Arsenic is widespread in Montgomery County wells.
1 widespread, 3 worth checking, 2 rare out of 6 health checks.
From 48 wells tested in Montgomery County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: radon (5).
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 12 people 73,983 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 Montgomery County compares with Pennsylvania and the counties around it.
Each result puts Montgomery County next to the 6 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Montgomery County wells.
Arsenic7 of 31 wells over
Too few tested to show: Delaware, Lehigh, Philadelphia.
These 3 are worth checking in Montgomery County.
Manganese2 of 31 wells over
Too few tested to show: Delaware, Lehigh, Philadelphia.
Nitrate2 of 31 wells over
Too few tested to show: Delaware, Lehigh, Philadelphia.
These 2 are rare in Montgomery County.
Lead0 of 28 wells over
Too few tested to show: Delaware, Lehigh, Philadelphia.
Uranium0 of 28 wells over
Too few tested to show: Delaware, Lehigh, Philadelphia.
Too few Montgomery County wells were tested for this one.
Radon in water5 wells tested
Coliform bacteria turned up in 19 of 28 tested Montgomery County wells, so test for it every year.
Coliform bacteria19 of 28 wells had it
Too few tested to show: Delaware, Lehigh, Philadelphia.
E. coli2 of 21 wells had it
Too few tested to show: Delaware, Lehigh, Philadelphia.
E. coli means human or animal waste is getting in, so if a test of your Montgomery County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 2 of 31 tested wells, and it isn't a health risk.
Iron stains2 of 31 wells had it
Too few tested to show: Delaware, Lehigh, Philadelphia.
Most of the 48 wells tested in Montgomery 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 Montgomery 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 Montgomery County.
- Bacteria
- Nitrate
- Arsenic
- Manganese
- Fluoride
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 Montgomery County.
Montgomery 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 17 town water systems in Montgomery County test for PFAS. 14 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 235 ng/L of PFOA. Only 4 wells in Montgomery County have 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 Montgomery County
Is well water in Montgomery County safe to drink?
7 of 31 wells tested in Montgomery County had arsenic over the limit, about 2 in 10. Across Pennsylvania it's about 1 in 24. That's the highest share among the 23 Pennsylvania counties with 10 or more tested wells. So test your own well for arsenic before you count on it.
Where can I get my well tested in Montgomery 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, arsenic, manganese and fluoride, the tests that matter most in Montgomery County.
How does Montgomery County compare with the counties around it?
For arsenic, the share of tested wells over the limit: Montgomery County, at 23%, had a higher share than all 3 neighboring counties with data. Groundwater doesn't stop at county lines, so Berks's 13% is worth knowing about if you live near it.
How often should I test my well in Montgomery County?
In Montgomery County, 19 of 28 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 Montgomery County numbers come from
- People on wells: 73,983 in Montgomery County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 390 well water samples from 48 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Neighboring counties: the 6 counties that share a border with Montgomery County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 17 town water systems in Montgomery County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Montgomery County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Protection, checked November 1, 2026.