Wyoming Water Quality Report: 790 Water-System Violations Mapped to 48 ZIPs
98 water systems · 48 ZIP codes · 790 violations
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO
ZipCheckup tracks EPA drinking-water compliance for 98 public water systems serving 48 ZIP codes in Wyoming. The state record shows 790 EPA violations, 64 health-based.
City Water Quality Map: Wyoming
Each circle represents a city. Size indicates population, color indicates water quality grade. Tap a circle for details.
Cities with Most Violations in Wyoming
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Jackson | 196 | 4 | 17,458 | Details → | |
| 2 | Wilson | 188 | 4 | 2,807 | Details → | |
| 3 | Newcastle | 162 | 3 | 5,411 | Details → | |
| 4 | Riverton | 88 | 4 | 18,946 | Details → | |
| 5 | Rawlins | 38 | 1 | 8,267 | Details → | |
| 6 | Cheyenne | 12 | 8 | 95,110 | Details → | |
| 7 | Kemmerer | 10 | 1 | 3,576 | Details → | |
| 8 | Frontier | 10 | 1 | 3,348 | Details → | |
| 9 | Diamondville | 10 | 1 | 603 | Details → | |
| 10 | Casper | 8 | 6 | 73,288 | Details → |
Most Common Contaminants in Wyoming
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 45 | 15 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 22 | 11 | Yes |
| Consumer Confidence Rule | Reporting | 22 | 10 | No |
| Lead and Copper Rule | Treatment Technique | 20 | 11 | No |
| Arsenic | Inorganic | 14 | 5 | No |
| Barium | Inorganic | 13 | 5 | No |
| Cadmium | Inorganic | 13 | 5 | No |
| Chromium | Inorganic | 13 | 5 | No |
| Cyanide | Inorganic | 13 | 5 | No |
| Fluoride | Inorganic | 13 | 5 | No |
Water Quality Overview
Wyoming has 98 community water systems represented across 48 directly mapped ZIP records. The associated city records cover approximately 499,669 people. The available records contain 790 EPA violations, including 64 health-based violations.
Health-based violations account for 8% of all violations in Wyoming. 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 | 64 | 8.1% |
| Monitoring/Reporting | 726 | 91.9% |
| Total | 790 | 100% |
Health-based violations are MCL, MRDL (disinfectant) and treatment-technique violations. 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 Wyoming have the highest number of EPA violations:
| Rank | City | Violations | Water Systems | Population |
|---|---|---|---|---|
| 1 | Jackson | 196 | 4 | 17,458 |
| 2 | Wilson | 188 | 4 | 2,807 |
| 3 | Newcastle | 162 | 3 | 5,411 |
| 4 | Riverton | 88 | 4 | 18,946 |
| 5 | Rawlins | 38 | 1 | 8,267 |
| 6 | Cheyenne | 12 | 8 | 95,110 |
| 7 | Kemmerer | 10 | 1 | 3,576 |
| 8 | Frontier | 10 | 1 | 3,348 |
| 9 | Diamondville | 10 | 1 | 603 |
| 10 | Casper | 8 | 6 | 73,288 |
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 Wyoming:
| Year | Health-based violations |
|---|---|
| 2021 | 6 |
| 2022 | 4 |
| 2023 | 7 |
| 2024 | 34 |
| 2025 | 10 |
Health-based violations have increased from 6 in 2021 to 10 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 Wyoming water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 45 | 15 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 22 | 11 | Yes |
| Consumer Confidence Rule | Reporting | 22 | 10 | No |
| Lead and Copper Rule | Treatment Technique | 20 | 11 | No |
| Arsenic | Inorganic | 14 | 5 | No |
| Barium | Inorganic | 13 | 5 | No |
| Cadmium | Inorganic | 13 | 5 | No |
| Chromium | Inorganic | 13 | 5 | No |
| Cyanide | Inorganic | 13 | 5 | No |
| Fluoride | Inorganic | 13 | 5 | No |
How to Check Your Water in Wyoming
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 enforcement actions against water systems in Wyoming. 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 are EPA violations of a Maximum Contaminant Level (MCL), a Maximum Residual Disinfectant Level (MRDL) or a required treatment technique - the enforceable standards designed to protect human health. Wyoming has 64 such violations across its water systems. Not all violations cause illness; review each violation type and duration to understand possible health implications.
Understanding water quality grades
ZipCheckup grades water systems from A to F based on EPA violation history, contaminant levels, and system compliance. Grades summarize ZipCheckup's scoring inputs; review the underlying records for specific 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 Wyoming?
Records for 98 community water systems mapped to ZIPs in Wyoming show 790 reported violations, including 64 health-based. Water quality varies by city and ZIP code - check your specific location for detailed results.
How many violations are on record for water systems serving Wyoming?
Wyoming has 790 EPA violations on record across 48 ZIP codes; 64 are classified as health-based violations. The remainder are monitoring or reporting violations.
Which city in Wyoming has the worst water quality?
Jackson, WY has the most recorded EPA violations (196) among the cities with mapped water systems in Wyoming in our data. Check your water supplier's report and test your tap water for the most accurate picture of your local water quality.
Which city in Wyoming has the best water quality?
Violation records vary by water system across Wyoming. Check individual city reports for details.
What contaminants are found in Wyoming drinking water?
EPA regulates over 90 drinking-water contaminants nationally; water systems in Wyoming monitor those applicable to each system, which can include lead, copper, nitrate, disinfection byproducts, and bacteria. The most common violations vary by region - check your ZIP code for contaminant-specific data.