347 public water systems in Ohio were sampled in EPA's UCMR 5 programme (2023–2025); we show six PFAS and lithium. Read 2026-10-31.
59 of 347 systems had at least one sample above a 2024 federal limit; 158 had at least one PFAS found above the reporting level; 189 had none found above the reporting level.
A single sample above a 2024 limit is a measurement, not a violation. Compliance is judged on running yearly averages, and water systems have until 2029 to meet the limits. On 20 May 2026 EPA proposed giving qualifying systems until 2031 for PFOA and PFOS and removing the limits for PFHxS, PFNA and HFPO-DA; those proposals were not final when we last checked (5 Nov 2026). Counts are per system, not per person; population figures are available only for systems serving more than 25,000 people (about 7,509,778 people across those systems here). UCMR 5 was a one-time national monitoring programme (2023–2025). The results are a snapshot at the system's entry points or taps on the sample dates, not a continuous measurement and not a compliance record.
| System | People served | UCMR 5 result |
|---|---|---|
| Columbus Columbus Public Water System | 1,309,468 | Above the 2024 limit in at least one sample |
| Cleveland Cleveland Public Water System | 1,308,955 | None detected (below the reporting level) |
| Cincinnati Cincinnati Public Water System | 800,000 | Above the 2024 limit in at least one sample |
| Toledo Toledo, City of | 360,000 | None detected (below the reporting level) |
Pages for these are being added in stages. The data for all 347 systems is in the public dataset.
| System | People served | UCMR 5 result |
|---|---|---|
| Akron City Pws Akron City Pws | 280,000 | Above the 2024 limit in at least one sample |
| Montgomery County Water Services 1 Pws Montgomery County Water Services 1 Pws | 150,207 | Above the 2024 limit in at least one sample |
| Del-Co Water Company, Inc. Del-Co Water Company, Inc. | 150,000 | Above the 2024 limit in at least one sample |
| Dayton Public Water System Dayton Public Water System | 141,407 | Above the 2024 limit in at least one sample |
| Clermont Public Water System Clermont Public Water System | 133,059 | Above the 2024 limit in at least one sample |
| Youngstown City Pws Youngstown City Pws | 130,530 | Above the 2024 limit in at least one sample |
| Butler Co. Water District 2 Pws Butler Co. Water District 2 Pws | 116,572 | Detected, below the 2024 limit |
| Canton Public Water System Canton Public Water System | 107,113 | None detected (below the reporting level) |
| Warren Co. Richard Renneker Pws Warren Co. Richard Renneker Pws | 99,000 | None detected (below the reporting level) |
| Aqua Ohio - Massillon Pws Aqua Ohio - Massillon Pws | 95,636 | None detected (below the reporting level) |
| Montgomery County Water Services 2 Pws Montgomery County Water Services 2 Pws | 83,033 | Above the 2024 limit in at least one sample |
| Lake County West Water Subdistrict Lake County West Water Subdistrict | 78,379 | None detected (below the reporting level) |
| Aqua Ohio - Mentor Aqua Ohio - Mentor | 74,500 | None detected (below the reporting level) |
| Rural Lorain Co. Water A Rural Lorain Co. Water A | 73,125 | None detected (below the reporting level) |
| Elyria Water Department Elyria Water Department | 68,000 | None detected (below the reporting level) |
| Lima City Lima City | 65,619 | None detected (below the reporting level) |
| Lorain City Pws Lorain City Pws | 64,152 | None detected (below the reporting level) |
| Hamilton Public Water System Hamilton Public Water System | 62,447 | Above the 2024 limit in at least one sample |
| Springfield City Pws Springfield City Pws | 60,680 | None detected (below the reporting level) |
| Aqua Ohio - Struthers Aqua Ohio - Struthers | 58,551 | None detected (below the reporting level) |
| Findlay City Findlay City | 54,040 | None detected (below the reporting level) |
| Middletown City Pws Middletown City Pws | 51,229 | Above the 2024 limit in at least one sample |
| Cuyahoga Falls City Pws Cuyahoga Falls City Pws | 51,114 | None detected (below the reporting level) |
| Mansfield City Mansfield City | 51,000 | None detected (below the reporting level) |
| Lakewood City Pws Lakewood City Pws | 50,942 | None detected (below the reporting level) |