New York well water by county: arsenic and nitrate
Modelled arsenic and nitrate for private-well users in every New York county, what to test for, and where to find a certified lab. Private wells aren’t covered by the Safe Drinking Water Act.
All 62 counties
- Suffolk CountyWell users 119,100Arsenic about 8 in 100Nitrate 0.8 mg/L
- Dutchess CountyWell users 97,100Arsenic about 4 in 100Nitrate 0.3 mg/L
- Orange CountyWell users 85,200Arsenic about 2 in 100Nitrate 0.2 mg/L
- Ulster CountyWell users 81,500Arsenic about 4 in 100Nitrate 0.2 mg/L
- St. Lawrence CountyWell users 54,900Arsenic about 5 in 100Nitrate 0.1 mg/L
- Oswego CountyWell users 52,900Arsenic about 4 in 100Nitrate 0.1 mg/L
- Saratoga CountyWell users 51,800Arsenic about 5 in 100Nitrate 0.1 mg/L
- Broome CountyWell users 51,300Arsenic about 8 in 100Nitrate 0.1 mg/L
- Rensselaer CountyWell users 50,900Arsenic about 5 in 100Nitrate 0.1 mg/L
- Westchester CountyWell users 49,400Arsenic about 6 in 100Nitrate 1.1 mg/L
- Oneida CountyWell users 47,600Arsenic about 5 in 100Nitrate 0.2 mg/L
- Putnam CountyWell users 46,900Arsenic about 5 in 100Nitrate 0.7 mg/L
- Erie CountyWell users 45,000Arsenic about 11 in 100Nitrate 0.1 mg/L
- Steuben CountyWell users 44,300Arsenic about 7 in 100Nitrate 0.1 mg/L
- Chautauqua CountyWell users 42,600Arsenic about 7 in 100Nitrate 0.2 mg/L
- Sullivan CountyWell users 40,600Arsenic about 3 in 100Nitrate 0.2 mg/L
- Columbia CountyWell users 38,000Arsenic about 6 in 100Nitrate 0.1 mg/L
- Jefferson CountyWell users 36,600Arsenic about 3 in 100Nitrate 0.1 mg/L
- Clinton CountyWell users 33,900Arsenic about 5 in 100Nitrate 0.2 mg/L
- Onondaga CountyWell users 33,800Arsenic about 4 in 100Nitrate 0.5 mg/L
- Cattaraugus CountyWell users 33,600Arsenic about 5 in 100Nitrate 0.1 mg/L
- Washington CountyWell users 31,800Arsenic about 6 in 100Nitrate 0.1 mg/L
- Tioga CountyWell users 29,900Arsenic about 7 in 100Nitrate 0.1 mg/L
- Tompkins CountyWell users 29,300Arsenic about 7 in 100Nitrate 0.2 mg/L
- Otsego CountyWell users 28,300Arsenic about 6 in 100Nitrate 0.2 mg/L
- Chenango CountyWell users 27,000Arsenic about 7 in 100Nitrate 0.1 mg/L
- Cayuga CountyWell users 26,700Arsenic about 7 in 100Nitrate 0.5 mg/L
- Madison CountyWell users 26,400Arsenic about 7 in 100Nitrate 0.3 mg/L
- Genesee CountyWell users 26,100Arsenic about 15 in 100Nitrate 0.3 mg/L
- Chemung CountyWell users 25,800Arsenic about 6 in 100Nitrate 0.2 mg/L
- Greene CountyWell users 25,300Arsenic about 5 in 100Nitrate 0.0 mg/L
- Ontario CountyWell users 24,200Arsenic about 12 in 100Nitrate 0.2 mg/L
- Wayne CountyWell users 23,000Arsenic about 7 in 100Nitrate 0.2 mg/L
- Allegany CountyWell users 22,700Arsenic about 8 in 100Nitrate 0.0 mg/L
- Franklin CountyWell users 22,500Arsenic about 4 in 100Nitrate 0.1 mg/L
- Albany CountyWell users 22,400Arsenic about 5 in 100Nitrate 0.1 mg/L
- Wyoming CountyWell users 21,500Arsenic about 29 in 100Nitrate 0.1 mg/L
- Delaware CountyWell users 21,300Arsenic about 5 in 100Nitrate 0.1 mg/L
- Livingston CountyWell users 21,200Arsenic about 19 in 100Nitrate 0.2 mg/L
- Fulton CountyWell users 21,000Arsenic about 4 in 100Nitrate 0.2 mg/L
- Herkimer CountyWell users 20,600Arsenic about 3 in 100Nitrate 0.3 mg/L
- Schoharie CountyWell users 20,000Arsenic about 4 in 100Nitrate 0.1 mg/L
- Orleans CountyWell users 19,300Arsenic about 27 in 100Nitrate 0.4 mg/L
- Montgomery CountyWell users 18,600Arsenic about 5 in 100Nitrate 0.1 mg/L
- Rockland CountyWell users 17,500Arsenic about 2 in 100Nitrate 1.9 mg/L
- Cortland CountyWell users 17,300Arsenic about 6 in 100Nitrate 0.3 mg/L
- Monroe CountyWell users 17,300Arsenic about 13 in 100Nitrate 0.8 mg/L
- Warren CountyWell users 15,000Arsenic about 5 in 100Nitrate 0.0 mg/L
