D23/100
Mason City Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 2,558 residents · Illinois
What's In Mason City's Tap Water?
1
Contaminants Tested
0
Exceed EPA Limits
0
Above EPA Goals
EPA Violation History
1
Violation (last 5yr)
1
Unresolved
0
Health-Related
TIER 3Unresolved
Reporting Violation
This is a paperwork/process violation — it does not mean a contaminant was detected at unsafe levels.
When: July 2, 2025Rule: Ground Water RuleEnforcement: Informal — resolved cooperativelyVerify on EPA.gov
Understanding violation severity
Tier 1Urgent health risk. Utility must notify all customers within 24 hours.Tier 2Important health or treatment issue. Customers notified within 30 days.Tier 3Administrative or monitoring issue. Reported in the annual water quality report.
Source: EPA Safe Drinking Water Information System (SDWIS) · Updated quarterly
Water Utility Details
MASON CITY
Population Served
2,558
Water Source
Groundwater
System ID
IL1250350
Frequently Asked Questions About Mason City Water
Is Mason City tap water safe to drink?
Mason City, Illinois tap water receives a grade of D (23/100), which is considered poor. 0 contaminant(s) exceed EPA maximum contaminant levels and 17 violation(s) are on record. Residents should consider using an NSF-certified water filter to reduce contaminant exposure.
What contaminants are in Mason City's water?
1 contaminants were tested in Mason City's water supply. No contaminants exceed EPA legal limits (MCLs) or health goals (MCLGs), which is a positive indicator of water quality.
Does Mason City have any water quality violations?
Yes, Mason City has 17 EPA violation(s) on record, with the most recent in 2025. Violation types include RPT, MCL, MR. 15 of these are health-based violations, which are the most serious category.
Do I need a water filter in Mason City?
Mason City water meets EPA standards, so a filter is not strictly necessary. However, some residents prefer the added security of a water filter. EPA health goals (MCLGs) are stricter than legal limits and are set at levels with zero expected health risk. All contaminants are within health goals.
Where does Mason City's tap water come from?
Mason City's drinking water is sourced from groundwater and supplied by MASON CITY. The system serves approximately 2,558 people. Groundwater is pumped from underground aquifers, which often provides natural filtration.
How often is Mason City's water tested?
Under the Safe Drinking Water Act (SDWA), water utilities are required to regularly test for over 90 contaminants. Testing frequency varies by contaminant — some are tested monthly, others quarterly or annually. Mason City's water systems must report results to the EPA and publish an annual Consumer Confidence Report (CCR). The data on this page reflects the latest available EPA testing data.
How does Mason City's water compare to other cities in Illinois?
Mason City's water quality score of 23/100 earns a grade of D, which is considered poor. This is a concerning score that suggests significant water quality issues. Visit our Illinois state page to see how all cities in the state compare.
What should I do if I'm concerned about Mason City's water quality?
If you have concerns about Mason City's tap water, consider these steps: (1) Request your utility's annual Consumer Confidence Report for detailed local data. (2) Get your water independently tested through a state-certified laboratory. (3) Consider an NSF-certified water filter rated for the contaminants found in your area. (4) Contact your water utility (MASON CITY) with specific questions. (5) Report water quality issues to your state drinking water program or the EPA Safe Drinking Water Hotline at 800-426-4791.