About 36% of the county's 10,676 residents. Rank 52 of 99 in Iowa.
95% range 113 to 161 private-well users (2010 base year). Rank 71 of 99 in Iowa.
Highest potential (average indoor radon may be greater than 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 Guthrie 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:
- Iowa DNR says every private well used for drinking should be tested at least once a year. Also test when the well is new, after any work on the well, pump or water system, and when the water looks, smells or tastes different. source
- For the tests covered by the Private Well Grants program, Iowa DNR lists bacteria (coliform and E. coli) and nitrate every year, and arsenic and manganese every three years. source
Arsenic. USGS estimates that about 135 people using private wells in Guthrie County had arsenic above 10 µg/L, EPA's limit for public water (2010 base year; 95% range 113 to 161). 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 Guthrie County in Zone 1: highest potential (average indoor radon may be greater than 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 |
|---|---|---|
| Kossuth County | 1,662 people (2010 base year) | |
| Webster County | 1,543 people (2010 base year) | |
| Boone County | 1,532 people (2010 base year) | |
| Hancock County | 1,397 people (2010 base year) | |
| Dallas County | 967 people (2010 base year) | |
| Guthrie County (this county) | 135 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 Guthrie 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. 3 public systems that serve ZIP codes mainly in Guthrie 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.
Testing programs and help in Iowa
- Iowa's Private Well Grants program provides free water testing to private well owners through county environmental health offices. Iowa DNR says nearly all counties take part; ask your county office whether yours does and to arrange sampling. source
- The standard free tests are nitrate, bacteria, manganese and arsenic. A county health specialist must collect the sample. Requests to cover other tests are reviewed case by case. source
- The same program reimburses qualifying well services done by a DNR-certified contractor, at actual cost up to $400 for shock chlorination, $600 for a well assessment, $700 for well plugging, $400 for cistern plugging and $2,000 for well reconstruction or rehabilitation. Contact your county health department before the work starts. source
Buying a home with a well in Guthrie County
Loan test (FHA, VA, USDA) in Guthrie County, IA
- 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 Guthrie County
None of the labs on our Iowa list has an address in Guthrie 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.
Labs on the Iowa list whose own websites say they take homeowner samples: AgSource (Ellsworth), ChemRight Laboratories (Maquoketa), Dubuque - City Environmental Monitoring Lab (Dubuque), Dubuque County Health Department (Dubuque). Use Check my ZIP to sort labs by distance.
See all Iowa 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)
- Iowa DNR LabCert - List of Certified Labs (Drinking Water program) + Find a Lab analyte search + Lab Details (Date Generated: 11/14/2026 (LabCert, live database))
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