Is Thomson, IL Tap Water Safe to Drink?
Graded A-, with 2 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
88.7/100
waterverge.com Thomson, IL — Water Quality Report
Thomson's drinking water received a grade of A- (88.7 out of 100), indicating good water quality. The city's 2 water systems serve approximately 2,746 residents using purchased ground water.
Lead levels were measured at 0.6 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 7 violations on record, including 1 health-based violation. 2 remain unresolved.
What to know about Thomson's water
Thomson ranks #207 out of 891 cities in Illinois for water quality, placing it above average in the state.
Thomson 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, Thomson may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Thomson, IL water safe to drink?
Thomson's tap water meets most EPA standards but has areas that warrant attention. With a grade of A- (88.7/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 2 water systems serve approximately 2,746 residents using groundwater (wells).
Recent water quality updates for Thomson
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Thomson's water quality assessment. Grade: A- (88.7/100).
Contaminants: LEAD AND COPPER RULE REVISIONS.
Contaminants: Combined Radium (-226 and -228).
Contaminants: Combined Radium (-226 and -228).
Federal disaster declaration (FEMA DR-4461). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4116). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Thomson's water supply.
Well within EPA limits.
Violation history
Thomson's water system has 7 total violations on record, including 1 health-based violation. 2 remain unresolved. 3 violations were issued in the last 5 years.
Flood & environmental risk
Carroll County has experienced 8 federally declared disasters since 1969. 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 Mississippi River, Beaver Slough At 3Rd Street At Clinton.
Where does Thomson's water come from?
Thomson's drinking water comes from groundwater (wells), supplied by 2 water systems serving approximately 2,746 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Mississippi River (river), Beaver Slough At 3Rd Street At Clinton (river).
What Thomson residents can do
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.
Thomson'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 Thomson
Industrial polluters nearby
Reported releases to surface water by facilities near Thomson, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
ELKAY PLUMBING PRODUCTS CO SAVANNA, IL61074 | — | — | 7.4 mi |
METFORM CORP EXTRUSION SCIENCE PRODUCTS SAVANNA, IL61074 | — | — | 7.3 mi |
METFORM L.L.C. HOT FORMED PRODUCTS PLANT SAVANNA, IL61074 | — | — | 4.0 mi |
POWERLAB INC SAVANNA, IL61074 | — | — | 5.8 mi |
AGRI-KING INC. FULTON, IL61252 | — | — | 9.2 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Carroll County has experienced 8 federally declared disasters since 1969. 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. | 0.6 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Thomson compares by contaminant
Explore where Thomson ranks among all Illinois cities for specific contaminants.
Water source & infrastructure
Where Thomson's water comes from
Thomson purchases its water supply from a regional wholesale provider rather than treating raw water directly.
Water quality depends on both the wholesaler's treatment standards and the condition of Thomson'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 federal ownership and serves approximately 2,746 people through 2 water systems.
Water bodies near Thomson
Thomson is located near 2 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Thomson
| System Name | PWSID | Population | Source |
|---|---|---|---|
| THOMSON MAXIMUM SECURITY CENTER | IL0150030 | 2,166 | GWP |
| THOMSON | IL0150350 | 580 | GW |
How Thomson compares
Full Illinois rankings →Thomson's score of 88.7/100 is above the average of 56/100 among major Illinois cities. It outscores 9 of 10 nearby cities.
Nearby cities
View Illinois rankings →About Thomson, IL
Wikipedia →Thomson is a village along Illinois Route 84 near the Mississippi River in Carroll County, Illinois, United States. As of the 2020 census, Thomson had a population of 1,610. Just north of the village is the United States Penitentiary, Thomson, a mostly-unused former state prison, purchased by the Federal Bureau of Prisons in 2012. Currently USP Thomson houses over 100 low-security inmates as it remodels to federal maximum-security standards.
Learn more about your water
Guides and resources related to Thomson's water quality findings.
Explore water quality across Carroll
Frequently asked questions
Is Thomson, IL tap water safe to drink?
Thomson's water quality earned a grade of A- (88.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #207 out of 891 cities tested in Illinois.
What contaminants are in Thomson's water?
Lead was measured at 0.6 ppb (90th percentile). 7 violations are on record.
How is Thomson'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 Thomson?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Thomson's water come from?
Thomson's water is sourced from Purchased ground water. The city has 2 water systems serving approximately 2,746 residents.
What health violations has Thomson's water system had?
Thomson has 1 health-based violation 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. 2 violations remain unresolved.
Is Thomson's groundwater at risk of contamination?
Thomson 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 7 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 Thomson's water compare to other cities?
Thomson ranks #207 out of 891 cities in Illinois (better than 77% of state cities) and #3295 out of 15744 cities nationally (79th percentile). The grade of A- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.