Manganese, arsenic and radon are worth checking in Sullivan County wells.

3 worth checking, 4 rare out of 7 health checks.

From 17 wells tested in Sullivan County since 2001; your own well needs its own test. How to read this

Tested wells over the limit SullivanNew York

Manganese6%1 of 17 Arsenic6%1 of 17 Radon6%1 of 17 Nitrate0%0 of 17 Lead0%0 of 17 Uranium0%0 of 17 Fluoride0%0 of 17

GermsTest every year, whatever the chart says

Coliform bacteria18%3 of 17 E. coli0%0 of 13

StainsNot a health risk

Iron stains6%1 of 17

Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+

Lab results: Water Quality Portal (USGS and EPA)

Show bacteria and iron

Who drinks from a well here

6 in 10 people 43,303 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)

LowMiddleHigh

Likely here. Test your home's air first.

Radon zones: EPA map

Here's how Sullivan County compares with New York and the counties around it.

Each result puts Sullivan County next to the 5 counties that border it, on the chart's 0 to 50% scale.

These 3 are worth checking in Sullivan County.

Manganese1 of 17 wells over

1 of 17 wells tested here from 2001 to 2020 was over the EPA health advisory of 0.3 mg/L, against about 1 in 7 across New York. Half the results were under 0.0052 mg/L, and the top 1 in 10 were 0.09 mg/L or more. That's a smaller share than in 27 of the 50 other New York counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated.

Sullivan and its neighbors

Orange25%

Ulster16%

Pike, PA15%

Sullivan6%

Delaware4%

Wayne, PA1%

Manganese guide

Arsenic1 of 17 wells over

1 of 17 wells tested here from 2001 to 2020 was over the EPA limit of 10 µg/L, against about 1 in 28 across New York. Half the results were under 0.5 µg/L, and the top 1 in 10 were 6.2 µg/L or more. That's a bigger share than in 36 of the 49 other New York counties with 10 or more tested wells.

Sullivan and its neighbors

Ulster6%

Sullivan6%

Wayne, PA4%

Pike, PA1%

Delaware0%

Orange0%

Arsenic guide

Radon in water1 of 17 wells over

1 of 17 wells tested here from 2001 to 2020 was over 4,000 pCi/L, a level the EPA proposed, against under 1 in 50 across New York. Half the results were under 1,210 pCi/L, and the top 1 in 10 were 2,750 pCi/L or more. That's a bigger share than in 40 of the 45 other New York counties with 10 or more tested wells.

Sullivan and its neighbors

Wayne, PA13%

Orange8%

Sullivan6%

Pike, PA4%

Delaware0%

Ulster0%

Radon guide

These 4 are rare in Sullivan County.

Nitrate0 of 17 wells over

None of the 17 wells tested here from 2001 to 2020 were over the EPA limit of 10 mg/L, against about 1 in 35 across New York. Half the results were under 0.31 mg/L, and the top 1 in 10 were 1.3 mg/L or more. Sullivan County had none, while 9 of the 51 other New York counties with 10 or more tested wells had at least one.

Sullivan and its neighbors

Delaware0%

Orange0%

Pike, PA0%

Sullivan0%

Ulster0%

Wayne, PA0%

Nitrate guide

Lead0 of 17 wells over

None of the 17 wells tested here from 2001 to 2020 were over the EPA action level of 15 µg/L, against about 1 in 40 across New York. Half the results were under 0.39 µg/L, and the top 1 in 10 were 1.8 µg/L or more. Sullivan County had none, while 3 of the 51 other New York counties with 10 or more tested wells had at least one.

Sullivan and its neighbors

Delaware0%

Orange0%

Pike, PA0%

Sullivan0%

Ulster0%

Wayne, PA0%

Lead guide

Uranium0 of 17 wells over

None of the 17 wells tested here from 2001 to 2020 were over the EPA limit of 30 µg/L, against under 1 in 100 across New York. Half the results were under 0.31 µg/L, and the top 1 in 10 were 2.1 µg/L or more. Sullivan County had none, while 3 of the 46 other New York counties with 10 or more tested wells had at least one.

Sullivan and its neighbors

Delaware0%

Orange0%

Pike, PA0%

Sullivan0%

Ulster0%

Wayne, PA0%

Uranium guide

Fluoride0 of 17 wells over

None of the 17 wells tested here from 2001 to 2020 were over the EPA limit of 4 mg/L, against under 1 in 100 across New York. Half the results were under 0.07 mg/L, and the top 1 in 10 were 0.11 mg/L or more. Sullivan County had none, while 2 of the 51 other New York counties with 10 or more tested wells had at least one.

