States › New York › Nassau County

Nassau County, NY Water Quality

Water quality data for 8 public water systems serving Nassau County, New York — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 8 water systems · 10 cities
✅
Generally Safe — Most Systems Performing Well

The majority of water systems have no active violations and lead levels well below the federal action level.

B

Nassau County Earns a B

Nassau County: 10 communities across 8 water systems. 100.0% have no open violations.

  • Median lead where detected: 1.60 ppb
  • 7 communities with a lead detection, 3 reporting none detected
  • 6 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 100.0% of communities have no open violations
1.6 ppb
Median Lead Level
County-wide, 90th percentile
8
Water Systems
Active CWS & NTNCWS
100%
Violation-Free
No active violations on record
How we grade counties: MyWaterIQ uses EPA SDWIS enforcement data — actual MCL violations and lead test results — not the aspirational MCLG targets used by some sites. A grade reflects real compliance history, not theoretical risk. Learn more →

Cities by Water Quality

⭐ Best Performing
  • Oyster Bay
    Not detected
    1 health-based violation since 2015
    A
  • Long Beach
    1.10 ppb
    1 health-based violation since 2015
    A
  • Old Westbury
    5.40 ppb
    Lead at 5.40 ppb, above a third of the action level
    A
  • Hempstead
    4.20 ppb
    3 health-based violations since 2015
    B
  • North Hempstead
    1.60 ppb
    PFAS above the limit at 1 of 9 sampling points
    B
⚠ Needs Attention
  • North Hempstead
    1.60 ppb
    PFAS above the limit at 1 of 9 sampling points
    B
  • Glen Cove
    3.90 ppb
    PFAS above the limit at 1 of 4 sampling points
    B
  • Floral Park
    1.40 ppb
    PFAS above the limit at 2 of 13 sampling points
    B
  • New Hyde Park
    1.40 ppb
    PFAS above the limit at 2 of 13 sampling points
    B
  • Greenvale
    Not detected
    PFAS above the limit at 1 of 8 sampling points
    B
County Lead Level — Median 1.6 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 1.6 ppb — 10.7% of the federal action level
Systems by Lead Level
Under 5 ppb
6
5 – 10 ppb
1
No Data
3

All Cities in Nassau County

Hempstead 4.20 ppb B
Oyster Bay Not detected A
Long Beach 1.10 ppb A
North Hempstead 1.60 ppb B
Glen Cove 3.90 ppb B
Floral Park 1.40 ppb B
New Hyde Park 1.40 ppb B
Old Westbury 5.40 ppb A
Greenvale Not detected B
Roslyn Harbor Not detected B
Showing 10 cities
No active violations Active violations

About Nassau County Drinking Water

Nassau County is served by 8 water systems covering 10 communities. No community here has an open violation on record.

Of the communities reporting lead results, 7 recorded a detection, with a median of 1.60 ppb — 11% of the federal action level. 3 reported none detected, which means below the laboratory limit rather than an absence of lead.

6 of 10 communities have PFAS above the limits EPA set in 2024, measured as a running annual average at each sampling point. State inspectors recorded no significant deficiencies.

Frequently Asked Questions

Is Nassau County tap water safe to drink?▼
No community in Nassau County has an open violation on record. 6 of 10 have PFAS above the federal limit, which is the main open concern.
What is the lead level in Nassau County?▼
Among communities with a detection the median is 1.60 ppb, 11% of the 15 ppb action level. 3 reported none detected and 0 reported no result.
How many water systems serve Nassau County?▼
8 community water systems serve 10 communities here.
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