Manganese is widespread in Barnstable County wells.
1 widespread, 1 worth checking, 4 rare out of 6 health checks.
From 824 wells tested in Barnstable County since 2000; your own well needs its own test. How to read this
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 6 people 35,295 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Shallow wells: watch for fertilizer and germs from above.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Barnstable County compares with Massachusetts and the counties around it.
Each result puts Barnstable County next to the 3 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Barnstable County wells.
Manganese36 of 168 wells over
Too few tested to show: Bristol, Dukes.
This one is worth checking in Barnstable County.
Nitrate88 of 721 wells over
Too few tested to show: Bristol, Dukes.
These 4 are rare in Barnstable County.
Arsenic2 of 77 wells over
Too few tested to show: Bristol, Dukes.
Uranium0 of 21 wells over
Too few tested to show: Bristol, Dukes.
Lead0 of 33 wells over
Too few tested to show: Bristol, Dukes.
Fluoride0 of 46 wells over
Too few tested to show: Bristol, Dukes.
Every well needs a bacteria test every year.
No bacteria tests from Barnstable County wells are in the public data. Test every year anyway.
Iron reached staining levels in 54 of 164 tested wells, and it isn't a health risk.
Iron stains54 of 164 wells had it
Too few tested to show: Bristol, Dukes.
Barnstable County has 824 tested wells, and the busiest decade for testing was the 2000s.
Only 237 of the 824 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Barnstable 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 Barnstable County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
What Massachusetts offers well owners
- Free testingWe didn't find a free program for all of Massachusetts. Massachusetts's private well page
- Certified labsMassachusetts's list of certified labs
- Well recordsMassachusetts's well record search
Half the household wells here are shallower than 54 feet.
That comes from 8,662 household wells in Massachusetts's drilling records. Most wells of every kind here are 39 to 70 feet deep. Wells as shallow as Barnstable County's pick up bacteria and nitrate from the surface more easily, so the yearly test matters even more here. That's the shallowest typical depth for household wells among the 14 Massachusetts counties with enough drilling records.
Look up your own well's depth in Massachusetts'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 Barnstable County.
Barnstable County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 20 town water systems in Barnstable 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 7.1 ng/L of PFOS. Only 45 wells in Barnstable 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 Barnstable County
Is well water in Barnstable County safe to drink?
36 of 168 wells tested in Barnstable County had manganese over the limit, about 2 in 10. Across Massachusetts it's about 2 in 10. That's a bigger share than in 2 of the 4 other Massachusetts counties with 10 or more tested wells. So test your own well for manganese before you count on it.
Where can I get my well tested in Barnstable County?
Use a lab Massachusetts has certified for drinking water. Massachusetts's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in Barnstable County.
How deep are wells in Barnstable County?
Half the household wells here are shallower than 54 feet. That's the shallowest typical depth for household wells among the 14 Massachusetts counties with enough drilling records.
How does Barnstable County compare with the counties around it?
For manganese, the share of tested wells over the limit: Plymouth, the one neighbor with data, came in higher than Barnstable County, at 26% against 21%. Groundwater doesn't stop at county lines, so Plymouth's 26% is worth knowing about if you live near it.
How often should I test my well in Barnstable County?
Barnstable 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 Barnstable County numbers come from
- People on wells: 35,295 in Barnstable County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 3,670 well water samples from 824 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Well depths: 8,662 Massachusetts drilling records for Barnstable County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 3 counties that share a border with Barnstable County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 20 town water systems in Barnstable County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Barnstable County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Massachusetts Department of Environmental Protection (MassDEP), checked November 1, 2026.