01The verdict: is Colchester water safe?
Colchester's tap water meets most EPA standards but has areas that warrant attention. With a grade of B+ (84/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 2 water systems serve approximately 1,395 residents using surface water (rivers, lakes, or reservoirs).
Copper is over its legal limit
Measured at 2.33 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 ↓2 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 ↓Colchester's drinking water received a grade of B+ (84 out of 100), indicating good water quality. The city's 2 water systems serve approximately 1,395 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 33 violations on record, including 23 health-based violations. 2 remain unresolved.
Colchester ranks #424 out of 882 cities in Illinois for water quality, placing it mid-range in the state. Colchester 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, Colchester may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
02What's in Colchester's water
Every contaminant flagged in Colchester, 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. | 2.33 | 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
03Colchester'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 33 violations on record, including 23 health-based violations. 2 remain unresolved.
9 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 1993. Latest reading: 0 ppb (2025) — 0% of the action level. Sampled at higher-risk homes (90th percentile).
▲ Up 0.64 mg/L since 2008. The latest reading (2.3 mg/L, 2009) is over the action level. Sampled at higher-risk homes (90th percentile).
04Where Colchester's water comes from
Colchester 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, operated under local government ownership.
1,395 people
Residents served across Colchester's service area.
Water quality depends on both the wholesaler's treatment standards and the condition of Colchester'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 1,395 people through 2 water systems.
| System name | PWSID | Population | Source |
|---|---|---|---|
| WEST PRAIRIE WATER CO-OP | IL1090030 | 2,395 | Purchased Groundwater |
| COLCHESTER | IL1090200 | 1,395 | Purchased Surface Water |
05Pressure on Colchester'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.
Industrial discharge
1 facility within 10 miles reported 0 lb released to surface water in the latest EPA Toxics Release Inventory. Proximity doesn't equal tap contamination — treatment and hydrology decide — but it's pressure on the watershed.
Flood & storm history
2 federal disaster declarations on record for McDonough County. Flooding and severe storms can overwhelm treatment plants, cause sewage overflows, and push runoff into supplies.
06How Colchester compares
Scores for nearby Illinois cities on one line, with the average marked.
dashed line = Illinois average (55/100)
Colchester scores 84/100 — above the Illinois average of 55/100. It outscores 10 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 Colchester's water — not generic advice.
Filter drinking & cooking water
Basic carbon filter for extra protection. 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 Colchester 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 Colchester, IL tap water safe to drink?
Colchester's water quality earned a grade of B+ (84/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #424 out of 882 cities tested in Illinois.
What contaminants are in Colchester's water?
Lead was measured at 0.0 ppb (90th percentile). 33 violations are on record.
How is Colchester'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 Colchester?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Colchester's water come from?
Colchester's water is sourced from Purchased surface water. The city has 2 water systems serving approximately 1,395 residents.
What health violations has Colchester's water system had?
Colchester has 23 health-based violations on record. The most recent violation was recorded in October 2021. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 2 violations remain unresolved.
How does Colchester's water compare to other cities?
Colchester ranks #424 out of 882 cities in Illinois (better than 52% of state cities) and #6106 out of 15382 cities nationally (60th percentile). The grade of B+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.