waterbycounty
EPA SDWIS

Union County Water Quality

Union County, Ohio

Water Grade

B

Water Score

65.0

Violations

1

State Rank

#32

of 88 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

B

Based on EPA compliance history and violation data

Water Score

65/100

Higher = better quality

Health Violations

1

Health-based violations

Violation Rate

3.5%

Systems with violations

Water Advisory: Union County

Water Verdict

Union County receives a fair water quality assessment with a grade of B and a score of 65.0 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring.

Violation Context

Union County has recorded 1 health-based violation, meaning the water system experienced at least one exceedance of federal contaminant limits or treatment requirements. At 3.5 violations per 1,000 residents, this rate is moderate and suggests recurring water quality challenges.

Consumer Guidance

Tap water in Union 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 1 recorded health violation, 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

Union County has better water quality than the average county in Ohio. Its water score is 8.8 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

0.0%

0 of 3 assessed

Mostly healthy

Top Impairment Causes

No specific impairment causes reported for this county's assessed water bodies.

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

27

Active in the past 5 years

Measurements Recorded

6.0K

6,000 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

14.5cfs

May 14, 6:45 PM UTC

vs Long-Term Average

21%

Well below typical

Primary Streamgage

Mill Creek above Marysville OH

USGS site
03219781
Drainage area
74.1 sq mi
Long-term mean
68.5 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 Union County, Ohio?
Union County, Ohio has a drinking-water quality grade of B with a score of 65.0/100, based on EPA SDWIS compliance data. The county has 1 health-based drinking water violation over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Union County?
Union County has 1 health-based drinking water violation 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 Union County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 0.0% of Union County's 3 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 Union County?
EPA's Water Quality Portal records 6,000 measurements from 27 monitoring sites in Union 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 Union County right now?
Union County's primary USGS streamgage on the Mill Creek above Marysville OH is currently reading 14.5 cubic feet per second — 21% of the long-term mean of 68.53 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 Union County water compare to the Ohio average?
Union County's SDWIS water quality score of 65.0/100 is higher than the Ohio state average of 56.2. The average water quality grade across Ohio is D, based on data from 88 counties with available SDWIS data.
Is tap water safe to drink in Union County?
Based on EPA SDWIS data, Union County has a water quality grade of B (65.0/100). 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 Union County have clean drinking water?
Union County has 1 health-based drinking water violation according to EPA records. With a water quality score of 65.0/100 and grade B, 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 Union County rank for water quality in Ohio?
Union County ranks #32 out of 88 counties in Ohio by SDWIS water quality score (1 = best). With a score of 65.0/100, 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

Columbiana County

Ohio

B

65.1

Water score

Sandusky County

Ohio

B

65.3

Water score

Warren County

Ohio

B

64.5

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

Explore more data for Union County

Property TaxCost of LivingCrime RateIncomeHealthSchoolsDisaster RiskWeatherCounty Score