County water report

Suffolk County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Suffolk County, New York.

Water grade

Water score

71.3

State rank

of 57

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

450

71,718 recent measurements

Live streamflow

46%

PECONIC RIVER AT RIVERHEAD NY

Water at a glance

Key Water Indicators for Suffolk County

EPA SDWIS

Safety Grade

Score: 71.3 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

46% of mean

PECONIC RIVER AT RIVERHEAD NY

EPA WQP

Monitoring Sites

450

71,718 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

71.3/100

Health violations

Health-based violations

Violations per 100K served

0.4

Population-normalized SDWIS rate

Data center water stress

Suffolk County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #997 nationally by combining its water score with mapped data center density.

DCWSI

42.8

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+21.3

Compared with US county median

Mapped facilities

Cable & Wireless Cable Landing Station
Shirley
OSM

See the Suffolk County data-center report Review methodology

Data Center Water Budget Calculator

Estimate daily water use for a hypothetical facility in Suffolk County.

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayModerate Impact

Your facility would use 14.9% of this county's industrial water baseline — manageable but worth monitoring against drought trends.

14.9% of county industrial baseline4.55 Mgal/day remaining headroom

Based on USGS 2020 water-use data and EPA-standard cooling intensity constants. Not a substitute for site-specific water rights analysis.

Editorial analysis

Understanding Suffolk County’s Water

Drinking Water Quality Overview

EPA SDWIS

Suffolk County earns an A grade for drinking water quality, scoring 71.3 out of 100. Over the past five years, EPA SDWIS records 5 health-based violations — a pattern that public water utilities are required to disclose and correct.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T14:00:00.000-05:00) puts PECONIC RIVER at 16.7 cfs — well below its long-term average at 46% of mean — low-flow conditions worth noting for water-dependent ecosystems. Streamflow is a leading indicator of drought stress, sediment load, and dilution capacity: low flows concentrate pollutants and warm water temperatures, stressing aquatic life and, in surface-water-dependent systems, the source water quality for treatment plants.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Suffolk County has extensive coverage with 450 active monitoring sites with 71,718 recent measurements on record. Predominant monitoring categories include physical and microbiological. More monitoring sites generally indicate greater scientific attention to local water conditions — and provide the baseline data that regulators use to set future impairment listings.

Editorial advisory

What the data suggests for 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 100,000 people served, this rate is relatively low compared to many U.S. counties.

Consumer Guidance

Tap water compliance data for Suffolk County shows a A grade. Suffolk County's drinking-water compliance score is 71.3 out of 100. Reviewing your utility's most recent Consumer Confidence Report provides the most accurate picture of detected contaminants and treatment status. An NSF-certified water filter can add an extra layer of safety for any household concerns. A pipeline streamflow snapshot from the PECONIC RIVER gauge is also available on this page.

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.

Advisory text summarizes county-level public records and is not a replacement for your utility's current Consumer Confidence Report or direct local notices.

Contaminants & Resources

Key issues flagged in Suffolk County's water environment

Official EPA Resources for Suffolk County

EPA How's My Waterway

Interactive watershed health data for Suffolk County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Suffolk County

Consumer Confidence Reports (NY)

Annual water quality reports from utilities in New York

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; the percent-of-typical value compares the latest reading against that average.

Free tool

Estimate Your Water Costs

Water Cost Estimate

Household size

3 people · ~225 gal/day

Filter type

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Suffolk County:C — Moderate

Some violations or watershed impairment detected.

Estimates use the national average residential water rate ($0.0068/gal, EPA/AWWA 2023) and EPA WaterSense per-person consumption baseline (75 gal/person/day). Actual bills vary by utility, usage tier, and local infrastructure fees. For informational purposes only.

Try the full calculator →

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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 streamflow snapshots 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 has a pipeline snapshot of 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 the latest gauge feed, 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

71.3

Water score

Chemung County

New York

69.5

Water score

Nassau County

New York

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 Evan Brooks, Data EditorUpdated May 14, 2026Reviewed by Evan Brooks, Data Editor

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