Suffolk County, New York has about 1,535,909 residents (Census 2024 estimate) and 26 community water systems in EPA records. The largest local system is Suffolk County Water Authority, serving about 1,100,000 people from groundwater.
! 1 of 6 largest systems with health-based violationsPFAS detected at 4 of 6 sampled systemsHardness 0–212 mg/L, varies by area
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 Suffolk County water?
Suffolk County Water AuthorityMeasured (utility report, 2025) · High confidence
0–212 mg/L(varies by area; no single average published)
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.
At this hardness most homes don't need a softener. Confirm with a test strip if you see scale.
Largest water systems in Suffolk County
The 6 biggest of 26 community water systems on EPA records for this county. Service areas don't follow county lines; your water bill names your provider.
Suffolk County Water Authority
NY5110526 · serves about 1,100,000 people · Groundwater
✓ No health-based violations✓ Lead below action levelPFAS detected (10 types)
Lead 90th percentile: 1.2 ppb (period starting 2025-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
PFHxA: highest sample 43.5 ppt (45 of 480 samples); no federal limit
PFPeA: highest sample 39.4 ppt (53 of 480 samples); no federal limit
6:2 FTS: highest sample 23.6 ppt (2 of 480 samples); no federal limit
PFOS: highest sample 17.4 ppt (13 of 480 samples); federal limit 4.0 ppt as a running annual average
PFBA: highest sample 12.6 ppt (9 of 480 samples); no federal limit
PFHxS: highest sample 10.8 ppt (19 of 480 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)
PFHpA: highest sample 9.6 ppt (4 of 480 samples); no federal limit
PFOA: highest sample 6.5 ppt (19 of 480 samples); federal limit 4.0 ppt as a running annual average
PFNA: highest sample 5.7 ppt (2 of 480 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 5.2 ppt (5 of 480 samples); no individual limit; counted in EPA's PFAS mixture (hazard index) limit
NY5103271 · serves about 42,000 people · Groundwater
✓ No health-based violations✓ Lead below action levelPFAS detected (3 types)
Lead 90th percentile: 1 ppb (period starting 2025-01-01). Action level: 15 ppb (drops to 10 ppb on Nov 1, 2027).
6:2 FTS: highest sample 11 ppt (1 of 24 samples); no federal limit
PFPeA: highest sample 3.3 ppt (2 of 24 samples); no federal limit
PFHxS: highest sample 3.2 ppt (1 of 24 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)
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 Suffolk County water
Is tap water in Suffolk County safe to drink?
1 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). Suffolk County Water Authority's most recent lead 90th percentile was 1.2 ppb (2025), 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 Suffolk County?
Suffolk County Water Authority reports hardness from 0 to 212 mg/L depending on where you live, with no single system-wide average, so check your area in its report or test your water.
Is there PFAS in Suffolk County water?
4 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 Suffolk County?
Most homes are served by Suffolk County Water Authority 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.