Where does the tap water come from?

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.

1,233 of 1,233 ZIPs have data.

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Map of Ohio by Where the water comes from

Source

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

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Intakes and plantsViolationsDisinfection byproductsPFASLeadFluoride and treatmentAlgal toxinsGroundwaterAquiferSewage plantsStream healthWatershed

• Where Ohio's tap water comes from, ZIP by ZIP

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