Naperville Water Quality Summary
Naperville supplies drinking water to about 156,406 people in Naperville, Illinois, and draws from surface water (rivers, lakes, or reservoirs), which requires fuller treatment for runoff, sediment, and microbial risk. On the IsWaterSafe scale it earns a good Water Safety Score of 88 out of 100 (Grade B), a composite of its EPA SDWIS violation and contaminant record.
EPA SDWIS shows no health-based or monitoring violations on record for Naperville, though 4 enforcement actions are logged in its history.
Across the single substance sampled, none exceeded its EPA limit. Haloacetic Acids (HAA5) sits highest relative to its ceiling, detected at 30 ppb against an MCL of 60 ppb (sampled April 2023) — within the legal limit.
The most pressing open issue is a treatment technique violation involving Haloacetic Acids (HAA5), beginning April 2023 and still open in EPA records.
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Detected Contaminants
| Contaminant | Detected Level | MCL (Limit) | Status | Sample Date |
|---|---|---|---|---|
| Haloacetic Acids (HAA5) | 30 ppb | 60 ppb | Within Limit | Apr 1, 2023 |
Violation History
Frequently Asked Questions
Naperville has a Water Safety Score of B (88/100). The system serves 156,406 people and has 0 health violations on record. Check the contaminant table above for specific detected substances.
Naperville has 0 contaminant exceedances above EPA health guidelines. See the full contaminant detection table above for all tested substances and their levels relative to legal limits and health guidelines.
The Water Safety Score (0-100, grades A through F) is based on contaminant levels relative to legal limits, health guideline exceedances, violation history, and enforcement actions. Higher scores indicate fewer concerns.
If your water system has violations, request the Consumer Confidence Report from your utility, consider getting an independent water test from a certified lab, and look into certified water filters for specific contaminants of concern. For lead, run cold water for 30 seconds before drinking.
Water quality data sourced from EPA's Safe Drinking Water Information System (SDWIS). Safety scores are calculated based on contaminant levels, violations, and enforcement history. This is not a substitute for your utility's official Consumer Confidence Report.
Source: EPA Ground Water and Drinking Water, 2026.