Is Mason City, IL Tap Water Safe to Drink?
Graded A, with 1 unresolved violation on record. See what was cited — and what it means for your tap. What to do next ↓
90.7/100
waterverge.com Mason City, IL — Water Quality Report
Mason City's drinking water received a grade of A (90.7 out of 100), indicating excellent water quality. The city's 1 water system serves approximately 2,558 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 17 violations on record, including 15 health-based violations. 1 remains unresolved.
What to know about Mason City's water
Mason City ranks #123 out of 891 cities in Illinois for water quality, placing it above average in the state.
Mason City 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, Mason City may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Mason City, IL water safe to drink?
Mason City's tap water meets most EPA standards but has areas that warrant attention. With a grade of A (90.7/100), some contaminant levels or compliance issues suggest that residents may benefit from additional filtration. The city's 1 water system serves approximately 2,558 residents using groundwater (wells).
Recent water quality updates for Mason City
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Mason City's water quality assessment. Grade: A (90.7/100).
Contaminants: LEAD AND COPPER RULE REVISIONS.
Federal disaster declaration (FEMA DR-4116). Flood event — may have impacted local water infrastructure.
1 health-based. Contaminants: Arsenic.
1 health-based. Contaminants: Arsenic.
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 Mason City's water supply.
Well within EPA limits.
Violation history
Mason City's water system has 17 total violations on record, including 15 health-based violations. 1 remain unresolved. 1 violation was issued in the last 5 years.
Flood & environmental risk
Mason County has experienced 7 federally declared disasters since 1973. 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 Salt Creek.
Where does Mason City's water come from?
Mason City's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 2,558 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Salt Creek (river).
What Mason City 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.
Mason City'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 Mason City
Industrial polluters nearby
Reported releases to surface water by facilities near Mason City, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
DARLING INGREDIENTS INC MASON CITY, IL62664 | — | — | 0.6 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Flood & disaster history
Mason County has experienced 7 federally declared disasters since 1973. 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. | 0.0 | 15 | ppb | Inorganic | Safe |
Lead level trend (90th percentile)
See how Mason City compares by contaminant
Explore where Mason City ranks among all Illinois cities for specific contaminants.
Water source & infrastructure
Where Mason City's water comes from
Mason City'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 2,558 people through 1 water system.
Water bodies near Mason City
Mason City is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Mason City
| System Name | PWSID | Population | Source |
|---|---|---|---|
| MASON CITY | IL1250350 | 2,558 | GW |
How Mason City compares
Full Illinois rankings →Mason City's score of 90.7/100 is above the average of 56/100 among major Illinois cities. It outscores 9 of 10 nearby cities.
Nearby cities
View Illinois rankings →About Mason City, IL
Learn more about your water
Guides and resources related to Mason City's water quality findings.
Explore water quality across Mason
Frequently asked questions
Is Mason City, IL tap water safe to drink?
Mason City's water quality earned a grade of A (90.7/100). The water generally meets EPA standards and is considered safe for consumption. The city ranks #123 out of 891 cities tested in Illinois.
What contaminants are in Mason City's water?
Lead was measured at 0.0 ppb (90th percentile). 17 violations are on record.
How is Mason City'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 Mason City?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Mason City's water come from?
Mason City's water is sourced from Groundwater. The city has 1 water system serving approximately 2,558 residents.
What health violations has Mason City's water system had?
Mason City has 15 health-based violations 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. 1 violation remains unresolved.
Is Mason City's groundwater at risk of contamination?
Mason City 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 17 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 Mason City's water compare to other cities?
Mason City ranks #123 out of 891 cities in Illinois (better than 86% of state cities) and #2079 out of 15744 cities nationally (87th percentile). The grade of A reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Mason City's small water system affect quality?
Mason City's system serves approximately 2,558 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 17 violations on record.