01The verdict: is Illiopolis water safe?
Illiopolis's drinking water has significant quality concerns based on EPA testing data. With a grade of B- (72.8/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 2 water systems serve approximately 1,037 residents using groundwater (wells).
8 unresolved violations on record
EPA records show open compliance items for this system. Most are administrative, but unresolved items are worth watching.
See what was cited ↓Lead is well under the limit
90th-percentile lead is 4.2 ppb — beneath the 15 ppb federal action level and under the 5 ppb watch threshold.
See the trend ↓12 violations 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 ↓Illiopolis's drinking water received a grade of B- (72.8 out of 100), indicating fair water quality. The city's 2 water systems serve approximately 1,037 residents using purchased ground water.
Lead levels were measured at 4.2 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 20 violations on record, including 5 health-based violations. 8 remain unresolved.
Illiopolis ranks #701 out of 882 cities in Illinois for water quality, placing it among the lowest-rated in the state. Illiopolis purchases its water from a regional wholesaler, meaning quality depends on both the supplier's treatment and the local distribution system's condition. As a small community water system, Illiopolis may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities. The system has seen 12 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
02What's in Illiopolis's water
Every contaminant flagged in Illiopolis, 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.
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. | 4.2 | 15 | ppb | Inorganic | Safe |
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
03Illiopolis'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 20 violations on record, including 5 health-based violations. 8 remain unresolved.
3 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 0 ppb since 1993. Latest reading: 0 ppb (2025) — 0% of the action level. Sampled at higher-risk homes (90th percentile).
04Where Illiopolis's water comes from
Illiopolis purchases its water supply from a regional wholesale provider rather than treating raw water directly.
Purchased Groundwater
Water is bought from a regional wholesaler; quality starts at the supplier's intake and treatment.
Wholesale supplier
Primary treatment happens at the wholesaler; the local utility maintains disinfectant residual in its pipes.
2 systems
2 water systems (1 wholesaler), operated under local government ownership.
1,037 people
Residents served across Illiopolis's service area.
Water quality depends on both the wholesaler's treatment standards and the condition of Illiopolis's local distribution pipes and storage facilities. Purchased water systems are common in suburban areas and smaller communities that lack the infrastructure for independent treatment. The system is operated by local government ownership and serves approximately 1,037 people through 2 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| ILLIOPOLIS | IL1670550 | 1,037 | Purchased Groundwater |
| UNITED REGIONAL WATER COOP | IL1670260 | 25 | Groundwater |
Water bodies near Illiopolis
These water bodies shape the regional watershed and can indirectly affect groundwater quality.
05Pressure on Illiopolis'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
2 federal disaster declarations on record for Sangamon County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Illiopolis compares
Scores for nearby Illinois cities on one line, with the average marked.
dashed line = Illinois average (55/100)
Illiopolis scores 72.8/100 — 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 Illiopolis's water — not generic advice.
A basic carbon filter still helps
Illiopolis's water meets federal standards, but a simple carbon filter improves taste and adds a margin of safety against short-term issues.
Compare tested filters →Flush taps & check your service line
Lead leaches from pipes as water sits. Run cold water 30 seconds before drinking (especially mornings), and ask the utility whether your address still has a lead service line.
Lead risks explained →Watch for Illiopolis alerts
We refresh EPA data monthly and surface new violations, advisories, and boil-water notices for your county on this page.
All water alerts →Frequently asked questions
Is Illiopolis, IL tap water safe to drink?
Illiopolis's water quality earned a grade of B- (72.8/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #701 out of 882 cities tested in Illinois.
What contaminants are in Illiopolis's water?
Lead was measured at 4.2 ppb (90th percentile). 20 violations are on record.
How is Illiopolis'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 Illiopolis?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Illiopolis's water come from?
Illiopolis's water is sourced from Purchased ground water. The city has 2 water systems serving approximately 1,037 residents.
What health violations has Illiopolis's water system had?
Illiopolis has 5 health-based violations on record. The most recent violation was recorded in April 2025. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 8 violations remain unresolved.
Is Illiopolis's groundwater at risk of contamination?
Illiopolis 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 20 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 Illiopolis's water compare to other cities?
Illiopolis ranks #701 out of 882 cities in Illinois (better than 21% of state cities) and #10108 out of 15382 cities nationally (34th percentile). The grade of B- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.