Wisconsin Water Quality Report: 3,023 Violations Across 466 ZIPs
916 water systems · 466 ZIP codes · 3,023 violations · Updated
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO Last verified:
ZipCheckup tracks EPA drinking-water compliance for 916 public water systems serving 466 ZIP codes in Wisconsin. The state record shows 3,023 EPA violations, 766 health-based.
City Water Quality Map: Wisconsin
Each circle represents a city. Size indicates population, color indicates water quality grade. Tap a circle for details.
Violation Trend
EPA violations across all water systems in Wisconsin.
Cities with Most Violations in Wisconsin
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Waukesha | 144 | 9 | 94,161 | Details → | |
| 2 | Pewaukee | 142 | 5 | 26,652 | Details → | |
| 3 | New Berlin | 78 | 4 | 40,213 | Details → | |
| 4 | Wales | 76 | 3 | 3,073 | Details → | |
| 5 | West Bend | 71 | 7 | 49,524 | Details → | |
| 6 | Delavan | 69 | 5 | 16,056 | Details → | |
| 7 | Kewaskum | 67 | 3 | 8,223 | Details → | |
| 8 | Lake Geneva | 63 | 5 | 18,440 | Details → | |
| 9 | Madison | 62 | 16 | 308,771 | Details → | |
| 10 | Racine | 50 | 6 | 127,813 | Details → |
Most Common Contaminants in Wisconsin
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Lead and Copper Rule | Treatment Technique | 589 | 238 | No |
| Stage 2 DBP Rule | Treatment Technique | 352 | 225 | Yes |
| Gross Beta | Radionuclides | 316 | 46 | Yes |
| Gross Alpha | Radionuclides | 313 | 36 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 302 | 157 | Yes |
| Surface Water Treatment Rule | Treatment Technique | 244 | 106 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 98 | 81 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 87 | 74 | Yes |
| Lead | Inorganic | 47 | 38 | Yes |
| Radium-228 | Radionuclides | 42 | 27 | No |
Water Quality Overview
Wisconsin has 916 community water systems represented across 466 directly mapped ZIP records. The associated city records cover approximately 5,445,157 people. The available records contain 3,023 EPA violations, including 766 health-based violations.
Health-based violations account for 25% of all violations in Wisconsin. These violations indicate contaminant levels that may pose direct risks to human health, as opposed to monitoring or reporting failures.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 766 | 25.3% |
| Monitoring/Reporting | 2,257 | 74.7% |
| Total | 3,023 | 100% |
Health-based violations indicate contaminant levels exceeding EPA Maximum Contaminant Levels (MCLs). Monitoring violations indicate failures to test or report - these do not necessarily mean unsafe water, but they mean the water was not properly verified.
Cities with Most Violations
The following cities in Wisconsin have the highest number of EPA violations:
| Rank | City | Violations | Water Systems | Population |
|---|---|---|---|---|
| 1 | Waukesha | 144 | 9 | 94,161 |
| 2 | Pewaukee | 142 | 5 | 26,652 |
| 3 | New Berlin | 78 | 4 | 40,213 |
| 4 | Wales | 76 | 3 | 3,073 |
| 5 | West Bend | 71 | 7 | 49,524 |
| 6 | Delavan | 69 | 5 | 16,056 |
| 7 | Kewaskum | 67 | 3 | 8,223 |
| 8 | Lake Geneva | 63 | 5 | 18,440 |
| 9 | Madison | 62 | 16 | 308,771 |
| 10 | Racine | 50 | 6 | 127,813 |
Violation counts are cumulative across all water systems serving each city. Higher counts may reflect larger systems with more monitoring requirements, not necessarily worse water quality.
Violation Trend Over Time
Year-by-year EPA violations recorded across all water systems in Wisconsin:
| Year | Total Violations | Health-Based |
|---|---|---|
| 2021 | 30 | 30 |
| 2022 | 78 | 78 |
| 2023 | 122 | 122 |
| 2024 | 436 | 436 |
| 2025 | 105 | 105 |
Violations have increased from 30 in 2021 to 105 in 2025. This trend warrants monitoring and may reflect expanded testing requirements rather than worsening quality.
Most Common Contaminants
The following contaminants have caused the most violations across Wisconsin water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Lead and Copper Rule | Treatment Technique | 589 | 238 | No |
| Stage 2 DBP Rule | Treatment Technique | 352 | 225 | Yes |
| Gross Beta | Radionuclides | 316 | 46 | Yes |
| Gross Alpha | Radionuclides | 313 | 36 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 302 | 157 | Yes |
| Surface Water Treatment Rule | Treatment Technique | 244 | 106 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 98 | 81 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 87 | 74 | Yes |
| Lead | Inorganic | 47 | 38 | Yes |
| Radium-228 | Radionuclides | 42 | 27 | No |
How to Check Your Water in Wisconsin
Enter your ZIP code on ZipCheckup for detailed water-system data including contaminant levels and violation history; the separate Home Safety Score is a multi-source index
Request your CCR - every water utility must provide an annual Consumer Confidence Report
Get a home test - certified kits ($20-$50) or professional lab tests ($150-$400)
Consider filtration - NSF-certified filters can address specific contaminants found in your area
EPA Enforcement
The EPA and state regulators have taken 3,157 enforcement actions against water systems in Wisconsin. Enforcement actions range from compliance assistance to formal orders and penalties.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Updated daily.
What are EPA violations?
Health-based violations mean a contaminant was detected above the EPA's Maximum Contaminant Level (MCL) - the legal limit designed to protect human health. Wisconsin has 766 such violations across its water systems. Not all violations cause illness, but repeated exceedances increase risk, especially for children and immunocompromised individuals.
Understanding water quality grades
ZipCheckup grades water systems from A to F based on EPA violation history, contaminant levels, and system compliance. Grade A means few or no violations; Grade F indicates persistent or serious issues. Grades are calculated per ZIP code and aggregated at the city, county, and state level.
Wondering about your tap water?
Water quality varies by ZIP code. Enter yours to see contaminant data, violations, and filtration recommendations specific to your area.
Check Your ZIP Code Water Quality →Frequently Asked Questions
Is the tap water safe to drink in Wisconsin?
Wisconsin has 916 community water systems with 3,023 recorded EPA violations, including 766 health-based. Water quality varies by city and ZIP code - check your specific location for detailed results.
How many water violations does Wisconsin have?
Wisconsin has 3,023 total EPA violations across 466 ZIP codes. 766 are health-based violations that indicate contaminant levels potentially harmful to human health. The remainder are monitoring or reporting violations.
Which city in Wisconsin has the worst water quality?
Waukesha, WI has the most EPA violations among major cities in Wisconsin with 144 recorded violations. Check individual ZIP codes for the most accurate picture of your local water quality.
Which city in Wisconsin has the best water quality?
Several cities in Wisconsin maintain excellent EPA compliance. Check individual city reports for details.
What contaminants are found in Wisconsin drinking water?
Wisconsin water systems are monitored for over 90 EPA-regulated contaminants including lead, copper, nitrates, disinfection byproducts, and bacteria. The most common violations vary by region - check your ZIP code for contaminant-specific data.