waterbycounty
Compiled federal source snapshot

Ohio Water Quality

Drinking water data for all 88 counties.

Avg SDWIS Compliance Index

54.6

Most Common Five-Year SDWIS Compliance Band

B

Counties with Data

88

of 88 total

County water atlas

Ohio water signals by county

A state-level 2.5D view across drinking-water compliance, watershed impairment, monitoring density, and streamflow snapshot context. Pin any county, switch layers, then use the lens controls to compare index ranges, recorded violation rates, or impaired watersheds without leaving the page.

Counties

88

Avg SDWIS index

54.6

Watersheds

0

ATTAINS counties

Monitoring

88

76 fresh USGS snapshots

State atlas layers combine EPA SDWIS health-based violations, EPA ATTAINS 303(d) impairment assessments, EPA Water Quality Portal monitoring sites, and representative USGS NWIS streamflow gauges. Streamflow values appear only for fresh pipeline snapshots, not as a continuously updated stream. County pages include the observation time and year.

Prepared by ByCounty Editorial TeamPublished by WaterByCounty

Multi-source coverage in Ohio

Beyond Drinking Water

EPA SDWIS

88/ 88

counties with drinking-water compliance data

394 health violations statewide (5yr)

EPA ATTAINS

—

No §303(d) assessments yet for Ohio

EPA WQP

2,367

monitoring sites across 88 counties

517,601 total readings (5yr window)

USGS NWIS

76

counties with a fresh pipeline snapshot

1 above75 below

State atlas notes

What stands out in Ohio

County water quality is not one number. The strongest read comes from comparing drinking-water compliance against watershed impairment, monitoring density, and streamflow context. Use these signals as a starting point, then open any county profile for source-level detail.

Compliance spread

Butler County has the highest value in the published state SDWIS Compliance Index table at 86.2/100, while Henry County has the lowest at 7.8/100. That is a 78.4 point gap inside one state.

Zero health violations

13

3+ health violations

47

Monitoring hubs

Lucas County122 sitesErie County98 sitesAshtabula County85 sites

Lowest flow reads

Henry County0%Hardin County1%Lorain County2%

Highest fresh streamflow pipeline snapshots: Jefferson County (172%, observation 2026), Monroe County (83%, observation 2026), Medina County (82%, observation 2026). These are source-data observations, not household tap-water conclusions.

All Ohio Counties

CountySDWIS Compliance Index
Butler County86.2
Cuyahoga County86.2
Delaware County86.2
Erie County86.2
Gallia County86.2
Highland County86.2
Knox County86.2
Lake County86.2
Marion County86.2
Morrow County86.2
Pike County86.2
Scioto County86.2
Wyandot County86.2
Hamilton County71.9
Lucas County71.9
Clermont County71.2
Greene County70.7
Franklin County70.3
Montgomery County69.0
Mahoning County67.8
Lorain County67.4
Summit County66.9
Medina County66.3
Warren County66.1
Fairfield County65.6
Stark County65.6
Allen County64.8
Ashtabula County64.5
Licking County63.8
Wood County63.8
Ross County63.3
Miami County62.6
Tuscarawas County62.6
Lawrence County62.3
Sandusky County62.3
Columbiana County61.9
Shelby County61.9
Union County61.6
Ashland County60.7
Fayette County60.5
Trumbull County60.5
Mercer County59.6
Huron County59.1
Clinton County58.6
Washington County58.3
Champaign County57.6
Jackson County56.5
Brown County55.2
Adams County54.7
Auglaize County54.7
Coshocton County54.1
Portage County53.8
Ottawa County50.5
Williams County50.3
Madison County50.1
Belmont County49.5
Clark County47.9
Wayne County46.8
Guernsey County44.7
Preble County44.5
Crawford County44.2
Richland County44.2
Athens County42.8
Darke County42.6
Jefferson County42.6
Hancock County41.8
Pickaway County41.8
Meigs County41.1
Noble County41.1
Seneca County40.6
Muskingum County35.3
Geauga County34.0
Hardin County33.3
Monroe County32.0
Vinton County31.4
Logan County31.1
Hocking County30.0
Morgan County26.8
Putnam County26.4
Perry County24.9
Carroll County20.9
Van Wert County20.4
Holmes County17.9
Fulton County17.0
Harrison County13.8
Defiance County13.5
Paulding County13.0
Henry County7.8

Frequently Asked Questions

Which Ohio county has the highest SDWIS Compliance Index?
Butler County has the highest SDWIS Compliance Index in the published Ohio cohort at 86.2/100. This WaterByCounty relative comparison is not an EPA score and does not establish current conditions for a utility or address.
What does the Five-Year SDWIS Compliance Band mean?
The band is derived only from each county aggregation's recorded health-violation rate per 100,000 people served for the stated five-year source window. It is separate from the relative SDWIS Compliance Index and is not a current determination for a specific utility or address.
Which USGS streamflow records are shown across Ohio?
WaterByCounty has 76 fresh USGS pipeline snapshots in the published Ohio cohort. Each county page shows its observation timestamp and year. A pipeline snapshot is not a continuously updated reading or a tap-water safety measure.
Where can Ohio residents find current official information?
Review the applicable utility's Consumer Confidence Report, active notices, and the state drinking-water agency. WaterByCounty's county-level historical aggregations do not establish the current status of a specific utility, address, private well, or household plumbing system.
What does Water Quality Portal monitoring volume show in Ohio?
The published county records contain 517,601 results from 2,367 monitoring locations in the site's five-year aggregation. Monitoring volume does not by itself indicate better or worse water quality.

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. The WaterByCounty SDWIS Compliance Index reflects the recorded rate and is not an EPA score.

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.

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