Water Quality in Mason City, IA: 2 Violations — Grade C
Grade C · Score 61/100 · 1 water system · Updated 2026-05-03
Mason City's water has moderate compliance issues. Residents in affected areas should consider filtration.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
The compliance record maintained by the EPA for Mason City, IA documents 2 water violations — each tied to a specific public water system and assigned a violation category in the federal Safe Drinking Water dataset.
Water Quality by ZIP Code in Mason City
Water quality varies across Mason City's 2 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 50401 | C | 55 | 1 | 0 | View report → |
| 50402 | C | 66 | 1 | 0 | View report → |
Water Quality Overview
Mason City, Iowa receives a water quality grade of C with an overall score of 61 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
The 1 water system serving Mason City have accumulated 2 EPA violations (all monitoring/reporting type). These violations are tracked across 2 ZIP codes serving approximately 27,338 people.
What Grade C Means
A grade of C indicates moderate compliance issues. Mason City's water systems have some violations that warrant attention. While the water may still be safe for most people, residents in affected ZIP codes should consider additional testing or filtration.
Lead Levels
The average 90th percentile lead level across Mason City water systems is 0.0029 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
With 84% of homes built before 1986, Mason City has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Radon Risk
Mason City is in EPA Radon Zone 1 (High risk). The EPA recommends all homes in Zone 1 areas be tested for radon. Radon is the second leading cause of lung cancer after smoking.
Water Systems Serving Mason City
Mason City is served by 1 community water system regulated under the Safe Drinking Water Act. These systems collectively serve approximately 27,338 people across 2 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
The EPA has taken 8 enforcement actions against water systems serving Mason City. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Mason City
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
EPA Enforcement History
The EPA and state regulators have taken 4 enforcement actions against water systems serving Mason City. Recent actions:
| Date | Action Type |
|---|---|
| 2024-10-17 | State Order Extension |
| 2024-07-18 | State Informal Enforcement |
| 2024-07-18 | State Filed Judgment |
| 2024-07-08 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2024-10-17.
Mason City vs. Nearby Iowa Cities
How Mason City's water quality compares to similar cities in Iowa:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Mason City | C | 2 | 1 | 27,338 |
| Altoona | C | 3 | 2 | 27,130 |
| Spencer | C | 0 | 5 | 26,964 |
| Fort Dodge | F | 27 | 5 | 27,898 |
Common Questions About Mason City Water
These are the most common questions residents search for about water quality in Mason City, Iowa:
Is Mason City water hard or soft? Water hardness varies by source. Mason City's 1 water system uses a single source. Check your ZIP code report for specific hardness data.
Can I drink Mason City tap water? Mason City's water receives a grade of C (61/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Mason City? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
Mason City vs. Iowa Average
Understanding how Mason City compares to the broader Iowa average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within Mason City.
ZIP Codes in Mason City
Mason City spans 2 ZIP codes. The ZIP with the lowest water quality score is 50401. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.