Arsenic is widespread in Hunterdon County wells.
1 widespread, 1 likely overstated, 1 worth checking, 4 rare out of 7 health checks.
From 39 wells tested in Hunterdon County since 2000; your own well needs its own test. How to read this
*Radon: All of these tests come from the US Geological Survey between 2006 and 2011, so this likely overstates it.
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
6 in 10 people 76,425 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 Hunterdon County compares with New Jersey and the counties around it.
Each result puts Hunterdon County next to the 5 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Hunterdon County wells.
Arsenic8 of 37 wells over
This one has turned up often here, mostly in older study samples.
Radon in water7 of 13 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Mercer, Morris, Somerset, Warren.
All of these tests come from the US Geological Survey between 2006 and 2011, so this likely overstates it.
This one is worth checking in Hunterdon County.
Manganese3 of 38 wells over
These 4 are rare in Hunterdon County.
Uranium1 of 21 wells over
Too few tested to show: Somerset, Warren.
Nitrate0 of 37 wells over
Lead0 of 12 wells over
Too few tested to show: Somerset.
Coliform bacteria turned up in 4 of 15 tested Hunterdon County wells, so test for it every year.
Coliform bacteria4 of 15 wells had it
Too few tested to show: Mercer, Morris, Somerset, Warren.
E. coli1 of 15 wells had it
Too few tested to show: Mercer, Morris, Somerset, Warren.
E. coli means human or animal waste is getting in, so if a test of your Hunterdon County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 3 of 38 tested wells, and it isn't a health risk.
Iron stains3 of 38 wells had it
Hunterdon County has 39 tested wells, and the busiest decade for testing was the 2010s.
Only 8 of the 39 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Hunterdon 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 Hunterdon County.
- Bacteria
- Nitrate
- Radon in water
- Arsenic
- Manganese
What New Jersey offers well owners
- Free testingWe didn't find a free program for all of New Jersey. New Jersey's private well page
- Certified labsNew Jersey's list of certified labs
- Well recordsNew Jersey's well record search
- New wellsUnder the Private Well Testing Act (N.J.S.A. 58:12A-26 et seq.), every sale of property with a private potable well requires a water test before closing of title, and landlords must test at least every five years.
Half the wells on record here are shallower than 250 feet.
That comes from 545 wells in New Jersey's drilling records. Most wells of every kind here are 200 to 300 feet deep. Wells as deep as Hunterdon 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. That's the deepest typical depth for wells on record among the 20 New Jersey counties with enough drilling records.
Look up your own well's depth in New Jersey'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 Hunterdon County.
Hunterdon 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 6 town water systems in Hunterdon County test for PFAS. 5 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 12 ng/L of PFOS. Only 8 wells in Hunterdon 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 Hunterdon County
Is well water in Hunterdon County safe to drink?
7 of 13 wells tested in Hunterdon County had radon in water over the limit, about 5 in 10. Across New Jersey it's about 1 in 9. We don't rank this against other New Jersey counties, because most of these tests are old study samples. All of these tests come from the US Geological Survey between 2006 and 2011, so this likely overstates it. So test your own well for radon in water before you count on it.
Where can I get my well tested in Hunterdon County?
Use a lab New Jersey has certified for drinking water. New Jersey's list is linked above, in the box about testing. Ask for bacteria, nitrate, radon in water, arsenic and manganese, the tests that matter most in Hunterdon County.
How deep are wells in Hunterdon County?
Half the wells on record here are shallower than 250 feet. That's the deepest typical depth for wells on record among the 20 New Jersey counties with enough drilling records.
How does Hunterdon County compare with the counties around it?
For radon in water, the share of tested wells over the limit: Bucks, PA, the one neighbor with data, came in lower than Hunterdon County, at 6% against 54%. Groundwater doesn't stop at county lines, so Bucks, PA's 6% is worth knowing about if you live near it.
How often should I test my well in Hunterdon County?
In Hunterdon County, 4 of 15 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 Hunterdon County numbers come from
- People on wells: 76,425 in Hunterdon County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 469 well water samples from 39 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2022.
- Well depths: 545 New Jersey drilling records for Hunterdon County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 5 counties that share a border with Hunterdon County, from the Census Bureau's county adjacency file.
- Results marked likely overstated: our own check of who tested the wells, when and where.
- PFAS: EPA tests of 6 town water systems in Hunterdon County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Hunterdon County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Protection, checked November 1, 2026.