Story · Water
Where Ohio's tap water comes from
Every Ohio ZIP code, colored by the kind of source its tap water comes from.
Every Ohio ZIP code's tap water traces back to one of five kinds of source: Lake Erie, the Ohio River, an inland river or stream, a reservoir built to store one, or groundwater pumped from wells. Which one a place has depends on where a utility found a reliable supply, sometimes a century ago, and how far its pipes now reach.
This is a tour of that pattern rather than a ranking: how many Ohioans' taps trace to each class of source, and where each one is most common, drawn from the same source classification that colors the map. Every water system's own page carries the EPA and Ohio EPA records behind it.
Across the state
One dot per ZIP code, colored the way the map colors this topic; larger dots are more populous ZIP codes.
Five kinds of source
Residents on a community water system, by the kind of source their utility treats: 10,455,183 people in all.
Lake Erie
2,727,890 residents (26% of Ohioans on a community system) across 124 ZIP codes. Most common around Cleveland, Toledo, Lorain, Sandusky, Lake & Ashtabula counties.
The largest utilities treating this kind of source (20 producers in all):
- Cleveland Public Water SystemLake Erie1,308,955 served
- Toledo City OfLake Erie360,000 served
- Lake County West Water SubdistrictLake Erie78,379 served
- Aqua Ohio - MentorLake Erie74,500 served
- Elyria Water DepartmentLake Erie68,000 served
Ohio River
1,019,659 residents (10% of Ohioans on a community system) across 55 ZIP codes. Most common around Cincinnati, Portsmouth, Steubenville, East Liverpool.
The largest utilities treating this kind of source (8 producers in all):
- Cincinnati Public Water SystemOhio River (Miller Plant, ~88%) plus Great Miami Buried Valley Aquifer wells (~12%)750,200 served
- West Virginia American Water - HuntingtonOhio River (with Guyandotte River backup intake)98,647 served
- Portsmouth CityOhio River40,475 served
- Steubenville, City OfOhio River17,000 served
- East Liverpool CityOhio River12,586 served
Inland rivers
2,224,906 residents (21% of Ohioans on a community system) across 63 ZIP codes. Most common around Scioto, Maumee, Great Miami, Olentangy, Sandusky….
The largest utilities treating this kind of source (41 producers in all):
- Columbus Public Water SystemScioto River (Griggs & O'Shaughnessy), Hoover Reservoir on Big Walnut Ck, plus wells1,305,946 served
- Del-co Water Company, Inc.Olentangy River, O'Shaughnessy and Alum Creek reservoirs, plus Knox County wells150,000 served
- Lima CityAuglaize River and Ottawa River, stored in city upground reservoirs65,619 served
- Newark CityNorth Fork Licking River49,934 served
- Aqua Pennsylvania - Shenango Valley (Sharon, PA)Shenango River / Shenango River Lake (Pymatuning area) surface intake48,000 served
Reservoirs & inland lakes
1,125,163 residents (11% of Ohioans on a community system) across 99 ZIP codes. Most common around Hoover (Columbus north), Lake Rockwell, Meander, Mosquito, Alum Creek….
The largest utilities treating this kind of source (30 producers in all):
- Akron CityLake Rockwell (Cuyahoga River impoundment)280,000 served
- Clermont Public Water SystemWilliam H. Harsha Lake plus wells in the Little Miami River and Ohio River aquifers133,059 served
- Aqua Ohio - StruthersEvans Lake (Yellow Creek impoundment)58,551 served
- Findlay CityFindlay's two upground reservoirs, filled by pumping from the Blanchard River54,040 served
- Mansfield CityClear Fork Reservoir (Clear Fork of the Mohican River), plus 9 city wells51,000 served
Groundwater (wells)
3,357,565 residents (32% of Ohioans on a community system) across 332 ZIP codes. Most common around Dayton, Canton, Massillon, Springfield, Hamilton, Zanesville….
The largest utilities treating this kind of source (747 producers in all):
- Dayton Public Water SystemGreat Miami Buried Valley Aquifer wells (recharged by Great Miami & Mad Rivers)141,407 served
- Canton Public Water SystemGlacial sand-and-gravel aquifer (3 well fields)107,113 served
- Aqua Ohio - MassillonWells in Tuscarawas Valley sand & gravel aquifer95,636 served
- Warren CountyWells in the Little Miami and Great Miami river valley aquifers81,975 served
- Hamilton Public Water SystemGreat Miami Buried Valley Aquifer (wells)62,447 served
How this was measured
Each ZIP is colored by the community water system that serves the most of its residents (2020 census block populations against EPA service areas), traced through any wholesale purchases to the utility that actually treats the water. A ZIP is hatched only when more than half of its residents live outside every mapped system, which in Ohio means private wells.
Every ZIP code's own page carries the full detail behind its figure, and the Where the water comes from topic page ranks the whole state.
Sources
U.S. EPA SDWIS and Community Water System Service Area Boundaries (v3, 2026), Ohio EPA primacy data, 2020 census blocks: the system serving most residents, traced through purchases to the treating utility; Ohio EPA 2023 Sewer and Water Rate Survey (Ohio State, May 2025) for household bills; Ohio EPA DEFA loan awards since 2016 for the loans paragraph.
EPA SDWIS · EPA service area boundaries · Ohio EPA drinking water · Ohio EPA rate survey
The figures behind this page are open data: the open JSON, CC BY 4.0 for the compilation. Report a correction.
Cite this page
Cite this page as:
Ohio Hometown Atlas (Open Shower Co), "Where Ohio's tap water comes from", https://hometownatlas.openshowerco.com/stories/where-ohios-tap-water-comes-from/, built 2026-09-15, accessed [date].
One figure from it:
Ohio Hometown Atlas (Open Shower Co), "Where Ohio's tap water comes from", https://hometownatlas.openshowerco.com/stories/where-ohios-tap-water-comes-from/, built 2026-09-15, accessed [date]; Where the water comes from from EPA SDWIS.
How to cite · Report a correction · Built 2026-09-15