waterbycounty
EPA SDWIS

Suffolk County Water Quality

Suffolk County, New York

Water Grade

A

Water Score

71.3

Violations

5

State Rank

#3

of 57 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

A

Based on EPA compliance history and violation data

Water Score

71.3/100

Higher = better quality

Health Violations

5

Health-based violations

Violation Rate

0.4%

Systems with violations

Water Advisory: Suffolk County

Water Verdict

Suffolk County receives a good water quality assessment with a grade of A and a score of 71.3 out of 100. While the water supply is generally safe, occasional monitoring gaps or minor contaminant detections may occur.

Violation Context

Suffolk County has recorded 5 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 0.4 violations per 1,000 residents, this rate is relatively low compared to many U.S. counties.

Consumer Guidance

Tap water in Suffolk County is generally safe to drink based on available data. Residents should still review their utility's annual Consumer Confidence Report for transparency on detected contaminants. With 5 recorded health violations, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Suffolk County has better water quality than the average county in New York. Its water score is 31.2 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Past 5 years

Water Quality Monitoring

Monitoring Sites

450

Active in the past 5 years

Measurements Recorded

72K

71,718 total readings

Most Measured

  • Physical
  • Microbiological
  • Organics, Pesticide

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

16.7cfs

May 14, 7:00 PM UTC

vs Long-Term Average

46%

Well below typical

Primary Streamgage

PECONIC RIVER AT RIVERHEAD NY

USGS site
01304500
Drainage area
74.7 sq mi
Long-term mean
36.4 cfs

One representative streamgage (the one with the largest drainage area in the county). Many counties have multiple gauges — this view summarizes the primary one. The long-term mean is the full-record annual average; "% of typical" compares the latest reading against that average.

Improve your water quality at home

Berkey filters remove 99.9%+ of contaminants from tap water.

Shop Berkey →

Sponsored

Test your tap water

Tap Score provides professional mail-in water testing.

Get Tested →

Frequently Asked Questions

What is the water quality in Suffolk County, New York?
Suffolk County, New York has a drinking-water quality grade of A with a score of 71.3/100, based on EPA SDWIS compliance data. The county has 5 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Suffolk County?
Suffolk County has 5 health-based drinking water violations recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.
How much water-quality monitoring happens in Suffolk County?
EPA's Water Quality Portal records 71,718 measurements from 450 monitoring sites in Suffolk County over the past five years. The most frequently measured characteristic groups are Physical, Microbiological, Organics, Pesticide. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
What's happening with rivers in Suffolk County right now?
Suffolk County's primary USGS streamgage on the PECONIC RIVER is currently reading 16.7 cubic feet per second — 46% of the long-term mean of 36.36 cfs. This is well below typical — often a signal of drought stress on source water. For genuine real-time data, visit waterdata.usgs.gov.
How does Suffolk County water compare to the New York average?
Suffolk County's SDWIS water quality score of 71.3/100 is higher than the New York state average of 40.1. The average water quality grade across New York is D, based on data from 57 counties with available SDWIS data.
Is tap water safe to drink in Suffolk County?
Based on EPA SDWIS data, Suffolk County has a water quality grade of A (71.3/100). This indicates good to excellent water quality with strong SDWIS compliance. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Does Suffolk County have clean drinking water?
Suffolk County has 5 health-based drinking water violations according to EPA records. With a water quality score of 71.3/100 and grade A, the county's drinking water has had some compliance issues but continues to be monitored. Note: drinking-water compliance speaks to the public water system, not necessarily to the watershed itself — check the Watershed Health zone for ATTAINS §303(d) data.
How does Suffolk County rank for water quality in New York?
Suffolk County ranks #3 out of 57 counties in New York by SDWIS water quality score (1 = best). With a score of 71.3/100, it falls in the top third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Niagara County

New York

A

71.3

Water score

Chemung County

New York

B

69.5

Water score

Nassau County

New York

B

68.8

Water score

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP) — federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Live streamflow from the USGS National Water Information System (NWIS) — continuous discharge measurements from the largest-drainage gauge in each county, compared against the full-record long-term annual mean.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

By Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

Explore more data for Suffolk County

Property TaxCost of LivingCrime RateIncomeHealthSchoolsDisaster RiskWeatherCounty Score