | 434 people (2010 base year) | |
| St. Francois County (this county) | 178 people (2010 base year) |
USGS model estimate for broad screening, not a measurement of any well. Only a test tells you about your own well. Source: USGS, Estimated county level domestic well population with arsenic greater than 10 micrograms per liter (Ayotte, Medalie and Qi, 2017), accessed 2026-11-01.
PFAS in public water near St. Francois County (public supply, not your well)
This is public water data, not your well. A private well draws its own groundwater, which can have more or less PFAS than the public supply nearby. Only a test of your well tells you.
Under EPA’s fifth Unregulated Contaminant Monitoring Rule (UCMR 5), public water systems sampled their water for 29 PFAS between Jan 3, 2023 and Jun 17, 2026. 7 public systems that serve ZIP codes mainly in St. Francois County reported results. 0 of them had at least one sample with PFOA or PFOS at or above 4.0 ng/L, and 2 had at least one of the 29 PFAS measured at or above its reporting level.
4.0 ng/L (parts per trillion) is both EPA’s UCMR 5 reporting level for PFOA and PFOS and the number in EPA’s 2024 limit for public water. That limit is judged on a running annual average, so one sample at that level is not a violation. EPA proposed changes to its PFAS rules in May 2026: see PFAS in well water for the current status and who should test a well. To test your own well, find a lab certified for PFAS.
Method: a system counts for this county when it reports serving a ZIP code whose largest land part is in this county, so a system serving several counties counts in each. Source: U.S. EPA, UCMR 5 occurrence data (by state), file dated Oct 15, 2026; downloaded Nov 1, 2026.
Testing programs and help in Missouri
- Get a sample collection kit from your local public health agency. Some counties also send a representative to test your well. source
- The DHSS Private Drinking Water Program gives homeowners technical help with water testing, understanding results and treatment. source
Buying a home with a well in St. Francois County
Loan test (FHA, VA, USDA) in St. Francois County, MO
- VA. Test results are valid for 90 days from the date the local health authority certifies them, unless the local authority says otherwise. VA’s chapter names no list of contaminants: the water must meet the local health authority’s requirements, or EPA guidelines where it has none. Your lender may ask for specific tests.
- FHA. A well test is required in the situations FHA’s handbook lists, among others, and the report may not be more than 180 days old at disbursement.
- USDA. Guaranteed loans need a water quality test for a private well, done by the local health authority or a state-certified lab, and no more than 180 days old at closing.
Lenders can ask for more (extra tests, a particular lab, who takes the sample): ask your lender before you book. Federal rules as read on Nov 3, 2026 source 1 source 2 source 3. Full comparison: VA, FHA and USDA well water test requirements. Loan test kits sold by mail, with price and days to results: kits compared.
State-certified labs in St. Francois County
None of the labs on our Missouri list has an address in St. Francois County. Labs elsewhere in the state may take samples by mail or courier: ask the lab, and check the hold time for bacteria before you send one.
Testing by mail from St. Francois County. Missouri State Public Health Laboratory, Bacteriology Private Water Test Request form MO 580-3168 publishes these prices: Routine well bacteria test (total coliform and E. coli), handling fee $10 (checked 2 Nov 2026) source. All Missouri state-lab prices and how to get a kit.
Labs on the Missouri list whose own websites say they take homeowner samples: Christian County Health Department Water Lab (Ozark), IIA Lab Services LLC (St. Louis), Missouri Department of Health & Senior Services-State Public Health Laboratory (Jefferson City), Newton County Health Department Laboratory (Neosho), Taney County Health Department Laboratory (Branson), Water Smart Testing LLC (Rolla). Use Check my ZIP to sort labs by distance.
See all Missouri labs in the finder and filter by the test you need and by labs that take homeowner samples.
- USGS, Estimated use of water in the United States, county-level data for 2015 (Dieter et al., ver. 2.0, 2018)
- USGS, Estimated county level domestic well population with arsenic greater than 10 micrograms per liter (Ayotte, Medalie and Qi, 2017)
- U.S. EPA, Map of Radon Zones, county list (EPA 402/A-16/001)
- U.S. Census Bureau, 2020 ZCTA to county relationship file (lab ZIP codes to counties)
- Missouri DNR - Certified Chemical Laboratories (spreadsheet of all laboratories) (Live export fetched 2026-11-15 (no list date printed in the file))
Filter by the test you need and by labs that take homeowner samples.
Open the finder →