Manganese, radon and arsenic are worth checking in Dauphin County wells.
3 worth checking, 1 rare out of 4 health checks.
From 48 wells tested in Dauphin County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (4), lead (4), fluoride (4).
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 5 people 59,080 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
Radon risk (a gas from rock)
Likely here. Test your home's air first.
Radon zones: EPA map
Here's how Dauphin County compares with Pennsylvania and the counties around it.
Each result puts Dauphin County next to the 8 counties that border it, on the chart's 0 to 50% scale.
These 3 are worth checking in Dauphin County.
Manganese4 of 37 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Cumberland, Juniata, Lebanon, Perry, York.
Radon in water3 of 36 wells over
Too few tested to show: Juniata, Northumberland, Perry, Schuylkill.
Arsenic2 of 30 wells over
Too few tested to show: Cumberland, Juniata, Perry, Schuylkill.
This one is rare in Dauphin County.
Nitrate0 of 37 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Juniata, Perry, Schuylkill.
Too few Dauphin County wells were tested for these 3.
Uranium4 wells tested
Lead4 wells tested
Fluoride4 wells tested
Coliform bacteria turned up in 28 of 35 tested Dauphin County wells, so test for it every year.
Coliform bacteria28 of 35 wells had it
Too few tested to show: Juniata, Lebanon, Northumberland, Perry, Schuylkill, York.
E. coli1 of 8 wells had it
E. coli means human or animal waste is getting in, so if a test of your Dauphin County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 5 of 44 tested wells, and it isn't a health risk.
Iron stains5 of 44 wells had it
Too few tested to show: Cumberland, Juniata, Lebanon, Perry, York.
Most of the 48 wells tested in Dauphin County were last tested before 2010.
An old result shows the water as it was then, so treat these 48 wells as a starting point and test your own.
Most Dauphin 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 5 things to check in Dauphin County.
- Bacteria
- Nitrate
- Manganese
- Radon in water
- Arsenic
What Pennsylvania offers well owners
- Free testingWe didn't find a free program for all of Pennsylvania. Pennsylvania's private well page
- Certified labsPennsylvania's list of certified labs
- Well recordsPennsylvania's well record search
Here's what we know about radon and PFAS in Dauphin County.
Dauphin 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 7 town water systems in Dauphin County test for PFAS. 3 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 13 ng/L of PFOS. No well in Dauphin 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 Dauphin County
Is well water in Dauphin County safe to drink?
4 of 37 wells tested in Dauphin County had manganese over the limit, about 1 in 9. Across Pennsylvania it's about 1 in 11. That's a bigger share than in 11 of the 17 other Pennsylvania counties with 10 or more tested wells, leaving out 2 counties whose results are likely overstated. So test your own well for manganese before you count on it.
Where can I get my well tested in Dauphin County?
Use a lab Pennsylvania has certified for drinking water. Pennsylvania's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese, radon in water and arsenic, the tests that matter most in Dauphin County.
How does Dauphin County compare with the counties around it?
For manganese, the share of tested wells over the limit: 1 of the 3 neighboring counties with data had a higher share than Dauphin County, at 11%. Lancaster had the most, at 21%. Groundwater doesn't stop at county lines, so Lancaster's 21% is worth knowing about if you live near it.
How often should I test my well in Dauphin County?
In Dauphin County, 28 of 35 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 Dauphin County numbers come from
- People on wells: 59,080 in Dauphin County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 308 well water samples from 48 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Neighboring counties: the 8 counties that share a border with Dauphin County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 7 town water systems in Dauphin County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Dauphin County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Protection, checked November 1, 2026.