Well water in Suffolk County, New York

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Testing strongly recommended

tested well samples in Suffolk County exceeded the EPA limit for PFOA (4 ng/L), based on public data from USGS Water Quality Portal.

72,929 test results across 15 contaminants from at least 1,635 wells, 1919 to 2025; iron has the most at 15,495. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 79,294 people in Suffolk County get their drinking water from a private well, per USGS 2015 county water use. That is about 5% of residents.

Separately, the USGS national arsenic model estimates that 9% of the 79,294 people on private wells in Suffolk County draw water above 10 ug/L (the model's range is 5% to 14%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Suffolk 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
PFOA 2018 to 2024	67%	60	72%	8.25	290	4 ng/L EPA limit
PFOS 2018 to 2024	43%	60	53%	1.45	260	4 ng/L EPA limit
Nitrate 1973 to 2024	7%	2,336	82%	0.825	40	10 mg/L EPA limit
E. coli 2007 to 2022	7%	46	7%	0	2	0 MPN/100mL EPA limit
Radium (226 + 228) 1973 to 2022	3%	58	69%	0.14	61	5 pCi/L EPA limit
Arsenic 1919 to 2022	2%	1,399	24%	0	38	10 ug/L EPA limit
Copper 1919 to 2022	1%	6,155	53%	0.001	31.2	1.3 mg/L EPA limit
Lead 1971 to 2022	<1%	2,093	24%	0	800	15 ug/L EPA limit
Fluoride 1934 to 2025	<1%	4,482	31%	0	48	4 mg/L EPA limit
Uranium 2006 to 2022	0%	71	32%	0	0.21	30 ug/L EPA limit
Iron 1919 to 2025	no limit	15,495	70%	40	440,000	300 ug/L nuisance level
Chloride 1919 to 2025	no limit	14,506	100%	10	19,900	250 mg/L nuisance level
Manganese 1919 to 2025	no limit	14,418	57%	0.3	190,000	300 ug/L health guideline
Sodium 1919 to 2025	no limit	11,724	100%	7.5	9,500	20 mg/L health guideline
Radon 2012 to 2016	no limit	26	100%	106	300	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
Copper	1%5,988 samples	0%55 samples	0%110 samples	n/a
Fluoride	<1%4,227 samples	0%103 samples	0%118 samples	3%34 samples
Nitrate	7%1,902 samples	2%154 samples	9%228 samples	12%52 samples
Lead	<1%2,004 samples	0%55 samples	0%32 samples	n/a
Arsenic	1%1,310 samples	4%55 samples	0%32 samples	n/a
Uranium	n/a	0%37 samples	0%32 samples	n/a

Copper, fluoride, nitrate, lead, arsenic, uranium have 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 address

What this means

The contaminants most often above their limit here are pfoa (67% of 60 samples), pfos (43% of 60 samples), and nitrate (7% of 2,336 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.

Iron, Chloride, 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 Suffolk County

1
PFOA
67% of 60 local samples were above the limit.
2
PFOS
43% of 60 local samples were above the limit.
3
Nitrate
7% of 2,336 local samples were above the limit.
4
E. coli
7% of 46 local samples were above the limit.
5
Radium (226 + 228)
3% of 58 local samples were above the limit.
6
Arsenic
2% of 1,399 local samples were above the limit.
7
Copper
1% of 6,155 local samples were above the limit.
8
Volatile organic compounds (VOCs)
248 hazardous waste sites on record locally.
9
Metals panel
248 hazardous waste sites on record locally.

Test your Suffolk County well for PFOA, PFOS 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 $209 Already 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 Suffolk County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Suffolk County

10,467 domestic wells in Suffolk County are on record with the state. the typical well is 70 feet deep (one in ten goes past 140 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.

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 Suffolk County

NYSDEC remediation sites records 248 hazardous waste sites in Suffolk County, among 316 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.

248: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
68: other remediation projects

Treatment that fits the local profile

PFOA

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

PFOS

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

E. coli

Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system

Radium (226 + 228)

Water softener (cation exchange); 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 PFOA

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For PFOA

Whole-house PFAS carbon system

whole-house, at the point of entry, about $3,000

Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.

For PFOA

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

For PFOS

Aquasana Claryum 3-Stage under-sink filter

under-sink or countertop, about $175

Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.

For PFOS

Aquasana HealthShield whole-house filter

whole-house, at the point of entry, about $2,099

Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.

For E. coli

UV disinfection system

whole-house, at the point of entry, about $900

Fix the well cap and casing first; UV keeps bacteria from returning.

For E. coli

Aquasana Rhino Well Water with UV

whole-house, at the point of entry, about $2,871

Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.

Free, no obligation

Get on the list for a free in-home water test in Suffolk County

No water treatment company serves Suffolk 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 Suffolk County, and you get an email naming it first.

Common questions

How deep are wells in Suffolk County?

The typical domestic well in Suffolk County is 70 feet deep, based on 10,467 wells reported to the state. One in ten is deeper than 140 feet.

Is there arsenic in well water in Suffolk County?

Arsenic was detected in 24% of 1,399 public well samples in Suffolk County, and 2% 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 Suffolk County?

The median radon level across 26 public samples in Suffolk County was 106 pCi/L, with a high of 300 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Suffolk 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 Suffolk County

2 towns have fewer than 30 public samples and are included in the Suffolk County totals above rather than shown separately: Poospatuck Reservation, Shinnecock Reservation.

Counties near Suffolk 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: 72,929 samples in Suffolk 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 79,294 people on private wells in Suffolk 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: 18,971 well records in Suffolk County, 10,467 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: 316 regulated sites located in Suffolk 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.