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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Water quality data for 7 cities serving 427,148 residents
DuPage County in Illinois has an average water quality score of 95/100 (Grade A) based on analysis of 7 municipal water systems. The county's water systems serve approximately 427,148 residents.
Overall, DuPage County demonstrates good water quality standards. 4 of 7 cities exceed the county average, with Downers Grove leading with a score of 100/100.
7 cities ranked by water quality score
| Rank | City | Score | Grade | Population |
|---|---|---|---|---|
| 1 | Downers Grove | 100 | A | 49,425 |
| 2 | Wheaton Biggest deduction: 1 monitoring/reporting violation in the last 5 years (−1 pts) | 99 | A | 53,970 |
| 3 | Addison Biggest deduction: 2 monitoring/reporting violations in the last 5 years (−2 pts) | 98 | A | 38,017 |
| 4 | Elmhurst Biggest deduction: Lead 90th-percentile tap result 7.21 ppb for 2025-07-01–2025-12-31, below the 15 ppb action level (−3 pts) | 95 | A | 45,000 |
| 5 | Carol Stream Biggest deduction: 4 monitoring/reporting violations in the last 5 years (−4 pts) | 94 | A | 39,854 |
| 6 | Lombard Biggest deduction: Lead 90th-percentile tap result 11.2 ppb for 2026-01-01–2026-06-30, below the 15 ppb action level (−10 pts) | 89 | B | 44,476 |
| 7 | Naperville Biggest deduction: 16 monitoring/reporting violations in the last 5 years (−10 pts) | 87 | B | 156,406 |
Real EPA readings across county water systems (lead: latest 90th percentile; PFAS: UCMR5 2023–2026; others: 2012–2019 averages)
| Contaminant | Avg Level | Max Level | EPA Limit | % of Limit | Cities |
|---|---|---|---|---|---|
| TTHM (2012–2019 avg) | 34.071 ug/L | 39.125 ug/L | 80 ug/L | 42.6% | 7 |
| Lead (90th percentile) | 5.26 ppb | 11.2 ppb | 15 ppb | 35.1% | 7 |
| HAA5 (2012–2019 avg) | 14.61 ug/L | 16.742 ug/L | 60 ug/L | 24.4% | 7 |
| PFAS (PFOA/PFOS max, UCMR5) | 0 ppt | 0 ppt | 4 ppt | 0% | 7 |
Recent violations across county water systems
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
6/30/2024
Monitoring & reporting — Monitoring and Reporting (DBP) - Total Haloacetic Acids (HAA5)
3/31/2023
Showing 10 of 20 recent violations
Water quality in DuPage County, Illinois reflects the region's unique combination of water sources, treatment infrastructure, and environmental factors. Our comprehensive analysis examines 7 municipal water systems serving a combined population of over 427,148 residents.
The county shows strong water quality performance, with scores ranging from 87/100 in Naperville to 100/100 in Downers Grove. This 13-point spread indicates relatively consistent water quality standards across municipal systems.
The most prevalent contaminants detected across DuPage County water systems include TTHM (2012–2019 avg), Lead (90th percentile), HAA5 (2012–2019 avg). Every county-wide average sits below 50% of its EPA Maximum Contaminant Level (MCL).
DuPage County's water quality is generally good. Residents can feel confident in their tap water quality, though those with specific health concerns or sensitivity to certain contaminants may still benefit from filtration. Regular review of your city's annual Consumer Confidence Report is recommended.
DuPage County has an average water quality score of 95/100 (Grade A) based on analysis of 7 municipal water systems serving 427,148 residents.
Downers Grove has the highest water quality score in DuPage County at 100/100. View the detailed report for Downers Grove.
Most cities in DuPage County have water that meets EPA standards. However, a water filter can provide additional protection and improve taste. The need depends on your specific city and any personal health considerations.
Click on any city in the rankings table above to view its detailed water quality report, including contaminant levels, EPA compliance history, and filter recommendations.