TTHM (Total Trihalomethanes) violations in Illinois
355 active public water systems in Illinois had a TTHM (Total Trihalomethanes) violation in the past three years, 50 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 |
|---|---|---|---|---|
|
Springfield Springfield · Sangamon County |
117,444 | 2 | 0 | |
|
Waukegan Waukegan · Lake County |
87,149 | 3 | 1 | |
|
Aqua Illinois-Kankakee Kankakee · Kankakee County |
80,000 | 5 | 0 | |
|
Skokie Skokie · Cook County |
66,422 | 4 | 1 | |
|
Wheaton Wheaton · DuPage County |
53,970 | 1 | 0 | |
|
O Fallon O Fallon · St. Clair County |
46,603 | 1 | 0 | |
|
Moline Moline · Rock Island County |
44,500 | 2 | 0 | |
|
Buffalo Grove Buffalo Grove · Cook County |
43,212 | 2 | 0 | |
|
Addison Addison · DuPage County |
38,017 | 1 | 0 | |
|
Hanover Park Hanover Park · Cook County |
37,470 | 2 | 1 | |
|
Vernon Hills Lake CO PW Vernon Hills · Lake County |
33,207 | 1 | 0 | |
|
Glendale Heights Glendale Heights · DuPage County |
33,176 | 1 | 0 | |
|
Mundelein Mundelein · Lake County |
31,500 | 1 | 0 | |
|
EJ Water Cooperative Jasper County |
29,720 | 5 | 1 | |
|
Lansing Lansing · Cook County |
29,076 | 4 | 3 | |
|
Lake in the Hills Lake In The Hills · McHenry County |
28,661 | 1 | 0 | |
|
Wilmette Wilmette · Cook County |
27,650 | 2 | 1 | |
|
Chicago Heights Chicago Heights · Cook County |
26,184 | 2 | 0 | |
|
Woodstock Woodstock · McHenry County |
25,630 | 3 | 0 | |
|
Maywood Maywood · Cook County |
24,090 | 4 | 2 | |
|
Roselle Roselle · DuPage County |
22,897 | 2 | 0 | |
|
Dolton Dolton · Cook County |
20,510 | 5 | 2 | |
|
Crest Hill Crest Hill · Will County |
20,223 | 10 | 2 | |
|
Mokena Mokena · Will County |
19,887 | 1 | 0 | |
|
Deerfield Deerfield · Lake County |
19,196 | 3 | 1 | |
|
Bellwood Bellwood · Cook County |
19,156 | 4 | 2 | |
|
Shorewood Shorewood · Will County |
18,645 | 3 | 0 | |
|
Sycamore Sycamore · DeKalb County |
18,500 | 2 | 0 | |
|
Matteson Matteson · Cook County |
18,293 | 5 | 2 | |
|
Ottawa Ottawa · LaSalle County |
18,097 | 3 | 0 | |
|
Hinsdale Hinsdale · DuPage County |
17,900 | 1 | 0 | |
|
Macomb Macomb · McDonough County |
15,051 | 3 | 1 | |
|
Hazel Crest Hazel Crest · Cook County |
13,792 | 2 | 1 | |
|
Northlake North Lake · Cook County |
12,840 | 2 | 0 | |
|
Jersey Rwc Jersey County |
12,750 | 1 | 0 | |
|
Herrin Herrin · Williamson County |
12,747 | 6 | 0 | |
|
Glen Carbon Glen Carbon · Madison County |
12,618 | 2 | 1 | |
|
Richton Park Richton Park · Cook County |
12,504 | 5 | 3 | |
|
Markham Markham · Cook County |
12,500 | 4 | 1 | |
|
Captain James a Lovell Fhcc Lake County |
12,100 | 6 | 2 | |
|
Robinson-Palestine Water Commission Crawford County |
11,331 | 3 | 0 | |
|
Burr Ridge Burr Ridge · DuPage County |
11,192 | 1 | 0 | |
|
Crestwood Crestwood · Cook County |
10,826 | 2 | 1 | |
|
Highland Highland · Madison County |
10,674 | 3 | 0 | |
|
Pingree Grove Hampshire · Kane County |
10,365 | 4 | 1 | |
|
Murphysboro Murphysboro · Jackson County |
10,241 | 3 | 1 | |
|
Waterloo Waterloo · Monroe County |
10,190 | 7 | 0 | |
|
Advocate Christ Medical Center Cook County |
10,000 | 5 | 1 | |
|
Sauk Village Sauk · Cook County |
9,921 | 4 | 0 | |
|
Riverside Riverside · Cook County |
9,298 | 1 | 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 Illinois 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.