Oak Brook
EPA ID: IL0430700 · 9,400 people served · 6 ZIP codes
Within the EPA compliance database, Oak Brook shows 3 violations still pending resolution — a status that applies across the full service territory of approximately 9,400 people and reflects findings that have not yet cleared the federal enforcement process or received formal closure.
Data: EPA SDWIS Last verified: 2026-04-02
Compliance Trajectory
Worsening · Risk tier: High · 95% chance of violation in next 12 months
Violations went from 2 (2024) to 1 (2025). The pattern suggests growing compliance challenges.
Service Area Map
Coverage area for Oak Brook Source: EPA SDWIS service area boundaries.
Service area boundary — Grade C
Service Area Demographics
The Oak Brook serves a community with a median household income of $117,888 and an estimated 159,564 residents across its service area. Approximately 74% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
🌊 Where Does Your Water Come From?
Oak Brook's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
About 1% of homes in DuPage County, Illinois rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Wastewater Proximity Note: This service area ranks in the 70th percentile nationally for proximity to wastewater discharge points. Surface water sources near wastewater outfalls may face additional treatment challenges.
Superfund Proximity Note: This service area ranks in the 70th percentile nationally for proximity to Superfund (NPL) sites.
Infrastructure Risk
Detected Contaminants
How Oak Brook compares to EPA limits
What This Means For You
Total Trihalomethanes (TTHM) at 1 mg/L exceeds the EPA maximum of 0.08 mg/L. Bladder & rectal cancer risk; reproductive concerns. Consider granular activated carbon (GAC) filtration.
Surface Water Treatment Rule at 3 mg/L exceeds the EPA maximum of mg/L.
Consumer Confidence Report Rule at 3 mg/L exceeds the EPA maximum of mg/L.
Revised Total Coliform Rule at 3 presence exceeds the EPA maximum of presence.
Contaminant 4109 at 2 mg/L exceeds the EPA maximum of mg/L.
PFAS Detected in Service Area
PFAS ("forever chemicals") have been detected in water serving this system's area. 1 detection recorded.
Total Trihalomethanes (TTHM) was detected in this water system. granular activated carbon (GAC) filtration can reduce exposure.
Find a certified water filter →Comparable Water Systems
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Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
Oak Brook (EPA ID: IL0430700) is a community water system in Illinois that serves approximately 9,400 people from surface water sources.
This system provides water to 6 ZIP codes across 6 communities.
Average Home Safety Score: C (60/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| July 1, 2025 | Stage 1 DBP Rule | Monitoring | Unresolved |
| July 1, 2025 | Surface Water Treatment Rule | Monitoring | Unresolved |
| July 1, 2025 | Gross Beta | Monitoring | Unresolved |
| July 1, 2024 | Total Trihalomethanes (TTHM) | Monitoring | Resolved |
| July 1, 2024 | Surface Water Treatment Rule | Monitoring | Resolved |
| March 29, 2024 | Lead and Copper Rule | Monitoring | Resolved |
| February 15, 2024 | Lead and Copper Rule | Monitoring | Resolved |
| October 1, 2023 | Stage 1 DBP Rule | Monitoring | Resolved |
| September 1, 2023 | Consumer Confidence Report Rule | Monitoring | Resolved |
| July 1, 2023 | Revised Total Coliform Rule | Monitoring | Resolved |
| February 1, 2023 | Consumer Confidence Report Rule | Monitoring | Resolved |
| January 1, 2023 | Revised Total Coliform Rule | Monitoring | Resolved |
| January 1, 2023 | Contaminant 4109 | Monitoring | Resolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Surface Water Treatment Rule | Treatment Failure | 3 | No |
| Consumer Confidence Report Rule | Reporting Failure | 3 | No |
| Revised Total Coliform Rule | Microbiological | 3 | No |
| Contaminant 4109 | Other Violation | 2 | No |
| Stage 1 DBP Rule | Treatment Failure | 2 | No |
| Lead and Copper Rule | Treatment Failure | 2 | No |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 1 | No |
| Gross Beta | Radionuclides | 1 | No |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
| ZIP Code | Lead Level | Exceeds Limit | Sample Date |
|---|---|---|---|
| 60523 | 0.00083 mg/L | No | N/A |
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 2 (Moderate Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
ZIP Codes Served
Coverage: Service area ZIP codes sourced from EPA Community Water System Service Area Boundaries v3 (March 2026 release). These ZIPs reflect the actual deployment footprint recorded by IL or modeled from parcel and building-footprint data.
