TTHM (Total Trihalomethanes) violations in Ohio
102 active public water systems in Ohio had a TTHM (Total Trihalomethanes) violation in the past three years, 6 of them in the latest quarter of EPA's data. What TTHM (Total Trihalomethanes) is and why it matters.
Systems with a TTHM (Total Trihalomethanes) violation
Latest quarter first, then largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Van Wert City Van Wert County |
10,846 | 4 | 0 | |
|
Nelsonville PWS Athens County |
6,656 | 4 | 3 | |
|
Maysville Regional Water Muskingum County |
6,540 | 3 | 1 | |
|
Ottawa Village Putnam County |
4,393 | 3 | 0 | |
|
Hamler Village Henry County |
580 | 3 | 1 | |
|
Monroe Elementary School Madison County |
287 | 2 | 1 | |
|
Lima City Allen County |
65,619 | 2 | 0 | |
|
Sidney City PWS Shelby County |
20,614 | 2 | 1 | |
|
Northwestern W and SD Toledo Svc Area Wood County |
19,332 | 2 | 1 | |
|
Monroe City PWS Butler County |
15,600 | 3 | 1 | |
|
Jefferson CO W and S District M Jefferson County |
13,983 | 4 | 2 | |
|
Bedford City PWS Cuyahoga County |
13,149 | 2 | 0 | |
|
Urbana City PWS Champaign County |
11,428 | 4 | 0 | |
|
Buckeye Water District Ohio River Columbiana County |
10,300 | 3 | 1 | |
|
Guernsey Co. Water Dept. Guernsey County |
8,891 | 2 | 1 | |
|
Aqua Ohio Lawrence County Lawrence County |
8,130 | 1 | 0 | |
|
Wauseon City PWS Fulton County |
7,568 | 2 | 1 | |
|
Stark County Water District Stark County |
6,690 | 1 | 0 | |
|
Leading Creek Conservancy District Meigs County |
6,663 | 3 | 1 | |
|
Brookville Municipality PWS Montgomery County |
5,923 | 2 | 0 | |
|
New Lexington Perry County |
5,161 | 3 | 1 | |
|
Oak Harbor Village Ottawa County |
4,400 | 2 | 1 | |
|
Wintersville Village PWS Jefferson County |
3,924 | 3 | 2 | |
|
Miami Co-Camp Troy PWS Miami County |
3,813 | 2 | 0 | |
|
Hicksville Village Defiance County |
3,600 | 5 | 3 | |
|
Delta Village Fulton County |
3,518 | 2 | 1 | |
|
Cadiz Village PWS Harrison County |
3,353 | 6 | 0 | |
|
Western Guernsey Regional Water District Guernsey County |
3,225 | 2 | 1 | |
|
Dayton Vamc Water Treatment Plant-Bld330 Montgomery County |
3,216 | 2 | 0 | |
|
Fairport Harbor Village PWS Lake County |
3,180 | 2 | 0 | |
|
Bridgeport Public Water System Belmont County |
2,830 | 4 | 3 | |
|
Clear Water Corporation Noble County |
2,670 | 3 | 2 | |
|
Jefferson CO W and S District a Jefferson County |
2,635 | 4 | 2 | |
|
Woodsfield Village PWS Monroe County |
2,598 | 3 | 1 | |
|
Crooksville Perry County |
2,534 | 4 | 1 | |
|
Lagrange Village PWS Lorain County |
2,400 | 3 | 1 | |
|
Gambier Village PWS Knox County |
2,300 | 1 | 0 | |
|
Piketon Village PWS Pike County |
2,181 | 4 | 2 | |
|
Manchester Village Adams County |
2,043 | 4 | 0 | |
|
Navarre Village PWS Stark County |
1,957 | 3 | 2 | |
|
Pomeroy Village PWS Meigs County |
1,800 | 6 | 4 | |
|
New Paris Village PWS Preble County |
1,681 | 4 | 2 | |
|
Lithopolis Village PWS Fairfield County |
1,573 | 4 | 2 | |
|
Jackson Center Village PWS Shelby County |
1,462 | 3 | 2 | |
|
Campbell Soup Supply CO Henry County |
1,300 | 5 | 0 | |
|
Holgate Village Henry County |
1,150 | 3 | 0 | |
|
Hillsdale School Pk-12 PWS Ashland County |
1,056 | 5 | 0 | |
|
Wakeman Village PWS Huron County |
1,047 | 2 | 0 | |
|
Yorkville Village PWS Jefferson County |
1,019 | 5 | 2 | |
|
Glandorf Village Putnam County |
1,001 | 2 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved TTHM (Total Trihalomethanes), including monitoring and reporting lapses. Rules violated and status in the table are for the whole system, not TTHM (Total Trihalomethanes) alone.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Ohio records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.