New York Private Well Water Risk: Arsenic & Nitrate
These figures are USGS statistical estimates for private (domestic) wells in New York. They describe the area's modeled risk — not any single well.
Quick answer: Yes — arsenic occurs naturally in New York groundwater. USGS modeling estimates about 66,265 New York residents rely on private wells with arsenic above the EPA limit of 10 µg/L. The highest modeled exposure is in Suffolk County (~6,834), Steuben County (~4,077), St. Lawrence County (~2,885). For nitrate, about 0% of New York's ~1,850,000 private-well residents are modeled above the 10 mg/L limit. These are area estimates, not a test of your well — arsenic has no taste or smell, so only a certified lab test tells you your level.
This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.
Nitrate
0%
of the private-well population is modeled above the 10 mg/L nitrate limit
~0
people on wells estimated above the limit
~1,850,000
total residents on private wells statewide
Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.
Find out what's actually in your well
New York has one of the higher modeled arsenic exposures in the country — but that number is an area estimate, not your well. Arsenic, nitrate and coliform bacteria are the three most common private-well problems, and none of them has a taste or smell. A certified lab test checks all of them at once; the CDC and EPA recommend testing every well at least once a year.
Basic screening only. Confirm arsenic, nitrate and bacteria with a certified lab.
Find a certified drinking-water labAmazon links are affiliate links — we may earn a commission at no extra cost to you.
Arsenic
Across New York, an estimated ~66,265 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Suffolk County (~6,834 people).
Counties with the highest modeled arsenic exposure
| County | Est. well residents over arsenic limit | 90% range |
|---|---|---|
| Suffolk County | ~6,834 | 4,337–10,721 |
| Steuben County | ~4,077 | 2,800–5,849 |
| St. Lawrence County | ~2,885 | 2,290–3,622 |
| Erie County | ~2,800 | 1,906–4,090 |
| Wyoming County | ~2,661 | 1,832–3,798 |
| Tioga County | ~2,484 | 1,704–3,573 |
| Broome County | ~2,482 | 1,705–3,563 |
| Yates County | ~2,426 | 1,685–3,391 |
| Washington County | ~2,130 | 1,552–2,894 |
| Cattaraugus County | ~1,965 | 1,325–2,878 |
| Onondaga County | ~1,733 | 1,385–2,251 |
| Genesee County | ~1,728 | 1,383–2,358 |
| Columbia County | ~1,688 | 1,225–2,290 |
| Orange County | ~1,660 | 1,232–2,318 |
| Chenango County | ~1,632 | 1,151–2,307 |
| Otsego County | ~1,409 | 1,049–1,891 |
| Allegany County | ~1,371 | 939–1,985 |
| Ontario County | ~1,300 | 938–1,855 |
| Clinton County | ~1,237 | 950–1,624 |
| Chautauqua County | ~1,188 | 787–1,771 |
| Dutchess County | ~1,177 | 941–1,476 |
| Orleans County | ~1,163 | 976–1,402 |
| Schuyler County | ~1,159 | 787–1,680 |
| Cortland County | ~1,114 | 766–1,621 |
| Saratoga County | ~1,101 | 876–1,402 |
| Putnam County | ~1,064 | 820–1,398 |
| Ulster County | ~950 | 743–1,228 |
| Livingston County | ~931 | 663–1,288 |
| Rensselaer County | ~827 | 632–1,087 |
| Seneca County | ~816 | 587–1,156 |
| Cayuga County | ~758 | 557–1,082 |
| Oneida County | ~660 | 513–870 |
| Monroe County | ~654 | 545–844 |
| Montgomery County | ~626 | 511–774 |
| Westchester County | ~600 | 446–820 |
| Schoharie County | ~539 | 435–673 |
| Franklin County | ~529 | 422–666 |
| Fulton County | ~506 | 380–691 |
| Herkimer County | ~499 | 397–634 |
| Sullivan County | ~482 | 392–599 |
| Greene County | ~470 | 371–595 |
| Wayne County | ~423 | 333–645 |
| Delaware County | ~421 | 325–546 |
| Oswego County | ~402 | 317–516 |
| Madison County | ~400 | 326–493 |
| Schenectady County | ~386 | 317–474 |
| Niagara County | ~356 | 285–474 |
| Lewis County | ~286 | 221–370 |
| Tompkins County | ~280 | 190–407 |
| Warren County | ~267 | 208–353 |
| Chemung County | ~243 | 165–347 |
| Jefferson County | ~243 | 188–318 |
10 additional New York counties have lower modeled arsenic exposure (fewer than 100 estimated well residents over the limit). Of these, 9 have measured USGS well samples: Albany, Bronx, Essex, Hamilton, Kings, Nassau, New York, Queens, Richmond.
Source: USGS domestic-well arsenic model, Lombard et al. (2021); county population product (2017).
Measured well tests by county
The USGS has published laboratory results from wells in 61 New York counties (at least 5 wells each). These are real measurements of other wells — domestic, public-supply and monitoring wells — not a test of yours. The tables rank counties by the share of sampled wells over each federal threshold.