- 60126 — Elmhurst
- 60181 — Villa Park
- 60515 — Downers Grove
- 60521 — Hinsdale
- 60523 — Oak Brook
- 60559 — Westmont
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View the full compliance record for Oak Brook (IL0430700) on EPA.gov.
Frequently Asked Questions
Is Oak Brook water safe to drink?
Oak Brook has only monitoring/reporting violations, which are procedural in nature. The system meets federal health-based standards.
How many people does Oak Brook serve?
Oak Brook serves approximately 9,400 people across 6 ZIP codes in Illinois.
Where does Oak Brook get its water?
The primary water source is surface water.
Water Source & Treatment
Where this water originates and how it's treated before reaching your tap.
Source: OAK BROOK Consumer Confidence Report.
ZipCheckup is not affiliated with this water utility. Treatment and source data are sourced from the utility's published CCR filings.
The source water assessment for our supply has been completed by the Illinois EPA. To view a summary version of the completed Source Water Assessments, including: Importance of Source Water; Susceptibility to Contamination Determination; and documentation/recommendation of Source Water Protection Efforts, you may access the Illinois EPA website at http://www.epa.state.il.us/cgi-bin/wp/swap-fact-sheets.pl.
Treatment regime
How this utility classifies its treatment process and what each reported treatment chemical does.
Treatment chemicals and what each one does
Chemical names are reported verbatim by the utility. Purpose categories are ZipCheckup annotations based on standard drinking-water treatment practice.
Watershed exposure sources reported
Land-use and natural conditions identified in the utility's source-water assessment as potential contamination sources upstream of treatment.
Treatment classification and chemical list sourced from OAK BROOK Consumer Confidence Report.
Treatment intensity is a ZipCheckup-derived classification based on the chemicals and processes the utility reports. Chemicals and contamination sources are taken verbatim from the utility's CCR filing. Routine federal monitoring and contaminant testing shown elsewhere on this page determine whether the water meets safety standards, not the treatment classification.
Federal UCMR5 PFAS Monitoring: Tested Clean
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). No PFAS compounds were detected.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Our Community Water Supply has/has not developed a service line material inventory. To obtain a copy of the system's service line inventory: ___________________________________________________________________
Lead Service Line Replacement Tracker
This water utility's lead service line (LSL) replacement program is tracked from public Consumer Confidence Report filings. Email signup notifies subscribers when the utility files an updated replacement plan or progress milestone.
OAK BROOK
ZipCheckup is not affiliated with this water utility. LSL replacement-program data is sourced from public CCR filings published by the utility. Subscription notifications are based on automated parsing of subsequent CCR releases.
Learn more about Lead and Copper Rule replacement requirements →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
Notable events and violations
This section summarizes events the utility chose to disclose in its most recent Consumer Confidence Report, plus any federal compliance violations the utility recorded against itself. Both lists are utility-authored — ZipCheckup does not audit, judge, or reorder them.
Federal compliance violations on record
These entries are taken verbatim from the utility's CCR violations section. EPA defines four broad violation categories: Maximum Contaminant Level (MCL), Treatment Technique (TT), Monitoring & Reporting (M&R), and Public Notification (PN).
-
public notice2024-07-01/2024
We failed to provide to you, our drinking water customers, an annual report that adequately informed you about the quality of our drinking water and the risks from exposure to contaminants detected in our drinking water.
-
monitoring · Haloacetic Acids (HAA5)2024-07-01/2024-09-30
We failed to test our drinking water for the contaminant and period indicated. Because of this failure, we cannot be sure of the quality of our drinking water during the period indicated.
-
monitoring2023-10-01/2024-02-27
We failed to test our drinking water for the contaminant and period indicated. Because of this failure, we cannot be sure of the quality of our drinking water during the period indicated.
Violations record from OAK BROOK Consumer Confidence Report.
ZipCheckup note: items above reflect what the utility published in its most recent CCR. Federal violation records are also tracked separately by the EPA Safe Drinking Water Information System (SDWIS) — the SDWIS record is the authoritative federal source for any specific regulatory action.
Frequently Asked Questions
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
Oak Brook (EPA ID: IL0430700) — request the latest Consumer Confidence Report or ask about specific contaminants.