Colorado Water Quality Report: 4,570 Violations Across 658 ZIPs
747 water systems · 658 ZIP codes · 4,570 violations · Updated 2026-05-31
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO Last verified: 2026-05-31
City Water Quality Map: Colorado
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 Colorado.
Cities with Most Violations in Colorado
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Denver | C | 207 | 5 | 1,350,703 | Details → |
| 2 | Aurora | D | 204 | 5 | 602,310 | Details → |
| 3 | Boulder | C | 192 | 5 | 169,750 | Details → |
| 4 | Colorado Springs | B | 165 | 5 | 547,861 | Details → |
| 5 | Steamboat Springs | C | 150 | 5 | 28,847 | Details → |
| 6 | Hotchkiss | C | 92 | 5 | 3,653 | Details → |
| 7 | Englewood | C | 91 | 5 | 100,054 | Details → |
| 8 | Fort Collins | C | 90 | 5 | 301,072 | Details → |
| 9 | Evergreen | D | 90 | 5 | 17,045 | Details → |
| 10 | Estes Park | C | 88 | 5 | 21,949 | Details → |
Most Common Contaminants in Colorado
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Lead and Copper Rule | Treatment Technique | 747 | 199 | No |
| E. coli | Microbiological | 531 | 183 | Yes |
| Fecal Coliform | Microbiological | 476 | 196 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 462 | 197 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 385 | 179 | Yes |
| Surface Water Treatment Rule | Treatment Technique | 219 | 154 | No |
| Gross Beta | Radionuclides | 218 | 45 | Yes |
| Revised Total Coliform Rule | Microbiological | 209 | 108 | No |
| Total Coliform | Microbiological | 124 | 94 | No |
| Combined Radium | Radionuclides | 98 | 85 | Yes |
Water Quality Overview
Colorado has 747 community water systems serving approximately 8,735,520 people across 658 ZIP codes. These systems have accumulated 4,570 EPA violations, including 671 health-based violations.
Health-based violations account for 15% of all violations in Colorado. 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 | 671 | 14.7% |
| Monitoring/Reporting | 3,899 | 85.3% |
| Total | 4,570 | 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 Colorado have the highest number of EPA violations:
| Rank | City | Grade | Violations | Water Systems | Population |
|---|---|---|---|---|---|
| 1 | Denver | C | 207 | 5 | 1,350,703 |
| 2 | Aurora | D | 204 | 5 | 602,310 |
| 3 | Boulder | C | 192 | 5 | 169,750 |
| 4 | Colorado Springs | B | 165 | 5 | 547,861 |
| 5 | Steamboat Springs | C | 150 | 5 | 28,847 |
| 6 | Hotchkiss | C | 92 | 5 | 3,653 |
| 7 | Englewood | C | 91 | 5 | 100,054 |
| 8 | Fort Collins | C | 90 | 5 | 301,072 |
| 9 | Evergreen | D | 90 | 5 | 17,045 |
| 10 | Estes Park | C | 88 | 5 | 21,949 |
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 Colorado:
| Year | Total Violations | Health-Based |
|---|---|---|
| 2021 | 156 | 156 |
| 2022 | 186 | 186 |
| 2023 | 174 | 174 |
| 2024 | 221 | 221 |
| 2025 | 249 | 249 |
| 2026 | 19 | 19 |
Violations have decreased from 156 in 2021 to 19 in 2026, suggesting improving compliance across Colorado.
Most Common Contaminants
The following contaminants have caused the most violations across Colorado water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Lead and Copper Rule | Treatment Technique | 747 | 199 | No |
| E. coli | Microbiological | 531 | 183 | Yes |
| Fecal Coliform | Microbiological | 476 | 196 | Yes |
| Stage 1 DBP Rule | Treatment Technique | 462 | 197 | Yes |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 385 | 179 | Yes |
| Surface Water Treatment Rule | Treatment Technique | 219 | 154 | No |
| Gross Beta | Radionuclides | 218 | 45 | Yes |
| Revised Total Coliform Rule | Microbiological | 209 | 108 | No |
| Total Coliform | Microbiological | 124 | 94 | No |
| Combined Radium | Radionuclides | 98 | 85 | Yes |
How to Check Your Water in Colorado
Enter your ZIP code on ZipCheckup for detailed water system data including contaminant levels, violation history, and safety scores
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 5,733 enforcement actions against water systems in Colorado. 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. Colorado has 671 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 Colorado?
Colorado has 747 community water systems with 4,570 recorded EPA violations, including 671 health-based. Water quality varies by city and ZIP code — check your specific location for detailed results.
How many water violations does Colorado have?
Colorado has 4,570 total EPA violations across 658 ZIP codes. 671 are health-based violations that indicate contaminant levels potentially harmful to human health. The remainder are monitoring or reporting violations.
Which city in Colorado has the worst water quality?
Denver, CO has the most EPA violations among major cities in Colorado with 207 recorded violations. Check individual ZIP codes for the most accurate picture of your local water quality.
Which city in Colorado has the best water quality?
Several cities in Colorado maintain excellent EPA compliance. Check individual city reports for details.
What contaminants are found in Colorado drinking water?
Colorado 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.