About 27% of the county's 4,995 residents. Rank 41 of 77 in Oklahoma.
95% range 27 to 44 private-well users (2010 base year). Rank 33 of 77 in Oklahoma.
Low potential (average indoor radon may be less than 2 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 Dewey 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:
- Oklahoma DEQ recommends testing every year for total coliform bacteria, nitrate/nitrite, conductivity and pH, especially for a new well or after work on the pipes, pressure tank, pump or well casing. If you have taste, odor or staining problems, it suggests testing sulfate, chloride, iron, manganese, hardness and corrosivity (pH and alkalinity) every three years. source
- DEQ says it is preferable to test for coliform bacteria and nitrate/nitrite early in a pregnancy, and recommends testing before bringing an infant home, especially if formula or food is prepared with well water. source
Arsenic. USGS estimates that about 35 people using private wells in Dewey County had arsenic above 10 µg/L, EPA's limit for public water (2010 base year; 95% range 27 to 44). 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 Dewey County in Zone 3: low potential (average indoor radon may be less than 2 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 |
|---|---|---|
| Texas County | 335 people (2010 base year) | |
| Beaver County | 285 people (2010 base year) | |
| Lincoln County | 264 people (2010 base year) | |
| Pottawatomie County | 238 people (2010 base year) | |
| Grady County | 225 people (2010 base year) | |
| Dewey County (this county) | 35 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 Dewey 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. 1 public system that serve ZIP codes mainly in Dewey County reported results. 0 of them had at least one sample with PFOA or PFOS at or above 4.0 ng/L, and 0 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.
Buying a home with a well in Dewey County
Loan test (FHA, VA, USDA) in Dewey County, OK
- 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.
Here:
- Oklahoma DEQ State Environmental Laboratory Services, Lab Services Fee Schedule FY27, effective July 1, 2026 through June 30, 2027: Daycare/real estate test list (total coliform and E. coli, nitrate, nitrite, lead), $104 (checked 2 Nov 2026) source
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 Dewey County
None of the labs on our Oklahoma list has an address in Dewey 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 Dewey County. Oklahoma DEQ State Environmental Laboratory Services, Lab Services Fee Schedule FY27, effective July 1, 2026 through June 30, 2027 publishes these prices: Private well annual test list (total coliform and E. coli, nitrate/nitrite, pH, conductivity) $75; Private well diagnostics test list (annual list plus calcium, copper, iron, manganese, sodium, hardness) $175; Daycare/real estate test list (total coliform and E. coli, nitrate, nitrite, lead) $104 (checked 2 Nov 2026) source. All Oklahoma state-lab prices and how to get a kit.
Labs on the Oklahoma list whose own websites say they take homeowner samples: ServiTech, Inc. - Dodge City (Dodge City). Use Check my ZIP to sort labs by distance.
See all Oklahoma 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)
- ODEQ Lab Facility Search - laboratories accredited by the DEQ Laboratory Accreditation Program (Matrix: Drinking Water) (Live database, searched 2026-11-02)
Filter by the test you need and by labs that take homeowner samples.
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