Nitrate and manganese are worth checking in Warren County wells.
2 worth checking, 3 rare out of 5 health checks.
From 23 wells tested in Warren County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (8), radon (7).
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 3 people 40,775 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 Warren County compares with New Jersey and the counties around it.
Each result puts Warren County next to the 6 counties that border it, on the chart's 0 to 50% scale.
These 2 are worth checking in Warren County.
Nitrate3 of 23 wells over
Too few tested to show: Monroe, PA.
Manganese2 of 23 wells over
Too few tested to show: Monroe, PA, Northampton, PA.
These 3 are rare in Warren County.
Arsenic0 of 22 wells over
Too few tested to show: Monroe, PA, Northampton, PA.
Lead0 of 16 wells over
Too few tested to show: Monroe, PA, Northampton, PA.
Too few Warren County wells were tested for these 2.
Uranium8 wells tested
Radon in water7 wells tested
Coliform bacteria turned up in 1 of 6 tested Warren County wells, so test for it every year.
Coliform bacteria1 of 6 wells had it
E. coli0 of 6 wells had it
E. coli means human or animal waste is getting in, so if a test of your Warren County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 0 of 23 tested wells, and it isn't a health risk.
Iron stains0 of 23 wells had it
Too few tested to show: Monroe, PA, Northampton, PA.
Most of the 23 wells tested in Warren County were last tested before 2010.
An old result shows the water as it was then, so treat these 23 wells as a starting point and test your own.
Most Warren 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 Warren County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
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 200 feet.
That comes from 316 wells in New Jersey's drilling records. Most wells of every kind here are 150 to 300 feet deep. Wells as deep as Warren 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 wells on record here go deeper than in 10 of the 19 other 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 Warren County.
Warren 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 Warren County test for PFAS. 2 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 9.1 ng/L of PFOA. Only 10 wells in Warren 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 Warren County
Is well water in Warren County safe to drink?
3 of 23 wells tested in Warren County had nitrate over the limit, about 1 in 8. Across New Jersey it's about 1 in 13. That's a bigger share than in 13 of the 15 other New Jersey counties with 10 or more tested wells. So test your own well for nitrate before you count on it.
Where can I get my well tested in Warren 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, manganese and arsenic, the tests that matter most in Warren County.
How deep are wells in Warren County?
Half the wells on record here are shallower than 200 feet. Typical wells on record here go deeper than in 10 of the 19 other New Jersey counties with enough drilling records.
How does Warren County compare with the counties around it?
For nitrate, the share of tested wells over the limit: 1 of the 5 neighboring counties with data had a higher share than Warren County, at 13%. Northampton, PA had the most, at 27%. Groundwater doesn't stop at county lines, so Northampton, PA's 27% is worth knowing about if you live near it.
How often should I test my well in Warren County?
In Warren County, 1 of 6 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 Warren County numbers come from
- People on wells: 40,775 in Warren County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 424 well water samples from 23 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2022.
- Well depths: 316 New Jersey drilling records for Warren County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Warren County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 6 town water systems in Warren County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Warren County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Protection, checked November 1, 2026.