Maryland Water Quality Report: 1,178 Water-System Violations Mapped to 359 ZIPs
538 water systems · 359 ZIP codes · 1,178 violations
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO
ZipCheckup tracks EPA drinking-water compliance for 538 public water systems serving 359 ZIP codes in Maryland. The state record shows 1,178 EPA violations, 203 health-based.
City Water Quality Map: Maryland
Each circle represents a city. Size indicates population, color indicates water quality grade. Tap a circle for details.
Cities with Most Violations in Maryland
| # | City | Grade | Violations | Systems | Population | |
|---|---|---|---|---|---|---|
| 1 | Perryville | 54 | 5 | 5,679 | Details → | |
| 2 | Perry Point | 39 | 2 | 313 | Details → | |
| 3 | Baltimore | 22 | 4 | 593,135 | Details → | |
| 4 | Havre De Grace | 22 | 4 | 20,002 | Details → | |
| 5 | Elkton | 19 | 5 | 45,698 | Details → | |
| 6 | Lexington Park | 19 | 5 | 26,799 | Details → | |
| 7 | Halethorpe | 18 | 2 | 35,695 | Details → | |
| 8 | Rockville | 16 | 2 | 144,320 | Details → | |
| 9 | Potomac | 16 | 2 | 49,694 | Details → | |
| 10 | North East | 16 | 5 | 19,585 | Details → |
Most Common Contaminants in Maryland
| Contaminant | Category | Violations | ZIPs Affected | Health Risk |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | Treatment Technique | 189 | 126 | Yes |
| Lead and Copper Rule | Treatment Technique | 167 | 91 | No |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 165 | 111 | Yes |
| Nitrate | Inorganic | 162 | 129 | No |
| Toxaphene | Organic | 154 | 81 | No |
| Chlordane | Organic | 132 | 70 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 78 | 51 | Yes |
| Public Notice Rule | Reporting | 64 | 64 | No |
| Consumer Confidence Rule | Reporting | 53 | 36 | No |
| Fluoride | Inorganic | 35 | 21 | No |
Water Quality Overview
Maryland has 538 community water systems represented across 359 directly mapped ZIP records. The associated city records cover approximately 6,042,905 people. The available records contain 1,178 EPA violations, including 203 health-based violations.
Health-based violations account for 17% of all violations in Maryland. 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 | 203 | 17.2% |
| Monitoring/Reporting | 975 | 82.8% |
| Total | 1,178 | 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 Maryland have the highest number of EPA violations:
| Rank | City | Violations | Water Systems | Population |
|---|---|---|---|---|
| 1 | Perryville | 54 | 5 | 5,679 |
| 2 | Perry Point | 39 | 2 | 313 |
| 3 | Baltimore | 22 | 4 | 593,135 |
| 4 | Havre De Grace | 22 | 4 | 20,002 |
| 5 | Elkton | 19 | 5 | 45,698 |
| 6 | Lexington Park | 19 | 5 | 26,799 |
| 7 | Halethorpe | 18 | 2 | 35,695 |
| 8 | Rockville | 16 | 2 | 144,320 |
| 9 | Potomac | 16 | 2 | 49,694 |
| 10 | North East | 16 | 5 | 19,585 |
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 Maryland:
| Year | Health-based violations |
|---|---|
| 2021 | 7 |
| 2022 | 71 |
| 2023 | 12 |
| 2024 | 54 |
| 2025 | 32 |
| 2026 | 66 |
Health-based violations have increased from 7 in 2021 to 66 in 2026. 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 Maryland water systems:
| Contaminant | Category | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|
| Lead and Copper Rule Revisions | Treatment Technique | 189 | 126 | Yes |
| Lead and Copper Rule | Treatment Technique | 167 | 91 | No |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 165 | 111 | Yes |
| Nitrate | Inorganic | 162 | 129 | No |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 78 | 51 | Yes |
| Public Notice Rule | Reporting | 64 | 64 | No |
| Consumer Confidence Rule | Reporting | 53 | 36 | No |
| Fluoride | Inorganic | 35 | 21 | No |
| Total organic carbon | Disinfection Byproducts | 14 | 9 | Yes |
| Interim Enhanced Surface Water Treatment Rule | Treatment Technique | 13 | 9 | Yes |
How to Check Your Water in Maryland
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 Maryland. 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. Maryland has 203 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 Maryland?
Records for 538 community water systems mapped to ZIPs in Maryland show 1,178 reported violations, including 203 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 Maryland?
Maryland has 1,178 EPA violations on record across 359 ZIP codes; 203 are classified as health-based violations. The remainder are monitoring or reporting violations.
Which city in Maryland has the worst water quality?
Perryville, MD has the most recorded EPA violations (54) among the cities with mapped water systems in Maryland 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 Maryland has the best water quality?
Violation records vary by water system across Maryland. Check individual city reports for details.
What contaminants are found in Maryland drinking water?
EPA regulates over 90 drinking-water contaminants nationally; water systems in Maryland 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.