Cook County Water Quality: 676 Violations (IL)
168 water systems · 168 ZIP codes · Average ZIP-level Home Safety model score 68/100 (C) · 162 of 218 tracked ZIP records scored
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO
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Find the Right Filter →Water Quality Overview
Cook County has 168 community water systems across 168 directly mapped ZIP records. The systems report serving approximately 5,614,471 people. The available records contain 676 EPA violations, including 15 health-based violations.
Health-based violations account for 2% of all violations in Cook County. These violations indicate contaminant levels that may pose direct risks to human health.
Year-by-year violation counts, enforcement actions and violation counts by contaminant are not shown for this county: the source records them per ZIP code, so a water system serving several ZIP codes would be counted several times. The county totals above count each water system once.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 15 | 2.2% |
| Monitoring/Reporting | 661 | 97.8% |
| Total | 676 | 100% |
Health-based violations are MCL, MRDL (disinfectant) and treatment-technique violations. Monitoring violations indicate failures to test or report.
Cities with Most Violations
| Rank | City | Violations | Health-Based | ZIP Codes | Population |
|---|---|---|---|---|---|
| 1 | Chicago Heights | 144 | 0 | 1 | 52,395 |
| 2 | Chicago | 72 | 3 | 56 | 2,691,226 |
| 3 | Park Forest | 70 | 2 | 1 | 21,123 |
| 4 | Harvey | 68 | 2 | 1 | 23,066 |
| 5 | South Holland | 63 | 3 | 1 | 21,407 |
| 6 | Blue Island | 57 | 0 | 1 | 24,887 |
| 7 | Arlington Heights | 51 | 0 | 2 | 80,906 |
| 8 | Riverdale | 51 | 0 | 1 | 24,887 |
| 9 | Matteson | 51 | 1 | 1 | 20,606 |
| 10 | Mount Prospect | 48 | 0 | 1 | 55,989 |
Most Common Contaminants
| Contaminant | Category | ZIPs Affected | Health-Based |
|---|---|---|---|
| Consumer Confidence Rule | Reporting | 147 | No |
| Public Notice Rule | Reporting | 72 | No |
| Total organic carbon | Disinfection Byproducts | 62 | No |
| Lead and Copper Rule | Treatment Technique | 123 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 84 | No |
| Lead and Copper Rule Revisions | Treatment Technique | 124 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 73 | No |
| Interim Enhanced Surface Water Treatment Rule | Treatment Technique | 63 | Yes |
| Chlorine | Disinfectant | 38 | No |
| Combined Radium (-226 and -228) | Radionuclides | 16 | Yes |
Water Data and the Home Safety Score
This page reports EPA water-system facts without converting the broader Home Safety Score into a drinking-water grade. The county Home Safety grade (C) is a separate multi-source index that also requires PFAS screening, radon, and annual air-quality evidence. Check each ZIP report for the versioned score and its component coverage.
Water Systems in Cook County
Cook County is served by 168 community water systems, averaging 0.8 systems per ZIP code. Each system is independently regulated and tested by the EPA. Larger systems serving more people typically have more extensive monitoring requirements.
Water systems in Cook County source water from a mix of surface water (rivers, reservoirs) and groundwater (wells, aquifers). Source type affects which contaminants are most likely to be detected.
How to Check Your Water in Cook County
Enter your ZIP code on ZipCheckup for detailed water-system data including contaminant levels and violation history; the Home Safety Score is shown separately with its model version
Request your CCR — every water utility must provide an annual Consumer Confidence Report
Get a home test — certified kits ($20-$50) or professional lab tests ($150-$400) can detect contaminants not covered by routine testing
Consider filtration — NSF-certified filters can address specific contaminants found in your area
Check for lead — homes built before 1986 should test for lead regardless of utility compliance
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Source publication schedules vary. See the page source and verification fields for available timing evidence.
Water Quality by ZIP Code in Cook County
Water quality varies across Cook County's 168 ZIP codes. Each row counts the EPA violations of every water system mapped to that ZIP, so a system serving several ZIP codes appears in several rows and the rows do not add up to the county total. Check your specific ZIP for detailed contaminant data.
| ZIP Code | City | Violations | Health | |
|---|---|---|---|---|
| 60411 | Chicago Heights | 144 | 0 | View → |
| 60466 | Park Forest | 70 | 2 | View → |
| 60426 | Harvey | 68 | 2 | View → |
| 60473 | South Holland | 63 | 3 | View → |
| 60406 | Blue Island | 57 | 0 | View → |
| 60443 | Matteson | 51 | 1 | View → |
| 60827 | Riverdale | 51 | 0 | View → |
| 60056 | Mount Prospect | 48 | 0 | View → |
| 60005 | Arlington Heights | 47 | 0 | View → |
| 60418 | Crestwood | 47 | 0 | View → |
| 60471 | Richton Park | 47 | 2 | View → |
| 60008 | Rolling Meadows | 44 | 0 | View → |
| 60472 | Robbins | 40 | 0 | View → |
| 60409 | Calumet City | 39 | 3 | View → |
| 60007 | Elk Grove Village | 37 | 1 | View → |
| 60089 | Buffalo Grove | 37 | 0 | View → |
| 60004 | Arlington Heights | 36 | 0 | View → |
| 60070 | Prospect Heights | 33 | 0 | View → |
| 60068 | Park Ridge | 31 | 1 | View → |
| 60633 | Chicago | 31 | 1 | View → |
What are EPA health violations?
Health-based violations are EPA violations of a Maximum Contaminant Level (MCL), a Maximum Residual Disinfectant Level (MRDL) or a required treatment technique - the enforceable standards designed to protect human health. Cook County has 15 such violations. Not all violations cause illness; review each violation type and duration to understand possible health implications.
Water facts and the Home Safety Score
The score shown here is the broader Home Safety Score, not a water-quality grade. Model 4.0.0 combines EPA SDWIS identity plus accepted ECHO SDWA lifecycle-based water compliance, PFAS screening, radon zones, and annual air-quality evidence. Cook County has a score of 68/100 (Grade C) across 162 scored of 218 tracked ZIP records.
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Find the Right Filter →Frequently Asked Questions
Is the tap water safe in Cook County, Illinois?
Cook County has 168 community water systems with 676 recorded EPA violations, including 15 health-based. Water quality varies by ZIP code - check your specific location for detailed results.
How many water violations does Cook County have?
The 168 water systems with EPA records that serve ZIP codes in Cook County have 676 recorded EPA violations, each system counted once. 15 are health-based.
Which city in Cook County has the most water violations?
Chicago Heights has the most violations in Cook County with 144 recorded EPA violations for the 11 water systems serving its 1 ZIP code.
What contaminants are found in Cook County water?
Cook County water systems are monitored for over 90 EPA-regulated contaminants including lead, copper, nitrates, disinfection byproducts, and bacteria. Check your ZIP code for contaminant-specific data.
How can I test my water in Cook County?
Contact your local water utility for free or low-cost testing. You can also use a certified home test kit ($20-$50) or hire a certified lab ($150-$400).