Nassau County, New York has about 1,392,438 residents (Census 2024 estimate) and 40 community water systems in EPA records. The largest local system is Liberty Utilities New York - Lynbrook, serving about 220,000 people from groundwater.
! 3 of 6 largest systems with health-based violationsPFAS detected at 5 of 6 sampled systemsHardness 1.6 gpg (low confidence)
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
How hard is Nassau County water?
Liberty Utilities New York - LynbrookEstimate: untreated local water, not your tap · Low confidence
1.6 gpg(28 mg/L), soft
Nassau County: median of 16,573 results from 1685 monitoring sites (streams and wells). Utilities may blend or treat water, so your tap can differ.
County estimates: Hard Water Map (hardwatermap.com), CC BY 4.0, derived from the USGS/EPA Water Quality Portal; file generated 2026-07-22. License
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
Softener size at 1.6 gpg
For a 3-person home using 57 gallons per person per day and regenerating weekly, you'd remove about 1,915 grains between regenerations. Suggested size: 24,000 grain. This uses a low-confidence county estimate, so confirm with a test first.
Estimate only. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
The 6 biggest of 40 community water systems on EPA records for this county. Service areas don't follow county lines; your water bill names your provider.
Liberty Utilities New York - Lynbrook
NY2902835 · serves about 220,000 people · Groundwater
Lead 90th percentile: 5 ppb (period starting 2026-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFHxS: highest sample 6.3 ppt (2 of 35 samples); federal limit 10.0 ppt as a running annual average, also counted in EPA's PFAS mixture (hazard index) limit (currently in effect; EPA has proposed removing it)
PFOS: highest sample 5.1 ppt (1 of 35 samples); federal limit 4.0 ppt as a running annual average
PFNA: highest sample 4.1 ppt (1 of 35 samples); federal limit 10.0 ppt as a running annual average, also counted in EPA's PFAS mixture (hazard index) limit (currently in effect; EPA has proposed removing it)
NY2902840 · serves about 135,000 people · Groundwater
! 3 health-based violations✓ Lead below detection✓ No PFAS detected
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2025-07-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
NY2902830 · serves about 120,000 people · Groundwater
✓ No health-based violations✓ Lead below action levelPFAS detected (8 types)
Lead 90th percentile: 1.4 ppb (period starting 2022-01-01) Older result. Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFOA: highest sample 10 ppt (5 of 26 samples); federal limit 4.0 ppt as a running annual average
PFPeA: highest sample 9.5 ppt (6 of 26 samples); no federal limit
PFHxA: highest sample 7.4 ppt (6 of 26 samples); no federal limit
PFBA: highest sample 7.1 ppt (4 of 26 samples); no federal limit
PFOS: highest sample 6.1 ppt (2 of 26 samples); federal limit 4.0 ppt as a running annual average
PFHxS: highest sample 4.5 ppt (2 of 26 samples); federal limit 10.0 ppt as a running annual average, also counted in EPA's PFAS mixture (hazard index) limit (currently in effect; EPA has proposed removing it)
PFBS: highest sample 3.6 ppt (3 of 26 samples); no individual limit; counted in EPA's PFAS mixture (hazard index) limit
PFHpA: highest sample 3.4 ppt (5 of 26 samples); no federal limit
NY2902827 · serves about 56,000 people · Groundwater
✓ No health-based violations✓ Lead below detectionPFAS detected (1 type)
Lead 90th percentile: <DL (below the lab detection/reporting limit; reported as 0) (period starting 2025-07-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFOS: highest sample 4.7 ppt (1 of 4 samples); federal limit 4.0 ppt as a running annual average
Public-record figures, not a test of your tap. Not 100% accurate or guaranteed. Confirm with a water test, your utility or a qualified pro before you buy or act.
A PFAS detection is not a violation. Federal limits (4 ppt for PFOA and PFOS) apply to running annual averages, with compliance required by 2029. In May 2026 EPA proposed extending the PFOA/PFOS deadline to 2031 and removing other PFAS limits; not final as of 2026-10-21.
Test your own tap
These are public records for whole systems. Your home's pipes, fixtures and any private well can change what you drink. A certified lab test or a hardness test strip gives you your own numbers. Then use our PFAS and lead filter selector to see which certifications to look for.
Common questions about Nassau County water
Is tap water in Nassau County safe to drink?
3 of the 6 largest systems here have at least one health-based violation in EPA records since October 2021 (see each system below for status). Liberty Utilities New York - Lynbrook's most recent lead 90th percentile was 5 ppb (2026), below the 15 ppb action level. Public records can't guarantee what comes out of your tap, especially with older plumbing, so a home test is the surest check.
How hard is the water in Nassau County?
There's no published utility figure in our data, but untreated local stream and well samples in Nassau County have a median of about 1.6 grains per gallon (28 mg/L, soft). That's a low-confidence estimate of source water, not your tap, so test before you buy equipment. For a 3-person home at 1.6 gpg, our softener calculator suggests a 24,000 grain unit as a starting point.
Is there PFAS in Nassau County water?
5 of the 6 sampled systems listed here detected at least one PFAS in EPA's UCMR 5 testing, and 4 results were above the level of a federal limit in at least one sample. A detection isn't a violation: federal PFAS limits apply to running annual averages starting in 2029.
Which water system serves my address in Nassau County?
Most homes are served by Liberty Utilities New York - Lynbrook or one of the other systems listed on this page, but service areas don't follow county lines. Your water bill names your provider, and its annual Consumer Confidence Report has the full test results.
Data as of October 21, 2026. Figures are copied from public records and combined with our own calculations; they can be out of date or wrong. Tapped Out isn't affiliated with any utility or the EPA. Written and reviewed by the Tapped Out team. How we calculate · All sources.