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Federal water data

County water report

Chester County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Chester County, Pennsylvania.

Water grade

F

Water score

38.4

State rank

#36

of 67

Health violations

93

EPA SDWIS, 5-year lookback

Watershed impaired

0.0%

41,870 water bodies assessed

Monitoring sites

177

33,600 recent measurements

Live streamflow

38%

East Branch Brandywine Creek below Downingtown, PA

Water at a glance

Key Water Indicators for Chester County

EPA SDWIS

Safety Grade

F

Score: 38.4 / 100

EPA SDWIS

Active Violations

93

5-year health-based lookback

EPA ATTAINS

Watershed Health

0% impaired

41,870 bodies assessed

USGS NWIS

Streamflow Snapshot

38% of mean

East Branch Brandywine Creek below Downingtown, PA

EPA WQP

Monitoring Sites

177

33,600 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

F

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

38.4/100

Health violations

93

Health-based violations

Violations per 100K served

36.1

Population-normalized SDWIS rate

Editorial analysis

Understanding Chester County’s Water

Drinking Water Quality Overview

EPA SDWIS

Chester County's water systems carry a failing grade, scoring 38.4 out of 100. Over the past five years, EPA SDWIS records 93 health-based violations — a pattern that public water utilities are required to disclose and correct.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). None of the assessed waterways are listed as impaired (0 of 41,870 water bodies) across Chester County's watersheds. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T15:00:00.000-04:00) puts East Branch Brandywine Creek below Downingtown, PA at 57.7 cfs — well below its long-term average at 38% 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. Chester County has extensive coverage with 177 active monitoring sites with 33,600 recent measurements on record. Predominant monitoring categories include physical and inorganics, minor, metals. 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 Chester County

Water Verdict

Chester County receives a poor water quality assessment with a grade of F and a score of 38.4 out of 100. The water supply has documented quality issues. Residents are strongly encouraged to use filtered or bottled water for drinking and to stay informed about utility improvement plans.

Violation Context

Chester County has recorded 93 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 36.1 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Chester County has a Grade F compliance record with 93 health-based violations — among the highest levels in the country. Chester County's drinking-water compliance score is 38.4 out of 100. The violation rate for Chester County is 36.1 per 100,000 people served. Residents are strongly advised to use a certified NSF 58 reverse-osmosis filter or bottled water for all drinking and cooking until violations are corrected. Contacting the Pennsylvania Department of Environmental Quality or Health can expedite utility compliance action. With 177 active water-quality monitoring sites in Chester County, data coverage is strong. A pipeline streamflow snapshot from the East Branch Brandywine Creek below Downingtown, PA gauge is also available on this page.

Regional Context

Chester County has water quality close to the average county in Pennsylvania. Its water score is within 0.5 points of the state average, meaning its overall water system performance is broadly representative of Pennsylvania as a whole.

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 Chester County's water environment

Official EPA Resources for Chester County

EPA How's My Waterway

Interactive watershed health data for Chester County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Chester County

Consumer Confidence Reports (PA)

Annual water quality reports from utilities in Pennsylvania

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

0.0%

0 of 41,870 assessed

Mostly healthy

Top Impairment Causes

No specific impairment causes reported for the assessed water bodies in this county.

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state; counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

177

Active in the past 5 years

Measurements Recorded

34K

33,600 total readings

Most Measured

  • Physical
  • Inorganics, Minor, Metals
  • Nutrient

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

57.7cfs

May 14, 7:00 PM UTC

vs Long-Term Average

38%

Well below typical

Primary Streamgage

East Branch Brandywine Creek below Downingtown, PA

USGS site
01480870
Drainage area
89.9 sq mi
Long-term mean
151 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.

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Water Cost Estimate

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Chester 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.

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Frequently Asked Questions

What is the water quality in Chester County, Pennsylvania?
Chester County, Pennsylvania has a drinking-water quality grade of F with a score of 38.4/100, based on EPA SDWIS compliance data. The county has 93 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 Chester County?
Chester County has 93 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 healthy are the watersheds in Chester County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 0.0% of Chester County's 41,870 assessed water bodies are classified as impaired (0 impaired). Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in Chester County?
EPA's Water Quality Portal records 33,600 measurements from 177 monitoring sites in Chester County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Minor, Metals, Nutrient. 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 Chester County right now?
Chester County's primary USGS streamgage on the East Branch Brandywine Creek below Downingtown, PA has a pipeline snapshot of 57.7 cubic feet per second — 38% of the long-term mean of 151.21 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 Chester County water compare to the Pennsylvania average?
Chester County's SDWIS water quality score of 38.4/100 is lower than the Pennsylvania state average of 38.9. The average water quality grade across Pennsylvania is F, based on data from 67 counties with available SDWIS data.
Is tap water safe to drink in Chester County?
Based on EPA SDWIS data, Chester County has a water quality grade of F (38.4/100). This indicates below-average compliance with significant violations. Residents may want to consider home water filtration or independent testing. 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).
Why does Chester County have so many water violations?
Chester County has 93 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.
How does Chester County rank for water quality in Pennsylvania?
Chester County ranks #36 out of 67 counties in Pennsylvania by SDWIS water quality score (1 = best). With a score of 38.4/100, it falls in the middle 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

Franklin County

Pennsylvania

F

40.2

Water score

Adams County

Pennsylvania

D

41.8

Water score

Schuylkill County

Pennsylvania

D

41.9

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.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments, state-reported and EPA-finalized.

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 Reviewed by Evan Brooks, Data Editor

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