Radon is widespread in Baltimore County wells.
1 widespread, 1 worth checking, 3 rare out of 5 health checks.
From 174 wells tested in Baltimore County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: arsenic (9), uranium (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 9 people 98,261 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 Baltimore County compares with Maryland and the counties around it.
Each result puts Baltimore County next to the 7 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Baltimore County wells.
Radon in water22 of 59 wells over
Too few tested to show: Baltimore city, Carroll, Harford, Kent.
This one is worth checking in Baltimore County.
Manganese17 of 123 wells over
Too few tested to show: Baltimore city, Harford, Howard, York, PA.
These 3 are rare in Baltimore County.
Nitrate8 of 166 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Baltimore city, Howard.
Lead1 of 53 wells over
Too few tested to show: Baltimore city, Harford, Howard, Kent, York, PA.
Fluoride0 of 77 wells over
Too few tested to show: Baltimore city, Harford, Howard, York, PA.
Too few Baltimore County wells were tested for these 2.
Arsenic9 wells tested
Uranium5 wells tested
Every well needs a bacteria test every year.
No bacteria tests from Baltimore County wells are in the public data. Test every year anyway.
Iron reached staining levels in 30 of 167 tested wells, and it isn't a health risk.
Iron stains30 of 167 wells had it
Too few tested to show: Baltimore city, Howard, York, PA.
Most of the 174 wells tested in Baltimore County were last tested before 2010.
An old result shows the water as it was then, so treat these 174 wells as a starting point and test your own.
Most Baltimore 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 Baltimore County.
- Bacteria
- Nitrate
- Radon in water
- Manganese
- Arsenic
What Maryland offers well owners
- Free testingWe didn't find a free program for all of Maryland. Maryland's private well page
- Certified labsMaryland's list of certified labs
- Well recordsWe didn't find an online search.
- New wellsSince October 1, 2024, Md. Code, Real Property 10-713 requires a contract for sale of property with a private well to make well water quality testing a condition of sale, with both parties certifying they reviewed the results.
Half the household wells here are shallower than 200 feet.
That comes from 32,140 household wells in Maryland's drilling records. Most wells of every kind here are 125 to 300 feet deep. Wells as deep as Baltimore 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 12 of the 23 other Maryland counties with enough drilling records.
How to find your own well's depth
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in Baltimore County.
Baltimore 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 2 town water systems in Baltimore County test for PFAS. 1 found some PFAS, all below the new limits. No well in Baltimore 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 Baltimore County
Is well water in Baltimore County safe to drink?
22 of 59 wells tested in Baltimore County had radon in water over the limit, about 4 in 10. Across Maryland it's about 1 in 10. That's the highest share among the 11 Maryland counties with 10 or more tested wells. So test your own well for radon in water before you count on it.
Where can I get my well tested in Baltimore County?
Use a lab Maryland has certified for drinking water. Maryland's list is linked above, in the box about testing. Ask for bacteria, nitrate, radon in water, manganese and arsenic, the tests that matter most in Baltimore County.
How deep are wells in Baltimore County?
Half the household wells here are shallower than 200 feet. Typical household wells here go deeper than in 12 of the 23 other Maryland counties with enough drilling records.
How does Baltimore County compare with the counties around it?
For radon in water, the share of tested wells over the limit: Baltimore County, at 37%, had a higher share than all 3 neighboring counties with data. Groundwater doesn't stop at county lines, so Howard's 20% is worth knowing about if you live near it.
How often should I test my well in Baltimore County?
Baltimore County has no public bacteria results for wells, so follow the CDC's advice: 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 Baltimore County numbers come from
- People on wells: 98,261 in Baltimore County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,457 well water samples from 174 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2020.
- Well depths: 32,140 Maryland drilling records for Baltimore County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 7 counties that share a border with Baltimore County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 2 town water systems in Baltimore County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Baltimore County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Maryland Department of the Environment, checked November 1, 2026.