Well water in Nassau County, New York

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Testing strongly recommended

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

71,312 test results across 15 contaminants from at least 1,824 wells, 1903 to 2024; chloride has the most at 17,999. Data refreshed September 3, 2026.

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

What individual samples found

Each row summarizes every public sample for that contaminant inside Nassau 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 2022	56%	93	68%	8.1	49	4 ng/L EPA limit
PFOS 2018 to 2022	44%	93	57%	2.2	52	4 ng/L EPA limit
Nitrate 1948 to 2022	16%	2,225	90%	3.9	36	10 mg/L EPA limit
Lead 1971 to 2024	3%	1,834	40%	0	3,200	15 ug/L EPA limit
Arsenic 1971 to 2024	<1%	830	40%	0	64	10 ug/L EPA limit
Copper 1952 to 2024	<1%	2,888	84%	0.03	11.2	1.3 mg/L EPA limit
Fluoride 1934 to 2024	<1%	5,500	57%	0	10	4 mg/L EPA limit
Uranium 2006 to 2024	0%	23	30%	0	0.04	30 ug/L EPA limit
Radium (226 + 228) 2012 to 2022	0%	20	85%	0.42	2.2	5 pCi/L EPA limit
Chloride 1903 to 2024	no limit	17,999	100%	8.8	20,400	250 mg/L nuisance level
Iron 1935 to 2024	no limit	15,238	90%	130	869,000	300 ug/L nuisance level
Manganese 1949 to 2024	no limit	14,175	71%	0	21,500	300 ug/L health guideline
Sodium 1934 to 2024	no limit	10,377	99%	8.6	50,800	20 mg/L health guideline

Sampled fewer than 10 times, too few to summarize: E. coli (8), Radon (9).

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	<1%5,408 samples	0%24 samples	0%54 samples	0%14 samples
Copper	<1%2,829 samples	0%24 samples	0%33 samples	n/a
Nitrate	16%2,139 samples	0%39 samples	0%46 samples	n/a
Lead	3%1,795 samples	0%24 samples	0%13 samples	n/a
Arsenic	<1%789 samples	4%24 samples	7%15 samples	n/a
PFOA	n/a	n/a	92%25 samples	43%68 samples

PFOA above the limit in Nassau County fell from 92% of 25 samples in the 2010s to 43% of 68 in the 2020s.

Fluoride, copper, nitrate, lead, arsenic 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 (56% of 93 samples), pfos (44% of 93 samples), and nitrate (16% of 2,225 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.

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 Nassau County

1
PFOA
56% of 93 local samples were above the limit.
2
PFOS
44% of 93 local samples were above the limit.
3
Nitrate
16% of 2,225 local samples were above the limit.
4
Lead
3% of 1,834 local samples were above the limit.
5
Arsenic
<1% of 830 local samples were above the limit.
6
Copper
<1% of 2,888 local samples were above the limit.
7
Fluoride
<1% of 5,500 local samples were above the limit.
8
Volatile organic compounds (VOCs)
221 hazardous waste sites on record locally.
9
Metals panel
221 hazardous waste sites on record locally.

Test your Nassau 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 Nassau County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Nassau County

138 domestic wells in Nassau County are on record with the state. the typical well is 158 feet deep (one in ten goes past 430 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 Nassau County

Northern Atlantic Coastal Plain aquifer system

Semiconsolidated sand. Coastal plain sands like these give steady yields at moderate depth. Salt water and sodium are the usual issues near the coast, and nitrate where the water table is shallow; arsenic and radon from bedrock are less common.

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 Nassau County

NYSDEC remediation sites records 221 hazardous waste sites in Nassau County, among 350 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.

221: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
129: 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

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

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 lead

Acid neutralizing filter

whole-house, at the point of entry, about $1,200

Raises pH so plumbing stops leaching lead and copper.

Free, no obligation

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

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

Common questions

How deep are wells in Nassau County?

The typical domestic well in Nassau County is 158 feet deep, based on 138 wells reported to the state. One in ten is deeper than 430 feet.

Is there arsenic in well water in Nassau County?

Arsenic was detected in 40% of 830 public well samples in Nassau County, and <1% 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 often should I test a private well in Nassau 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 Nassau County

Counties near Nassau 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: 71,312 samples in Nassau 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.
NYSDEC water well completion reports: 1,173 well records in Nassau County, 138 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: 350 regulated sites located in Nassau 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.