Is Thornton, IL Tap Water Safe to Drink?
Graded B, with 5 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
79.8/100
waterverge.com Thornton, IL — Water Quality Report
Thornton's drinking water received a grade of B (79.8 out of 100), indicating good water quality. The city's 1 water system serves approximately 2,333 residents using purchased surface water.
Lead levels were measured at 4.0 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 6 violations on record, including 0 health-based violations. 5 remain unresolved.
What to know about Thornton's water
Thornton ranks #577 out of 891 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, Thornton may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Thornton, IL water safe to drink?
Thornton's drinking water has significant quality concerns based on EPA testing data. With a grade of B (79.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 2,333 residents using surface water (rivers, lakes, or reservoirs).
Recent water quality updates for Thornton
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Thornton's water quality assessment. Grade: B (79.8/100).
Contaminants: Consumer Confidence Rule.
Federal disaster declaration (FEMA DR-4819). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4749). Flood event — may have impacted local water infrastructure.
Contaminants: Consumer Confidence Rule.
Contaminants: Consumer Confidence Rule.
Key contaminant findings
Based on the most recent EPA sampling data for Thornton's water supply.
Well within EPA limits.
Violation history
Thornton's water system has 6 total violations on record, including 0 health-based violations. 5 remain unresolved. 3 violations were issued in the last 5 years.
Flood & environmental risk
Cook County has experienced 9 federally declared disasters since 1972. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Pullman Creek, Indiana Harbor Canal, Little Calumet River, Plum Creek, Hart Ditch.
Where does Thornton's water come from?
Thornton's drinking water comes from surface water (rivers, lakes, or reservoirs), supplied by 1 water system serving approximately 2,333 people. Surface water sources are more susceptible to contamination from runoff, industrial discharge, and algal blooms, requiring extensive treatment. Nearby water bodies include Pullman Creek (river), Indiana Harbor Canal (stream), Little Calumet River (river), Plum Creek (river), Hart Ditch (stream).
What Thornton residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Thornton's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Run cold water for 30 seconds before drinking, especially in the morning. Lead and copper leach from household plumbing when water sits in pipes.
Thornton's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Top industrial polluters within 10 miles of Thornton
Industrial polluters nearby
Reported releases to surface water by facilities near Thornton, ranked by pounds discharged annually.
Total reported releases to surface water: 1,195,113 lbs
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
BP PRODUCTS NA WHITING BUSINESS UNIT WHITING, IN46394 | Nitrate compounds (water dissociable; reportable only when in aqueous solution) | 1,002,622 | 9.3 mi |
CARGILL TEXTURIZING SOLUTIONS HAMMOND, IN46320 | Nitrate compounds (water dissociable; reportable only when in aqueous solution) | 187,428 | 9.9 mi |
CLEVELAND-CLIFFS STEEL LLC EAST CHICAGO, IN46312 | Zinc compounds | 4,872 | 9.9 mi |
CID RECYCLING & DISPOSAL FACILITY CALUMET CITY, IL60409 | Ammonia | 101 | 4.3 mi |
CLEVELAND-CLIFFS RIVERDALE LLC RIVERDALE, IL60827 | Manganese And Manganese Compounds | 90 | 5.1 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Thornton
Superfund sites nearby
Federally tracked hazardous-waste sites on the EPA National Priorities List. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
- ESTECH GENERAL CHEMICAL COMPANY6.1 mi
- SCHROUD PROPERTY7.3 mi
- LAKE CALUMET CLUSTER7.7 mi
- ACME STEEL COKE PLANT8.5 mi
- U S SMELTER AND LEAD REFINERY INC8.5 mi
+ 3 more sites
Source: EPA Superfund National Priorities List
Flood & disaster history
Cook County has experienced 9 federally declared disasters since 1972. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
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. | 4.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Thornton compares by contaminant
Explore where Thornton ranks among all Illinois cities for specific contaminants.
Water source & infrastructure
Where Thornton's water comes from
Thornton's drinking water comes primarily from surface water sources such as rivers, lakes, or reservoirs.
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 2,333 people through 1 water system.
Water bodies near Thornton
Thornton is located near 5 notable water bodies. As a surface water system, these water bodies may directly influence the city's drinking water supply.
Water systems serving Thornton
| System Name | PWSID | Population | Source |
|---|---|---|---|
| THORNTON | IL0313090 | 2,333 | SWP |
How Thornton compares
Full Illinois rankings →Thornton's score of 79.8/100 is above the average of 56/100 among major Illinois cities. It outscores 7 of 10 nearby cities.
Nearby cities
View Illinois rankings →About Thornton, IL
Wikipedia →Thornton is a village in Cook County, Illinois, United States, and a south suburb of Chicago. The population was 2,386 at the 2020 census. Thornton is home to the Thornton Quarry, one of the largest quarries in the world.
Learn more about your water
Guides and resources related to Thornton's water quality findings.
Explore water quality across Cook
Frequently asked questions
Is Thornton, IL tap water safe to drink?
Thornton's water quality earned a grade of B (79.8/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #577 out of 891 cities tested in Illinois.
What contaminants are in Thornton's water?
Lead was measured at 4.0 ppb (90th percentile). 6 violations are on record.
How is Thornton'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 Thornton?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Thornton's water come from?
Thornton's water is sourced from Purchased surface water. The city has 1 water system serving approximately 2,333 residents.
How does Thornton's water compare to other cities?
Thornton ranks #577 out of 891 cities in Illinois (better than 35% of state cities) and #8133 out of 15744 cities nationally (48th percentile). The grade of B reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Thornton's small water system affect quality?
Thornton's system serves approximately 2,333 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 6 violations on record.