St. Marys County Water Quality: 40 Violations (MD)
22 water systems · 14 ZIP codes · Average ZIP-level Home Safety model score Unavailable · 0 of 28 tracked ZIP records scored
Data: EPA Safe Drinking Water Information System (SDWIS), EPA ECHO
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Find the Right Filter →Water Quality Overview
St. Mary's County has 22 community water systems across 14 directly mapped ZIP records. The systems report serving approximately 84,506 people. The available records contain 40 EPA violations, including 3 health-based violations.
Health-based violations account for 8% of all violations in St. Mary's County. These violations indicate contaminant levels that may pose direct risks to human health.
Year-by-year violation counts, enforcement actions and violation counts by contaminant are not shown for this county: the source records them per ZIP code, so a water system serving several ZIP codes would be counted several times. The county totals above count each water system once.
Violation Breakdown
| Violation Type | Count | Percentage |
|---|---|---|
| Health-based | 3 | 7.5% |
| Monitoring/Reporting | 37 | 92.5% |
| Total | 40 | 100% |
Health-based violations are MCL, MRDL (disinfectant) and treatment-technique violations. Monitoring violations indicate failures to test or report.
Cities with Most Violations
| Rank | City | Violations | Health-Based | ZIP Codes | Population |
|---|---|---|---|---|---|
| 1 | Lexington Park | 19 | 3 | 1 | 26,799 |
| 2 | Leonardtown | 13 | 0 | 1 | 15,979 |
| 3 | California | 12 | 1 | 1 | 14,743 |
| 4 | Mechanicsville | 11 | 0 | 1 | 23,918 |
| 5 | Hollywood | 11 | 0 | 1 | 10,357 |
| 6 | Great Mills | 9 | 1 | 1 | 6,976 |
| 7 | Patuxent River | 7 | 0 | 1 | 1,577 |
| 8 | Park Hall | 5 | 0 | 1 | 98 |
| 9 | Chaptico | 4 | 0 | 1 | 902 |
| 10 | Clements | 3 | 0 | 1 | 1,157 |
Most Common Contaminants
| Contaminant | Category | ZIPs Affected | Health-Based |
|---|---|---|---|
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 14 | No |
| Nitrate | Inorganic | 8 | No |
| Lead and Copper Rule Revisions | Treatment Technique | 7 | Yes |
| Haloacetic Acids (HAA5) | Disinfection Byproducts | 9 | No |
| Lead and Copper Rule | Treatment Technique | 4 | No |
| Fluoride | Inorganic | 1 | No |
| Consumer Confidence Rule | Reporting | 1 | No |
Water Data and the Home Safety Score
This page reports EPA water-system facts without converting the broader Home Safety Score into a drinking-water grade. The county Home Safety grade (unavailable) is a separate multi-source index that also requires PFAS screening, radon, and annual air-quality evidence. Check each ZIP report for the versioned score and its component coverage.
Water Systems in St. Mary's County
St. Mary's County is served by 22 community water systems, averaging 0.8 systems per ZIP code. Each system is independently regulated and tested by the EPA. Larger systems serving more people typically have more extensive monitoring requirements.
Water systems in St. Mary's County source water from a mix of surface water (rivers, reservoirs) and groundwater (wells, aquifers). Source type affects which contaminants are most likely to be detected.
How to Check Your Water in St. Mary's County
Enter your ZIP code on ZipCheckup for detailed water-system data including contaminant levels and violation history; the Home Safety Score is shown separately with its model version
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) can detect contaminants not covered by routine testing
Consider filtration — NSF-certified filters can address specific contaminants found in your area
Check for lead — homes built before 1986 should test for lead regardless of utility compliance
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Enforcement: EPA ECHO
Source publication schedules vary. See the page source and verification fields for available timing evidence.
Water Quality by ZIP Code in St. Mary's County
Water quality varies across St. Mary's County's 14 ZIP codes. Each row counts the EPA violations of every water system mapped to that ZIP, so a system serving several ZIP codes appears in several rows and the rows do not add up to the county total. Check your specific ZIP for detailed contaminant data.
| ZIP Code | City | Violations | Health | |
|---|---|---|---|---|
| 20653 | Lexington Park | 19 | 3 | View → |
| 20650 | Leonardtown | 13 | 0 | View → |
| 20619 | California | 12 | 1 | View → |
| 20636 | Hollywood | 11 | 0 | View → |
| 20659 | Mechanicsville | 11 | 0 | View → |
| 20634 | Great Mills | 9 | 1 | View → |
| 20670 | Patuxent River | 7 | 0 | View → |
| 20667 | Park Hall | 5 | 0 | View → |
| 20621 | Chaptico | 4 | 0 | View → |
| 20624 | Clements | 3 | 0 | View → |
| 20656 | Loveville | 2 | 0 | View → |
| 20692 | Valley Lee | 2 | 0 | View → |
| 20620 | Callaway | 1 | 0 | View → |
| 20630 | Drayden | 1 | 0 | View → |
Water facts and the Home Safety Score
This page reports water evidence separately. A broader Home Safety Score is not published here unless the versioned model identity and complete required component coverage are available.
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Find the Right Filter →Frequently Asked Questions
Is the tap water safe in St. Mary's County, Maryland?
St. Mary's County has 22 community water systems with 40 recorded EPA violations, including 3 health-based. Water quality varies by ZIP code - check your specific location for detailed results.
How many water violations does St. Mary's County have?
The 22 water systems with EPA records that serve ZIP codes in St. Mary's County have 40 recorded EPA violations, each system counted once. 3 are health-based.
Which city in St. Mary's County has the most water violations?
Lexington Park has the most violations in St. Mary's County with 19 recorded EPA violations for the 8 water systems serving its 1 ZIP code.
What contaminants are found in St. Mary's County water?
St. Mary's County water systems are monitored for over 90 EPA-regulated contaminants including lead, copper, nitrates, disinfection byproducts, and bacteria. Check your ZIP code for contaminant-specific data.
How can I test my water in St. Mary's County?
Contact your local water utility for free or low-cost testing. You can also use a certified home test kit ($20-$50) or hire a certified lab ($150-$400).