Nitrate (as N): counties with the most wells > 10 mg/L (EPA MCL)
| County | Wells over | Median | Sampled |
|---|---|---|---|
| Kings County | 15% | 5.7 mg/L | 27 wells |
| Nassau County | 11% | 3.4 mg/L | 94 wells |
| Montgomery County | 10% | 0 mg/L | 52 wells |
| Washington County | 8% | 0 mg/L | 12 wells |
| Schenectady County | 8% | 0.5 mg/L | 12 wells |
| Queens County | 6% | 4.6 mg/L | 80 wells |
| Richmond County | 5% | 1 mg/L | 20 wells |
| Albany County | 4% | 0 mg/L | 24 wells |
| Erie County | 3% | 1.6 mg/L | 29 wells |
| Suffolk County | 2% | 0.2 mg/L | 119 wells |
Manganese: counties with the most wells > 300 µg/L (EPA health advisory)
| County | Wells over | Median | Sampled |
|---|---|---|---|
| Richmond County | 44% | 214 µg/L | 18 wells |
| Kings County | 31% | 2 µg/L | 29 wells |
| Broome County | 29% | 179 µg/L | 17 wells |
| Ulster County | 23% | 60 µg/L | 22 wells |
| Chemung County | 21% | 87 µg/L | 19 wells |
| Suffolk County | 20% | 50 µg/L | 211 wells |
| Onondaga County | 18% | 61 µg/L | 34 wells |
| Steuben County | 18% | 18 µg/L | 28 wells |
| Columbia County | 18% | 12 µg/L | 11 wells |
| Tioga County | 17% | 60 µg/L | 12 wells |
Source: USGS ScienceBase 5f36baa782cee144fb3873e8 (manganese, pH, arsenic) and McMahon et al. (2019), Environ. Sci. Technol. 53:29–38 (nitrate, iron); aggregated by county with Census 2020 boundaries. USGS well samples; not a test of your well.
Acidic well water in New York (low pH)
36% of 1,989 USGS-sampled wells in New York had pH below 6.5. Acidic water corrodes copper pipes and fixtures and can leach lead and copper into your tap water — the usual fix is a whole-house acid neutralizer (calcite for mildly acidic water, soda-ash injection for very low pH). Counties with the highest share of acidic wells:
| County | Wells below pH 6.5 | Median pH | Sampled |
|---|---|---|---|
| Suffolk County | 86% | 5.9 | 363 wells |
| Nassau County | 80% | 5.9 | 345 wells |
| New York County | 73% | 6.2 | 11 wells |
| Putnam County | 50% | 6.5 | 8 wells |
| Queens County | 46% | 6.6 | 108 wells |
| Richmond County | 33% | 6.9 | 21 wells |
| Greene County | 28% | 7.6 | 36 wells |
| Sullivan County | 27% | 6.6 | 11 wells |
| Westchester County | 24% | 7.2 | 17 wells |
| Kings County | 22% | 7.0 | 67 wells |
Source: USGS ScienceBase 5f36baa782cee144fb3873e8 (pH). Measured other wells, not a test of yours.
Match the filter to your test result
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New York well water: FAQ
Is there arsenic in well water in New York?
Yes. USGS modeling estimates about 66,265 people in New York use private wells with arsenic above 10 µg/L, across 62 modeled counties. Arsenic comes from natural bedrock and varies well to well, even between neighbors, so a lab test is the only way to know your own level.
Which New York counties have the most arsenic in well water?
By modeled number of well residents over the arsenic limit: Suffolk County (~6,834), Steuben County (~4,077), St. Lawrence County (~2,885). Counties with more private-well users rank higher, so a smaller county can still have a high share of affected wells.
How do I remove arsenic from well water in New York?
Test first. If arsenic is present, a point-of-use reverse-osmosis system under the kitchen sink removes 90%+ of it; boiling does not remove arsenic (it concentrates it), and carbon pitchers and water softeners do not remove it either. Whole-house adsorptive arsenic media is used when levels are high. Re-test after installing and then annually.
Is nitrate a problem in New York well water?
USGS models about 0% of New York's private-well population (~0 people) above the 10 mg/L nitrate limit. Nitrate is highest in shallow wells near fertilized cropland, septic systems or livestock, and matters most for infants and pregnancy.
Do I need an acid neutralizer for my well in New York?
Acidic well water is common in New York. In USGS lab results from 1,989 wells across 60 New York counties, 36% had pH below 6.5. The most acidic sampled counties are Suffolk County (86% of 363 wells), Nassau County (80% of 345 wells), New York County (73% of 11 wells). You only need a neutralizer if your own well tests below about 6.5 — signs include blue-green stains on fixtures and pinhole leaks in copper pipe. A calcite (or calcite/Corosex) neutralizer tank handles mildly acidic water (roughly pH 6–6.5); very acidic water usually needs soda-ash injection. Test first-draw lead and copper too, since acidic water dissolves both from plumbing.
High manganese in New York well water — what should I do?
In USGS lab results from 1,616 wells across 58 New York counties, 12% were above the EPA's 300 µg/L health advisory for manganese and 37% were above the 50 µg/L level where it stains fixtures and laundry black or brown. Sampled counties with the highest share over the health advisory: Richmond County (44% of 18 wells), Kings County (31% of 29 wells), Broome County (29% of 17 wells). If your own test is over 300 µg/L, don't use the water for infant formula and use another source for drinking and cooking until it is treated — high manganese is linked to neurological effects, especially in babies and children. Boiling does not remove it. For the whole house, an oxidizing filter (greensand, Birm or air-injection) handles manganese, usually alongside iron; a water softener can remove low levels. For drinking water, a point-of-use reverse osmosis system reduces manganese at the kitchen tap. Retest after treatment to confirm it worked.