Community Water System · PWS IL0430700
Oak Brook
Oak Brook, Illinois 60523 - drinking water served from surface water sources to 9,400 people, tracked in EPA SDWIS and UCMR5.
- 9,400
- People served
- 54
- EPA violations
- 35
- Health-based
- No PFAS
- UCMR5 result
The verdict
EPA records 54 drinking-water violations at Oak Brook, 65% of them health-based - below the Illinois per-system average.
- 54
- Total EPA violations on record
- 65%
- Health-based (MCL / treatment failure)
- 9,400
- People served by this system
- 0
- PFAS compounds detected (UCMR5)
Water Quality Snapshot: Oak Brook
Oak Brook is a local-owned community water system that delivers drinking water to 9,400 residents in Oak Brook, Illinois (DuPage County) through 3,295 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 54 total violations for this system , of which 35 (65%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 13 monitoring and reporting violations are on file. The most recent violation on record dates to 2024.
The most frequently cited contaminant at this system is Combined Radium (-226 and -228), recorded in 22 violations (MCL, health-based). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.
Across Illinois, EPA tracks 5,117 public water systems serving 12,576,876 people, with 355,322 cumulative violations and 52,932 health-based violations on record. About 81% of systems in the state carry at least one violation, and state-wide the average per system is 69.4 violations. Statewide, 199 of 487 UCMR5-tested systems have reported PFAS detections (40.9%).
Oak Brook's 54 violations sit below the Illinois average.
All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.
System Details
- System Type
- Community
- Owner Type
- Local
- Connections
- 3,295
- County
- DuPage
- School/Daycare
- No
- MCL Violations
- 35
- Monitoring Violations
- 13
- Treatment Tech Violations
- 0
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Combined Radium (-226 and -228) | MCL | 22 | 1989 |
| Gross Alpha, Excl. Radon and U | MCL | 13 | 1985 |
| Chlorine | MR | 4 | 2005 |
| Lead and Copper Rule | MR | 4 | 2023 |
| Total Haloacetic Acids (HAA5) | MR | 4 | 2024 |
| Consumer Confidence Rule | Other | 2 | 2024 |
| Gross Alpha, Excl. Radon and U | MR | 1 | 1977 |
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 116 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| 4:2 FTS | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 9Cl-PF3ONS | 5/9/2024 | <2.00 ppt | 2.00 ppt | Not Detected |
| ADONA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 5/9/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFBA | 5/9/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFMPA | 5/9/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFPeA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMBA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFEESA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 5/9/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFPeS | 5/9/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHxS | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpS | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NFDHA | 5/9/2024 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFUnA | 5/9/2024 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFHxA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOA | 5/9/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFNA | 5/9/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpA | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 5/9/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFTA | 5/9/2024 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFTrDA | 5/9/2024 | <7.00 ppt | 7.00 ppt | Not Detected |
| NEtFOSAA | 5/9/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| NMeFOSAA | 5/9/2024 | <6.00 ppt | 6.00 ppt | Not Detected |
| 8:2 FTS | 5/9/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFOS | 5/9/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| 6:2 FTS | 5/9/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFEESA | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOA | 2/8/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 2/8/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFNA | 2/8/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHxS | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFBS | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDA | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NFDHA | 2/8/2024 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFMBA | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFPeA | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpS | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NEtFOSAA | 2/8/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFTrDA | 2/8/2024 | <7.00 ppt | 7.00 ppt | Not Detected |
| PFTA | 2/8/2024 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFPeS | 2/8/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| 6:2 FTS | 2/8/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFDoA | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NMeFOSAA | 2/8/2024 | <6.00 ppt | 6.00 ppt | Not Detected |
| 4:2 FTS | 2/8/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMPA | 2/8/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
Verify This Water System
The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Oak Brook.
EPA SDWIS, Federal Reports
EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:
View PWS ID IL0430700 on SDWISSource: EPA SDWIS Federal Reports Search
Illinois Drinking Water Authority
Illinois EPA, Bureau of Water is the primacy agency that licenses and inspects Oak Brook under EPA-delegated authority.
Open IL regulator portalSource: Illinois EPA, Bureau of Water
Violation Timeline
Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.
| Year (latest) | Contaminant | Category | Count | EPA Record |
|---|---|---|---|---|
| 2024 | Total Haloacetic Acids (HAA5) | MR | 4 | SDWIS / IL0430700 / 2456 |
| 2024 | Consumer Confidence Rule | Other | 2 | SDWIS / IL0430700 / 7000 |
| 2023 | Lead and Copper Rule | MR | 4 | SDWIS / IL0430700 / 5000 |
| 2005 | Chlorine | MR | 4 | SDWIS / IL0430700 / 0999 |
| 1989 | Combined Radium (-226 and -228) | MCL | 22 | SDWIS / IL0430700 / 4010 |
| 1985 | Gross Alpha, Excl. Radon and U | MCL | 13 | SDWIS / IL0430700 / 4000 |
| 1977 | Gross Alpha, Excl. Radon and U | MR | 1 | SDWIS / IL0430700 / 4000 |
How Oak Brook Compares
Cross-reference this system's record against state averages and the federal MCL framework for context.
| Metric | Oak Brook | Illinois avg | Federal benchmark |
|---|---|---|---|
| Total violations | 54 | 69.4 | SDWA compliance, any non-zero count is a recorded breach |
| Health-based violations | 35 | 10.3 | Indicates a contaminant exceeded a federal MCL |
| PFAS detection | None | 40.9% | EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt |
| Population served | 9,400 | 2,458 | Sizing context for compliance burden |
Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 5,117 regulated public water systems in Illinois.
Federal MCL reference, Safe Drinking Water Act thresholds ▼
| Contaminant | Federal MCL / Action Level | Note |
|---|---|---|
| Lead | 0 mg/L (Action Level: 0.015 mg/L) | Lead and Copper Rule treatment technique |
| Arsenic | 0.010 mg/L (10 ppb) | Health-based MCL since 2006 |
| Total Coliform | Treatment technique (RTCR) | Indicator organism, monitoring trigger |
| PFOA / PFOS (PFAS) | 4.0 ppt each (final 2024 rule) | Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026) |
| Nitrate (as N) | 10 mg/L | Acute health risk for infants |
Frequently Asked Questions
Is Oak Brook water safe to drink? ▼
How many people does Oak Brook serve? ▼
What type of violations does Oak Brook have? ▼
Has PFAS been detected in Oak Brook water? ▼
What water source does Oak Brook use? ▼
Where does this data come from? ▼
Read our methodology - how this data is sourced, computed, and verified.
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.