01The verdict: is Oak Brook Terr water safe?
Oak Brook Terr's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (80.1/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 2 water systems serve approximately 1,440 residents using surface water (rivers, lakes, or reservoirs).
Copper is over its legal limit
Measured at 1.57 mg/L against the EPA Action Level of 1.3 mg/L. The ledger below shows how far over — and which filter removes it.
See the measurement ↓Lead is well under the limit
90th-percentile lead is 0.0 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓1 violation in the last five years
Recent compliance history is the best predictor of future problems — the year-by-year record is below.
See the record ↓Oak Brook Terr's drinking water received a grade of B+ (80.1 out of 100), indicating good water quality. The city's 2 water systems serve approximately 1,440 residents using purchased surface water.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program. The system has 63 violations on record, including 7 health-based violations. 14 remain unresolved.
Oak Brook Terr ranks #563 out of 882 cities in Illinois for water quality, placing it below average in the state. The city draws from surface water sources, which are more susceptible to seasonal runoff and agricultural contamination, requiring extensive multi-barrier treatment including coagulation, filtration, and disinfection. As a small community water system, Oak Brook Terr may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Oak Brook Terr's water
Every contaminant flagged in Oak Brook Terr, on one shared scale: distance to its own legal limit. The red line is the limit — anything past it is out of compliance, and the closer a bar gets, the less headroom the system has.
Over Limit — EPA Action Level: 1.3 mg/L
Exceeds the EPA action level. Copper leaches from household plumbing — flush taps for 30 seconds before drinking, and consider a certified filter.Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 1.57 | 1.3 | mg/L | Inorganic | Over Limit |
Cities ranked by 90th-percentile lead PF PFAS in Illinois
Cities ranked by compounds detected Cu Copper in Illinois
Cities ranked by 90th-percentile copper
03Oak Brook Terr's ten-year track record
Each box is one year. A green check means no EPA violations; a numbered badge counts that year's violations — red if any were health-based, amber if they were monitoring or paperwork issues. The system has 63 violations on record, including 7 health-based violations. 14 remain unresolved.
8 of the last ten years were clean. The numbered years had EPA violations — red when any were health-based, amber when they were paperwork or missed-testing issues.
▼ Down 13 ppb since 1994. Latest reading: 0 ppb (2027) — 0% of the action level. Sampled at higher-risk homes (90th percentile).
1.6mg/L(2000)
One sampling round on record — 121% of the 1.3mg/L EPA action level. Sampled at higher-risk homes (90th percentile).
04Where Oak Brook Terr's water comes from
Oak Brook Terr's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
Purchased Surface Water
Rivers, lakes, or reservoirs — more exposed to runoff, agriculture, and seasonal swings than groundwater.
Wholesale supplier
Multi-barrier treatment: coagulation, sedimentation, filtration, and disinfection to meet EPA standards.
2 systems
2 water systems, operated under local government ownership.
1,440 people
Residents served across Oak Brook Terr's service area.
Surface water systems require multi-stage treatment including coagulation, sedimentation, filtration, and disinfection to meet EPA Safe Drinking Water Act standards. These sources can be impacted by seasonal changes, stormwater runoff, upstream agriculture, and industrial discharge. The system is operated by local government ownership and serves approximately 1,440 people through 2 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| OAKBROOK TERRACE | IL0430750 | 1,440 | Purchased Surface Water |
| YORK TOWNSHIP WATER SYSTEM | IL0430010 | 1,423 | Purchased Surface Water |
Water bodies near Oak Brook Terr
As a surface-water system, these water bodies may directly influence Oak Brook Terr's drinking water supply.
05Pressure on Oak Brook Terr's watershed
Outside forces that shape what reaches the treatment plant. None of these is a verdict on the tap by itself — but each adds pressure worth knowing about.
Flood & storm history
5 federal disaster declarations on record for DuPage County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Oak Brook Terr compares
Scores for nearby Illinois cities on one line, with the average marked.
dashed line = Illinois average (55/100)
Oak Brook Terr scores 80.1/100 — above the Illinois average of 55/100. It outscores 7 of 10 nearby cities. Full Illinois rankings →
35.2 / 100DAurora, IL
45.5 / 100FJoliet, IL
38.5 / 100BNaperville, IL
81.2 / 100FRockford, IL
38.4 / 100FKankakee, IL
42.6 / 100
Compare all cities in the county — grades, violations, and contaminant data side by side.→
07What to do at home
Steps matched to what testing actually found in Oak Brook Terr's water — not generic advice.
Filter drinking & cooking water
NSF-certified water filter. Copper exceeds the EPA action level of 1.3 mg/L
Compare tested filters →Read your utility's annual report
Every utility must publish a yearly Consumer Confidence Report with its own testing results. It pairs well with the independent data on this page.
How to read a CCR →Watch for Oak Brook Terr alerts
This area has a history of flood declarations — after severe weather, watch for boil-water advisories from the utility, and check the live alerts on this page.
All water alerts →Frequently asked questions
Is Oak Brook Terr, IL tap water safe to drink?
Oak Brook Terr's water quality earned a grade of B+ (80.1/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #563 out of 882 cities tested in Illinois.
What contaminants are in Oak Brook Terr's water?
Lead was measured at 0.0 ppb (90th percentile). 63 violations are on record.
How is Oak Brook Terr's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Oak Brook Terr?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Oak Brook Terr's water come from?
Oak Brook Terr's water is sourced from Purchased surface water. The city has 2 water systems serving approximately 1,440 residents.
What health violations has Oak Brook Terr's water system had?
Oak Brook Terr has 7 health-based violations on record. The most recent violation was recorded in July 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 14 violations remain unresolved.
How does Oak Brook Terr's water compare to other cities?
Oak Brook Terr ranks #563 out of 882 cities in Illinois (better than 36% of state cities) and #7924 out of 15382 cities nationally (49th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.