Manganese is widespread in Monmouth County wells.
1 widespread, 1 worth checking, 4 rare out of 6 health checks.
From 53 wells tested in Monmouth County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: radon (6).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
About 1 in 17 people 37,489 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Middle depth: some shelter from the surface, not complete.
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 Monmouth County compares with New Jersey and the counties around it.
Each result puts Monmouth County next to the 6 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Monmouth County wells.
Manganese11 of 51 wells over
This one is worth checking in Monmouth County.
Nitrate2 of 37 wells over
These 4 are rare in Monmouth County.
Uranium0 of 12 wells over
Too few tested to show: Queens, NY, Richmond, NY.
Arsenic0 of 48 wells over
Lead0 of 26 wells over
Fluoride0 of 40 wells over
Too few Monmouth County wells were tested for this one.
Radon in water6 wells tested
None of the 2 Monmouth County wells tested for bacteria had it, but every well needs a yearly test.
Coliform bacteria0 of 2 wells had it
E. coli0 of 2 wells had it
E. coli means human or animal waste is getting in, so if a test of your Monmouth County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 35 of 51 tested wells, and it isn't a health risk.
Iron stains35 of 51 wells had it
About 4 in 10 of the 53 wells tested in Monmouth County have a test from 2020 or later.
With 22 wells tested since 2020, age matters less here than who did the testing and why.
Most Monmouth 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 Monmouth 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 100 feet.
That comes from 8,430 wells in New Jersey's drilling records. Most wells of every kind here are 75 to 150 feet deep. Wells as deep as Monmouth 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 are shallower than in 12 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 Monmouth County.
Monmouth 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 24 town water systems in Monmouth County test for PFAS. 17 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 8.3 ng/L of PFOA. Only 12 wells in Monmouth 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 Monmouth County
Is well water in Monmouth County safe to drink?
11 of 51 wells tested in Monmouth County had manganese over the limit, about 2 in 10. Across New Jersey it's about 1 in 8. That's a bigger share than in 15 of the 16 other New Jersey 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 Monmouth 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 Monmouth County.
How deep are wells in Monmouth County?
Half the wells on record here are shallower than 100 feet. Typical wells on record here are shallower than in 12 of the 19 other New Jersey counties with enough drilling records.
How does Monmouth County compare with the counties around it?
For manganese, the share of tested wells over the limit: 3 of the 6 neighboring counties with data had a higher share than Monmouth County, at 22%. Richmond, NY had the most, at 43%. Groundwater doesn't stop at county lines, so Richmond, NY's 43% is worth knowing about if you live near it.
How often should I test my well in Monmouth County?
None of the 2 wells tested for bacteria in Monmouth County had it, but the CDC still says to 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 Monmouth County numbers come from
- People on wells: 37,489 in Monmouth County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 679 well water samples from 53 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Well depths: 8,430 New Jersey drilling records for Monmouth County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Monmouth County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 24 town water systems in Monmouth County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Monmouth County is zone 1 on the EPA Map of Radon Zones.
- State programs and links: Department of Environmental Protection, checked November 1, 2026.