TTHM (Total Trihalomethanes) violations in Pennsylvania
535 active public water systems in Pennsylvania had a TTHM (Total Trihalomethanes) violation in the past three years, 39 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 |
|---|---|---|---|---|
|
Pittsburgh Intl Airport Allegheny County |
26,915 | 5 | 0 | |
|
Highland S & W Auth Beaverdam Cambria County |
22,617 | 8 | 0 | |
|
Ambridge Water Auth Beaver County |
19,500 | 6 | 0 | |
|
Bradford City Water Authority McKean County |
18,500 | 6 | 1 | |
|
Phoenixville Water Dept Chester County |
16,599 | 8 | 0 | |
|
Highridge Water Auth Westmoreland County |
16,000 | 5 | 0 | |
|
Red Lion Municipal Authority York County |
15,882 | 4 | 0 | |
|
MT Joy Boro Auth Lancaster County |
15,261 | 1 | 0 | |
|
South Middleton Twp Water Auth Cumberland County |
11,695 | 6 | 0 | |
|
Findlay Twp Municipal Auth Allegheny County |
11,460 | 6 | 0 | |
|
Municipal Authority Sunbury Northumberland County |
11,043 | 6 | 1 | |
|
Tri Cnty JT Muni Auth Washington County |
10,100 | 7 | 3 | |
|
Downingtown Water Authority Chester County |
9,900 | 3 | 0 | |
|
Windber Area Auth Somerset County |
9,463 | 6 | 0 | |
|
Hollidaysburg Muni Auth Blair County |
8,523 | 2 | 0 | |
|
Hemlock Farms (main) Pike County |
8,321 | 8 | 0 | |
|
PA American Audubon Montgomery County |
8,200 | 8 | 0 | |
|
Upmc Presbyterian Allegheny County |
8,200 | 2 | 0 | |
|
Conemaugh Twp Muni Auth Somerset County |
7,800 | 11 | 0 | |
|
Municipal Authority of Corry Erie County |
7,800 | 3 | 0 | |
|
Edgeworth Boro Muni Auth Allegheny County |
7,781 | 2 | 0 | |
|
VA Pittsburgh UD Allegheny County |
6,701 | 1 | 0 | |
|
Kline Township Mun Authority Schuylkill County |
6,700 | 2 | 0 | |
|
Jersey Shore Area Jnt Wat Auth Lycoming County |
6,600 | 7 | 1 | |
|
Derry Boro Muni Auth Westmoreland County |
6,500 | 3 | 0 | |
|
Outlet Shops at Gettysburg Adams County |
6,500 | 3 | 0 | |
|
Kennett Square Mun Water Works Chester County |
6,328 | 9 | 1 | |
|
Titusville Municipal Water Crawford County |
6,146 | 1 | 0 | |
|
Coraopolis Water & Sewer Auth Allegheny County |
5,804 | 2 | 0 | |
|
MT Union Municipal Auth Huntingdon County |
5,801 | 5 | 1 | |
|
Duquesne Water Dept Allegheny County |
5,565 | 4 | 2 | |
|
Aqua PA Water CO Honesdale Wayne County |
5,500 | 1 | 0 | |
|
Birdsboro Muni Water Auth Berks County |
5,353 | 5 | 0 | |
|
Oxford Borough Chester County |
5,280 | 2 | 0 | |
|
Aqua PA Flying Hills WA Sys Berks County |
5,100 | 2 | 0 | |
|
Towanda Municipal Authority Bradford County |
5,000 | 4 | 0 | |
|
Danville Municipal Water Auth Montour County |
4,992 | 6 | 0 | |
|
Montoursville Water Company Lycoming County |
4,983 | 4 | 0 | |
|
Upmc Shadyside Hillman Campus Allegheny County |
4,750 | 1 | 0 | |
|
Ridgway Borough Water System Elk County |
4,700 | 1 | 0 | |
|
Fairview Twp Water District 1 Erie County |
4,500 | 2 | 0 | |
|
Northern Cambria Muni Water Cambria County |
4,500 | 5 | 0 | |
|
Pike Twp Municipal Authority Clearfield County |
4,500 | 5 | 0 | |
|
Milford Twp Water Authority Bucks County |
4,497 | 1 | 0 | |
|
New Freedom Boro Water Auth York County |
4,464 | 4 | 0 | |
|
Mifflintown Muni Auth Juniata County |
4,450 | 2 | 0 | |
|
Jackson Twp Water Auth Cambria County |
4,236 | 5 | 0 | |
|
Fleetwood Boro Water System Berks County |
4,218 | 3 | 0 | |
|
PA American Dilliner System Greene County |
4,200 | 7 | 0 | |
|
Mansfield Borough Mun Auth Tioga County |
4,100 | 9 | 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 Pennsylvania 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.