Sullivan and its neighbors

Delaware0%

Orange0%

Pike, PA0%

Sullivan0%

Ulster0%

Wayne, PA0%

Coliform bacteria turned up in 3 of 17 tested Sullivan County wells, so test for it every year.

Coliform bacteria3 of 17 wells had it

3 of 17 wells tested here from 2001 to 2020 had coliform bacteria, against about 1 in 4 across New York.

Sullivan and its neighbors

Pike, PA35%

Wayne, PA32%

Delaware27%

Orange25%

Ulster20%

Sullivan18%

Bacteria guide

E. coli0 of 13 wells had it

None of the 13 wells tested here from 2001 to 2020 had E. coli, against about 1 in 26 across New York.

Sullivan and its neighbors

Wayne, PA10%

Orange8%

Ulster7%

Delaware6%

Pike, PA0%

Sullivan0%

E. coli means human or animal waste is getting in, so if a test of your Sullivan County well finds it, boil drinking water until the well is fixed.

Bacteria guide

Iron reached staining levels in 1 of 17 tested wells, and it isn't a health risk.

Iron stains1 of 17 wells had it

1 of 17 wells tested here from 2001 to 2020 had enough iron to stain (0.3 mg/L), against about 4 in 10 across New York.

Sullivan and its neighbors

Pike, PA41%

Ulster34%

Orange25%

Delaware11%

Wayne, PA9%

Sullivan6%

Iron guide

Sullivan County has 17 tested wells, and the busiest decade for testing was the 2010s.

6 wells had a test in the 2000s, 10 in the 2010s and 5 since 2020.

Only 5 of the 17 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.

Most Sullivan 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 Sullivan County.

Bacteria
Nitrate
Arsenic
Radon in water
Manganese

What New York offers well owners

Free testingThe Private Well PFAS Testing and Mitigation Rebate Pilot Program offers limited free PFAS testing and treatment rebates in Dutchess, Orange, Putnam, Suffolk, Ulster and Westchester counties. See the program
Certified labsNew York's list of certified labs
Well recordsNew York's well record search

Half the household wells here are shallower than 300 feet.

That comes from 4,489 household wells in New York's drilling records. Most wells of every kind here are 225 to 420 feet deep. Wells as deep as Sullivan 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 48 of the 56 other New York counties with enough drilling records.

Look up your own well's depth in New York'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 Sullivan County.

Sullivan 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 Sullivan County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 4.6 ng/L of PFOA. No well in Sullivan 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

Next door to Sullivan County

Orange Ulster

Elsewhere in New York

St. Lawrence Saratoga Oneida Oswego Rensselaer Steuben

All of New York

Questions people ask about well water in Sullivan County

Is well water in Sullivan County safe to drink?

1 of 17 wells tested in Sullivan County had arsenic over the limit, about 1 in 17. Across New York it's about 1 in 28. That's a bigger share than in 36 of the 49 other New York counties with 10 or more tested wells. So test your own well for arsenic before you count on it.

Can I get my well tested for free in Sullivan County?

The Private Well PFAS Testing and Mitigation Rebate Pilot Program offers limited free PFAS testing and treatment rebates in Dutchess, Orange, Putnam, Suffolk, Ulster and Westchester counties. If not, use a lab New York has certified for drinking water. Ask for bacteria, nitrate, arsenic, radon in water and manganese, the tests that matter most in Sullivan County.

How deep are wells in Sullivan County?

Half the household wells here are shallower than 300 feet. Typical household wells here go deeper than in 48 of the 56 other New York counties with enough drilling records.

How does Sullivan County compare with the counties around it?

For manganese, the share of tested wells over the limit: 3 of the 5 neighboring counties with data had a higher share than Sullivan County, at 6%. Orange had the most, at 25%. Groundwater doesn't stop at county lines, so Orange's 25% is worth knowing about if you live near it.

How often should I test my well in Sullivan County?

In Sullivan County, 3 of 17 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.

By the Tested Water teamData from the USGS, EPA and Department of HealthUpdated November 8, 2026

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Where the Sullivan County numbers come from

People on wells: 43,303 in Sullivan County, from EPA estimates built on the 2020 Census (Murray et al.).
Lab tests: 225 well water samples from 17 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2020.
Well depths: 4,489 New York drilling records for Sullivan County, gathered in the US Groundwater Well Database (Lin and others, 2024).
Neighboring counties: the 5 counties that share a border with Sullivan County, from the Census Bureau's county adjacency file.
PFAS: EPA tests of 6 town water systems in Sullivan County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
Radon: Sullivan County is zone 1 on the EPA Map of Radon Zones.
State programs and links: Department of Health, checked November 1, 2026.

Download this county's data (CSV)How we read these numbers Report an error