Well water in Jefferson County, New York
In Jefferson County, none of 112 tested well samples exceeded the EPA limit for fluoride, based on public data from USGS Water Quality Portal.
The strongest signal is coliform bacteria: Recommended for every private well, every year, too few samples to carry the headline but first on the test list below.
707 test results across 12 contaminants from at least 60 wells, 1951 to 2020; chloride has the most at 123. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 29,710 people in Jefferson County get their drinking water from a private well, per USGS 2015 county water use. That is about 25% of residents.
Separately, the USGS national arsenic model estimates that <1% of the 29,710 people on private wells in Jefferson County draw water above 10 ug/L (the model's range is <1% to 1%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Jefferson County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Fluoride 1951 to 2020 | 112 | 96% | 0.2 | 1.73 | 4 mg/L EPA limit | |
| Nitrate 1973 to 2020 | 43 | 72% | 0.2 | 9 | 10 mg/L EPA limit | |
| Arsenic 1971 to 2020 | 38 | 53% | 0.04 | 8 | 10 ug/L EPA limit | |
| Copper 1971 to 2020 | 38 | 71% | 0.003 | 0.64 | 1.3 mg/L EPA limit | |
| Lead 1971 to 2020 | 38 | 82% | 0.12 | 9.8 | 15 ug/L EPA limit | |
| Uranium 2005 to 2020 | 31 | 84% | 0.28 | 3.06 | 30 ug/L EPA limit | |
| E. coli 2008 to 2020 | 14 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Chloride 1951 to 2020 | no limit | 123 | 100% | 6 | 1,080 | 250 mg/L nuisance level |
| Iron 1951 to 2020 | no limit | 112 | 96% | 54.5 | 45,500 | 300 ug/L nuisance level |
| Manganese 1955 to 2020 | no limit | 74 | 92% | 8.19 | 1,200 | 300 ug/L health guideline |
| Sodium 1955 to 2020 | no limit | 61 | 100% | 16.5 | 330 | 20 mg/L health guideline |
| Radon 2005 to 2020 | no limit | 23 | 96% | 269 | 1,280 | 2,000 pCi/L health guideline |
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Fluoride | 0%81 samples | n/a | 0%21 samples | n/a |
| Nitrate | 0%12 samples | n/a | 0%21 samples | n/a |
Fluoride has held within a few points between the two most recent periods with enough samples.
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among contaminants with a federal limit, no tested sample in Jefferson County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Jefferson County
- 1Coliform bacteriaRecommended for every private well, every year.
- 2RadonMedian local reading is 269 pCi/L.
- 3NitrateRecommended for every private well, especially near farms or septic systems.
- 4ChlorideDetected in 100% of local samples.
- 5IronDetected in 96% of local samples.
- 6FluorideDetected in 96% of local samples.
- 7ManganeseDetected in 92% of local samples.
- 8Volatile organic compounds (VOCs)17 hazardous waste sites on record locally.
- 9Metals panel17 hazardous waste sites on record locally.
Test your Jefferson County well for coliform bacteria, radon and nitrate
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in New York: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Jefferson County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Jefferson County
2,420 domestic wells in Jefferson County are on record with the state. the typical well is 105 feet deep (one in ten goes past 221 feet).
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open NYSDEC water well completion reports and choose Water Well.
- The report lists depth, depth to bedrock, cased depth, yield and the driller.
Drillers have filed reports with the state since April 2000; a well drilled before then usually has no record.
The rock under Jefferson County
New York and New England carbonate-rock aquifers
Carbonate-rock. Limestone and dolomite move water through cracks and solution channels, sometimes very fast. Bacteria and nitrate can travel from the surface to a well in days, so annual bacteria testing matters more here than most places; hardness is a given.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in New York
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Private Wells, NYSDOH
- Environmental Laboratory Approval Program, NYSDOH
Contamination sources on record in Jefferson County
NYSDEC remediation sites records 17 hazardous waste sites in Jefferson County, among 42 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 17
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 25
- other remediation projects
Treatment that fits the local profile
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Jefferson County
No water treatment company serves Jefferson County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Jefferson County, and you get an email naming it first.
Common questions
How deep are wells in Jefferson County?
The typical domestic well in Jefferson County is 105 feet deep, based on 2,420 wells reported to the state. One in ten is deeper than 221 feet.
Is there arsenic in well water in Jefferson County?
Arsenic was detected in 53% of 38 public well samples in Jefferson County, and 0% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Jefferson County?
The median radon level across 23 public samples in Jefferson County was 269 pCi/L, with a high of 1,280 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Jefferson County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Towns in Jefferson County
22 towns have fewer than 30 public samples and are included in the Jefferson County totals above rather than shown separately: Adams, Alexandria, Antwerp, Brownville, Cape Vincent, Champion, Clayton, Ellisburg, Henderson, Hounsfield, Lorraine, Lyme, Orleans, Pamelia, Philadelphia, Rodman, Rutland, Theresa, Watertown, Watertown, Wilna, Worth.
Counties near Jefferson County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the New York dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 707 samples in Jefferson County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 29,710 people on private wells in Jefferson County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- NYSDEC water well completion reports: 2,470 well records in Jefferson County, 2,420 domestic. Water well completion reports filed with the New York State Department of Environmental Conservation Water Well Contractor Program since 2000. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
- NYSDEC remediation sites: 42 regulated sites located in Jefferson County. State Superfund, brownfield, voluntary cleanup, RCRA and spill remediation sites from the New York State Department of Environmental Conservation Environmental Remediation Sites database. Retrieved September 16, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.