Is Onarga, IL Tap Water Safe to Drink?
Graded B+ — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
80/100
waterverge.com Onarga, IL — Water Quality Report
Onarga's drinking water received a grade of B+ (80 out of 100), indicating good water quality. The city's 1 water system serves approximately 1,409 residents using groundwater.
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 10 violations on record, including 1 health-based violation. 6 remain unresolved.
What to know about Onarga's water
Onarga ranks #571 out of 891 cities in Illinois for water quality, placing it below average in the state.
Onarga relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
As a small community water system, Onarga may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Onarga, IL water safe to drink?
Onarga's drinking water has significant quality concerns based on EPA testing data. With a grade of B+ (80/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 1,409 residents using groundwater (wells).
Recent water quality updates for Onarga
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Onarga's water quality assessment. Grade: B+ (80/100).
Contaminants: Public Notice.
Contaminants: Revised Total Coliform Rule.
Contaminants: Chlorine.
Federal disaster declaration (FEMA DR-3230). Hurricane event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Onarga's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Onarga's water system has 10 total violations on record, including 1 health-based violation. 6 remain unresolved. 5 violations were issued in the last 5 years.
Flood & environmental risk
Iroquois County has experienced 1 federally declared disaster since 2005. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies.
Where does Onarga's water come from?
Onarga's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 1,409 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate.
What Onarga residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Onarga'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.
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 Onarga
Industrial polluters nearby
Reported releases to surface water by facilities near Onarga, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
INCOBRASA INDUSTRIES LTD GILMAN, IL60938 | — | — | 2.5 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Iroquois County has experienced 1 federally declared disaster since 2005. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Onarga's water supply, we recommend the following filter types.
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. | 1.40 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level (90th percentile)
Latest reading: 1.400 mg/L (2021)
EPA action level: 1.3 mg/L
See how Onarga compares by contaminant
Explore where Onarga ranks among all Illinois cities for specific contaminants.
Water source & infrastructure
Where Onarga's water comes from
Onarga's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by local government ownership and serves approximately 1,409 people through 1 water system.
Water systems serving Onarga
| System Name | PWSID | Population | Source |
|---|---|---|---|
| ONARGA | IL0750700 | 1,409 | GW |
How Onarga compares
Full Illinois rankings →Onarga's score of 80/100 is above the average of 56/100 among major Illinois cities. It outscores 7 of 10 nearby cities.
Nearby cities
View Illinois rankings →About Onarga, IL
Wikipedia →Onarga is a village in Onarga Township, Iroquois County, Illinois, United States. The population was 1,333 at the 2020 census.
Learn more about your water
Guides and resources related to Onarga's water quality findings.
Explore water quality across Iroquois
Frequently asked questions
Is Onarga, IL tap water safe to drink?
Onarga's water quality earned a grade of B+ (80/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #571 out of 891 cities tested in Illinois.
What contaminants are in Onarga's water?
Lead was measured at 0.0 ppb (90th percentile). 10 violations are on record.
How is Onarga'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 Onarga?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Onarga's water come from?
Onarga's water is sourced from Groundwater. The city has 1 water system serving approximately 1,409 residents.
What health violations has Onarga's water system had?
Onarga has 1 health-based violation on record. The most recent violation was recorded in October 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 6 violations remain unresolved.
Is Onarga's groundwater at risk of contamination?
Onarga uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 10 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Onarga's water compare to other cities?
Onarga ranks #571 out of 891 cities in Illinois (better than 36% of state cities) and #8067 out of 15744 cities nationally (49th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Onarga's small water system affect quality?
Onarga's system serves approximately 1,409 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 10 violations on record.