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Counties → Illinois

Cook County, Illinois

Water Systems
427
Population Served
5,304,996
Total Violations
21,728
1,894 health-based
PFAS Detected
13
of 114 tested

Violation Analysis

70.5%
Systems with Violations
50.9
Avg Violations per System
8.7%
Health-Based Violations

Water Source Types

SW
49 systems (11%)
GW
1 system (0%)

PFAS Contamination

114
Systems Tested
13
PFAS Detected
11.4%
Detection Rate

PFAS (per- and polyfluoroalkyl substances) are persistent chemicals found in drinking water. The EPA has set enforceable limits for several PFAS compounds under UCMR5 monitoring.

Compliance Snapshot

Cook Illinois water systems by violation status, EPA SDWIS records.

No violations on record (0) One or more violations (50)

Violation history is cumulative, many flagged systems have already returned to compliance. Detail pages show per-system context.

Water Systems

System Name Population Violations PFAS
Chicago 2,746,388 212 Clean
Cicero 83,000 43 Clean
Schaumburg 75,750 22 Clean
Evanston 74,486 99 Clean
Arlington Heights 73,320 79 Clean
Palatine 70,875 28 Clean
Skokie 66,422 26 Clean
Des Plaines 60,675 17 Clean
Orland Park 58,862 20 Clean
Oak Lawn 58,362 39 Clean
Berwyn 57,250 70 Clean
Tinley Park 56,703 42 Clean
Oak Park 54,583 29 Clean
Hoffman Estates 50,179 42 Clean
Glenview 47,856 29 Clean
Buffalo Grove 43,212 13 Clean
Bartlett 41,500 300 Clean
Mount Prospect 41,000 49 Clean
Park Ridge 39,800 19 Clean
Wheeling 39,725 43 Clean
Streamwood 39,577 27 Clean
Hanover Park 37,470 102 Clean
Calumet City 37,000 64 Detected
Elk Grove Village 34,700 41 Clean
Northbrook 34,407 25 Clean
Aqua Illinois-North Maine Utilities 30,043 89 Clean
South Stickny SD 30,000 73 Clean
Niles 29,350 23 Clean
Lansing 29,076 33 Clean
Oak Forest 27,478 24 Detected
Wilmette 27,087 26 Clean
Chicago Heights 26,184 40 Clean
Morton Grove 25,297 23 Clean
Elmwood Park 25,000 39 Clean
Harvey 25,000 41 Clean
Melrose Park 24,206 132 Clean
Maywood 24,090 104 Clean
Rolling Meadows 23,329 36 Clean
South Holland 22,000 37 Detected
Park Forest 21,975 154 Clean
Blue Island 21,494 23 Clean
Dolton 20,510 83 Clean
Evergreen Park 19,943 10 Clean
Homewood 19,463 22 Detected
Bellwood 19,156 53 Clean
Alsip 19,063 22 Clean
Brookfield 18,776 48 Clean
Palos Hills 18,530 18 Clean
Franklin Park 18,467 41 Clean
Justice-Willow Springs Water Commission 18,457 26 Clean

Other Counties in Illinois

DuPage County
207 systems · 861,775 served · 15,779 violations
Lake County
540 systems · 719,035 served · 33,311 violations
Will County
330 systems · 622,572 served · 37,818 violations
Kane County
191 systems · 592,544 served · 12,844 violations
McHenry County
307 systems · 271,051 served · 11,554 violations
Madison County
68 systems · 268,778 served · 1,940 violations

Drinking Water Guides

Frequently Asked Questions

How many water violations are in Cook County? ▼
Cook County has 21,728 total drinking water violations across 427 water systems, of which 1,894 are health-based violations. 70.5% of systems have at least one violation.
How many people get water from Cook County systems? ▼
Water systems in Cook County serve approximately 5,304,996 people through 427 public water systems.
Has PFAS been detected in Cook County water? ▼
Of 114 water systems tested for PFAS in Cook County, 13 had PFAS detected (11.4% detection rate).
What types of water sources supply Cook County? ▼
Water systems in Cook County use SW (49 systems), GW (1 systems) as their primary water sources.
Are health-based violations serious? ▼
Health-based violations indicate that drinking water exceeded Maximum Contaminant Levels (MCLs) set by the EPA or failed treatment technique requirements. 8.7% of Cook County's violations are health-based. Not all violations indicate immediate health risk, but they require corrective action.
Data Sources & Methodology

Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). PFAS testing data from the UCMR5 monitoring program. SDWIS tracks all public water systems regulated under the Safe Drinking Water Act.

Violations are categorized as health-based (Maximum Contaminant Level exceedances, treatment technique failures) or monitoring/reporting violations. Not all violations indicate an immediate health risk.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.