Public water system · IL0431100
ActiveWillowbrook
At a glance
Willowbrook (PWSID IL0431100) is an active community water system in DuPage County, Illinois. It reports serving 9,000 people through 2,207 service connections. Its primary water source is purchased surface water, and EPA lists it as owned by a local government. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2025.
Dataset updated . Source: EPA SDWIS/ECHO public records.
Population served
9,000
Service connections
2,207
Primary source
SWP
Purchased surface water
System type
CWS
Community water system
System record
How does Willowbrook compare with other water systems in DuPage County?
By EPA's size categories, Willowbrook is a medium system (3,301 to 10,000 people). DuPage County has 125 active public water systems. Its population served is about 31% above the county average of 6,865 people per system, and accounts for 1% of the 858,100 people reported by systems filed under the county. Across Illinois, the 3,872 active systems average 3,204 people each. Nationally, the average active community water system reports serving 6,703 people, so Willowbrook is about 34% above that figure.
What does “community water system” mean?
A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. Illinois has 1,773 active community water systems, 46% of the state's 3,872 active systems. Purchased surface water means the system buys surface water from another public water system rather than drawing its own. 619 Illinois systems (16%) list purchased surface water as their primary source.
Who owns and regulates Willowbrook?
EPA lists Willowbrook as owned by a local government. The IL state drinking water program is its primacy agency, the regulator with primary enforcement responsibility for the system under the Safe Drinking Water Act. 32 of the 125 active systems in DuPage County (26%) are also owned by a local government.
Does Willowbrook have drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2025. The violations listed here began between June 1977 and July 2025. By type: 5 public notice, recordkeeping or other, 5 monitoring and reporting, 1 reporting and 1 contaminant level above the legal limit. The contaminant or rule involved most often is Consumer Confidence Rule (5 of them). EPA lists 7 as resolved, 3 as archived and 2 as unaddressed. Resolved means at least one resolving action is on record: the system returned to compliance, the rule no longer applies, or no further action was needed. Archived means the violation was not marked resolved but is more than five years past the end of the noncompliance period, so it no longer counts toward current compliance status. Unaddressed means the violation is not resolved or archived and is not yet covered by formal enforcement.
| Began | Violation | Contaminant or rule | Health-based | Status |
|---|---|---|---|---|
| 2025-07-02 | ReportingNotification, Known or Potential LSL · code 4H | Lead and Copper Rule Revisionscode 5200 | No | Unaddressed |
| 2025-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Unaddressed |
| 2024-10-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Haloacetic acids (HAA5)code 2456 | No | Resolved |
| 2024-10-01 | Monitoring and reportingMonitoring and Reporting (DBP) · code 27 | Total trihalomethanes (TTHM)code 2950 | No | Resolved |
| 2023-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2022-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Inadequate Reporting · code 72 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2021-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 2020-12-30 | Monitoring and reportingLead Consumer Notice · code 66 | Lead and Copper Rulecode 5000 | No | Resolved |
| 2013-07-01 | Public notice, recordkeeping or otherConsumer Confidence Report Complete Failure to Report · code 71 | Consumer Confidence Rulecode 7000 | No | Resolved |
| 1993-07-01 | Monitoring and reportingMonitoring, Routine Minor (TCR) · code 24 | Total coliform bacteria (TCR)code 3100 | No | Archived |
| 1985-12-06 | Contaminant level above the legal limitMaximum Contaminant Level Violation, Average · code 02 | Combined Radium (-226 and -228)code 4010 | Yes | Archived |
| 1977-06-30 | Monitoring and reportingMonitoring, Regular · code 03 | Gross alpha (excluding radon and uranium)code 4000 | No | Archived |
The 12 most recent violations in EPA's records, newest first.Labels and codes come from EPA's SDWIS reference tables. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found. "Health-based" marks violations of a legal limit or required treatment.
Willowbrook: frequently asked questions
Who runs Willowbrook?
Willowbrook (PWSID IL0431100) is a community water system owned by a local government. It is regulated by the IL state drinking water program.
How many people does Willowbrook serve?
Willowbrook reports serving 9,000 people through 2,207 service connections in DuPage County, Illinois.
Where does Willowbrook get its water?
EPA SDWIS lists this system's primary water source as purchased surface water. Purchased surface water means the system buys surface water from another public water system rather than drawing its own.
Does Willowbrook have any drinking water violations?
Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2025. A monitoring or reporting violation means a required test or report was missed or late; it does not by itself mean a contaminant was found.
Is Willowbrook's water safe to drink?
AquaCensus shows EPA compliance records, not current water test results, so it cannot say whether the water is safe at a given moment. Of the 12 most recent violations in EPA's records, one is health-based, and the most recent began in July 2025. For current results, consult the system's annual water quality report, EPA ECHO, or the IL state drinking water program.
Where can I find Willowbrook's water quality report?
As a community water system, Willowbrook must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1 each year, covering the previous calendar year. The system can provide a copy on request.
Other water systems in DuPage County
| Water system | County | Population served | Type | Source |
|---|---|---|---|---|
| Naperville | DuPage | 156,406 | Community | Purchased surface water |
| Wheaton | DuPage | 53,970 | Community | Purchased surface water |
| Downers Grove | DuPage | 49,425 | Community | Purchased surface water |
| Elmhurst | DuPage | 45,000 | Community | Purchased surface water |
| Lombard | DuPage | 44,476 | Community | Purchased surface water |
| Carol Stream | DuPage | 39,854 | Community | Purchased surface water |
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About this data
Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.
Cite as: AquaCensus, “Willowbrook, PWSID IL0431100, Illinois”, https://aquacensus.com/water-systems/illinois/willowbrook-il0431100 (data as of October 1, 2026).