- Lewis CountyWell users 13,300Arsenic about 2 in 100Nitrate 0.1 mg/L
- Yates CountyWell users 13,000Arsenic about 15 in 100Nitrate 0.2 mg/L
- Seneca CountyWell users 12,600Arsenic about 13 in 100Nitrate 0.2 mg/L
- Schuyler CountyWell users 12,100Arsenic about 11 in 100Nitrate 0.1 mg/L
- Schenectady CountyWell users 11,700Arsenic about 4 in 100Nitrate 0.2 mg/L
- Essex CountyWell users 9,300Arsenic about 3 in 100Nitrate 0.1 mg/L
- Niagara CountyWell users 6,200Arsenic about 11 in 100Nitrate 0.2 mg/L
- Kings CountyWell users 5,100Arsenic about 6 in 100Nitrate 0.8 mg/L
- Nassau CountyWell users 4,900Arsenic about 6 in 100Nitrate 1.2 mg/L
- Queens CountyWell users 3,900Arsenic about 6 in 100Nitrate 1.7 mg/L
- Hamilton CountyWell users 2,300Arsenic about 2 in 100Nitrate 0.0 mg/L
- Bronx CountyWell users 1,200Arsenic about 7 in 100Nitrate 0.5 mg/L
- New York CountyWell users 830Arsenic about 8 in 100Nitrate 0.4 mg/L
- Richmond CountyWell users 210Arsenic about 3 in 100Nitrate 1.8 mg/L
Each mark = 1 in 100 well users the model places above 10 µg/L arsenic (scale 0–10)10 mg/L nitrate: the federal limit (MCL) for public systems
- These figures describe the area, not your well. Only a lab test shows what’s in your water.
- CDC says the Well Water Index figures “do not describe risk to individual wells.” (CDC Tracking Network)
- The arsenic model is better at spotting low-arsenic areas than at confirming high ones.
- Well-user counts are 2010 USGS estimates; tract values are averages over each census tract.
- Total coliform bacteriaEvery year
- NitrateEvery year
- Total dissolved solidsEvery year
- pHEvery year
- ArsenicAsk your local health department
EPA: Private Drinking Water Wells · CDC: Guidelines for Testing Well Water
Use a state-certified lab
New York State Department of Health lists the laboratories certified to test drinking water in New York.
Screening tells you if something is worth a closer look
A lab result is the number you can act on.
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Lab-certified results
ETR Labs Basic Water Quality Test Kit
ETR Laboratories
50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria
- Analyzed by Environmental Testing and Research Laboratories (ETR Labs), Leominster, MA · ISO/IEC 17025:2017, ANAB certificate AT-2638
- Turnaround: 2–4 business days after the lab receives it
What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.
Screening: quick check, not lab-grade
Watersafe Drinking Water Test Kit
Silver Lake Research
Lead, bacteria, nitrate, copper, iron, chlorine, hardness and pH
- Turnaround: Minutes; the bacteria test can take up to 48 hours
What it can't tell you: Each test gives a yes/no or a rough range, not a lab number, and it cannot detect PFAS or arsenic.
A mail-in kit’s lab is accredited (ISO/IEC 17025) but may not be certified by your state. For a home sale, a loan, or a health-department follow-up, use a state-certified lab.
New York well water
Sources: CDC Well Water Index (2024) · USGS arsenic and nitrate models · USGS domestic well populations · EPA and CDC testing guidance. Data last updated 2026-10-08. All sources →
How many people use private wells in New York?
About 1.9 million people across 62 New York counties, by the USGS 2010 estimate. USGS models place about 121,100 of them in areas where wells are likely to be above the 10 µg/L arsenic limit. These are area estimates, not well results.
Are private wells regulated in New York?
The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws. (EPA) Testing and treatment are the owner's responsibility.
Where can I get my well tested in New York?
New York State Department of Health keeps the list of laboratories certified to test drinking water in New York. Only use laboratories that are certified to do drinking water testing. (EPA)