Manganese is widespread in Linn County wells.
1 widespread, 1 worth checking, 3 rare out of 5 health checks.
From 77 wells tested in Linn County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (6), radon (3).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
1 in 11 people 20,996 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Deep wells: fewer surface germs, more minerals from the rock.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Likely here. Test your home's air first.
Radon zones: EPA map
Here's how Linn County compares with Iowa and the counties around it.
Each result puts Linn County next to the 7 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Linn County wells.
Manganese28 of 74 wells over
Too few tested to show: Cedar.
This one is worth checking in Linn County.
Nitrate5 of 51 wells over
Too few tested to show: Buchanan, Cedar, Delaware, Jones.
These 3 are rare in Linn County.
Arsenic2 of 44 wells over
Too few tested to show: Cedar.
Fluoride0 of 74 wells over
Too few tested to show: Cedar.
Lead0 of 44 wells over
Too few tested to show: Cedar.
Too few Linn County wells were tested for these 2.
Uranium6 wells tested
Radon in water3 wells tested
Coliform bacteria turned up in 7 of 12 tested Linn County wells, so test for it every year.
Coliform bacteria7 of 12 wells had it
E. coli4 of 13 wells had it
E. coli means human or animal waste is getting in, so if a test of your Linn County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 16 of 74 tested wells, and it isn't a health risk.
Iron stains16 of 74 wells had it
Too few tested to show: Cedar.
Most of the 77 wells tested in Linn County were last tested before 2010.
An old result shows the water as it was then, so treat these 77 wells as a starting point and test your own.
Most Linn County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 4 things to check in Linn County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
What Iowa offers well owners
- Free testingIowa's Private Well Grants program provides free testing for bacteria, nitrate, arsenic, and manganese through participating county environmental health offices. See the program
- Certified labsIowa's list of certified labs
- Well recordsIowa's well record search
Half the household wells here are shallower than 227 feet.
That comes from 1,534 household wells in Iowa's drilling records. Most wells of every kind here are 115 to 275 feet deep. Wells as deep as Linn County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. Typical household wells here go deeper than in 70 of the 92 other Iowa counties with enough drilling records.
Look up your own well's depth in Iowa's well record search, or see how to find it.
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in Linn County.
Linn County is in the EPA's highest radon zone. Radon from well water adds to the radon in your indoor air, so test your air first, and your water too if the air is high. Radon guide
Between 2023 and 2025 the EPA had 4 town water systems in Linn County test for PFAS. 1 found some PFAS, all below the new limits. No well in Linn County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in Linn County
Is well water in Linn County safe to drink?
28 of 74 wells tested in Linn County had manganese over the limit, about 4 in 10. Across Iowa it's about 2 in 10. That's a bigger share than in 54 of the 67 other Iowa counties with 10 or more tested wells. So test your own well for manganese before you count on it.
Can I get my well tested for free in Linn County?
Iowa's Private Well Grants program provides free testing for bacteria, nitrate, arsenic, and manganese through participating county environmental health offices. If not, use a lab Iowa has certified for drinking water. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in Linn County.
How deep are wells in Linn County?
Half the household wells here are shallower than 227 feet. Typical household wells here go deeper than in 70 of the 92 other Iowa counties with enough drilling records.
How does Linn County compare with the counties around it?
For manganese, the share of tested wells over the limit: Linn County, at 38%, had a higher share than all 6 neighboring counties with data. Groundwater doesn't stop at county lines, so Johnson's 18% is worth knowing about if you live near it.
How often should I test my well in Linn County?
In Linn County, 7 of 12 tested wells had coliform bacteria, so the CDC's advice matters here: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the Linn County numbers come from
- People on wells: 20,996 in Linn County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 3,066 well water samples from 77 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Well depths: 1,534 Iowa drilling records for Linn County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 7 counties that share a border with Linn County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 4 town water systems in Linn County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Linn County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Iowa Department of Natural Resources, checked November 1, 2026.