Illinois
Cook County drinking water quality
423 active public water systems serve 5,279,874 people in Cook County. 203 are compliant, 220 had at least one EPA violation in the past three years, 43 are designated serious violators, and 5 carry a health flag.
Needs attention
37 more systems with a serious violator or health flag designation are in the lists below.
Community water systems
163 systems, largest first| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
Justice-Willow Springs Water Commission Justice |
18,450 | 0 | 0 | |
|
Matteson Matteson |
18,293 | 5 | 2 | |
|
Country Club Hills Country Club Hills |
16,500 | 2 | 1 | |
|
Bridgeview Bridgeview |
16,467 | 0 | 0 | |
|
Westchester Westchester |
16,241 | 2 | 0 | |
|
LA Grange La Grange |
16,200 | 1 | 1 | |
|
Palos Heights Palos Heights |
15,500 | 1 | 0 | |
|
Norridge Norridge |
15,251 | 0 | 0 | |
|
Midlothian Midlothian |
14,819 | 1 | 1 | |
|
Hickory Hills Hickory Hills |
14,505 | 0 | 0 | |
|
Forest Park Forest Park |
14,340 | 2 | 0 | |
|
Chicago Ridge Chicago Ridge |
14,130 | 0 | 0 | |
|
Hazel Crest Hazel Crest |
13,792 | 2 | 1 | |
|
Western Springs Western Springs |
13,629 | 3 | 1 | |
|
Lincolnwood Lincolnwood |
13,463 | 1 | 0 | |
|
LA Grange Park La Grange Park |
13,011 | 2 | 0 | |
|
Northlake North Lake |
12,840 | 2 | 0 | |
|
Richton Park Richton Park |
12,504 | 5 | 3 | |
|
Markham Markham |
12,500 | 4 | 1 | |
|
Winnetka Winnetka |
12,475 | 0 | 0 | |
|
River Forest River Forest |
11,717 | 2 | 1 | |
|
Schiller Park Schiller Park |
11,709 | 1 | 1 | |
|
IL American-Chicago Suburban |
11,187 | 0 | 0 | |
|
Summit Summit |
11,161 | 3 | 3 | |
|
Worth Worth |
10,970 | 1 | 0 | |
|
Crestwood Crestwood |
10,826 | 2 | 1 | |
|
Lyons Lyons |
10,304 | 1 | 1 | |
|
River Grove River Grove |
10,282 | 1 | 0 | |
|
Riverdale Riverdale |
10,266 | 1 | 1 | |
|
Leyden Twsp Water District |
10,000 | 0 | 0 | |
|
Sauk Village Sauk |
9,921 | 4 | 0 | |
|
Steger Steger |
9,700 | 2 | 1 | |
|
Lynwood Lynwood |
9,698 | 1 | 0 | |
|
Flossmoor Flossmoor |
9,371 | 1 | 1 | |
|
Riverside Riverside |
9,298 | 1 | 0 | |
|
Harwood Heights Harwood Heights |
9,065 | 0 | 0 | |
|
Glenwood Glenwood |
8,956 | 3 | 0 | |
|
Glencoe Forest Park |
8,849 | 0 | 0 | |
|
Calumet Park Calumet Park |
8,442 | 3 | 2 | |
|
Hillside Hillside |
8,200 | 0 | 0 | |
|
Broadview Broadview |
7,847 | 4 | 3 | |
|
North Riverside North Riverside |
7,071 | 0 | 0 | |
|
Stickney Stickney |
6,902 | 2 | 0 | |
|
LA Grange Highlands Sanitary District |
6,600 | 1 | 1 | |
|
Countryside Countryside |
6,420 | 1 | 0 | |
|
Northfield Northfield |
5,751 | 1 | 1 | |
|
IL American-Fernway Westhaven |
5,521 | 0 | 0 | |
|
Robbins Robbins |
5,415 | 6 | 3 | |
|
Posen Posen |
5,331 | 3 | 1 | |
|
Berkeley Berkeley |
5,214 | 0 | 0 |
Non-community systems (260: schools, campgrounds, workplaces, restaurants)
These systems serve places people visit rather than homes.
Inactive systems (2,682, no longer operating or reporting)
Kept for the record and excluded from the county totals above. Browse inactive systems.
About this data
Totals cover active systems. Systems serving more than one county are counted in each county. EPA counts the rules a system was in violation of, not the individual violations; one rule can carry several.
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.