waterbycounty
EPA SDWIS

Calvert County Water Quality

Calvert County, Maryland

Water Grade

D

Water Score

50.0

Violations

6

State Rank

#12

of 24 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

D

Based on EPA compliance history and violation data

Water Score

50/100

Higher = better quality

Health Violations

6

Health-based violations

Violation Rate

16.6%

Systems with violations

Water Advisory: Calvert County

Water Verdict

Calvert County receives a below-average water quality assessment with a grade of D and a score of 50.0 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Calvert County has recorded 6 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 16.6 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Residents of Calvert County are advised to use filtered or bottled water for drinking and cooking until water quality improves. A reverse-osmosis or activated-carbon filter certified to remove the contaminants listed in the utility's Consumer Confidence Report is recommended. With 6 recorded health violations, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Calvert County has water quality close to the average county in Maryland. Its water score is within 0.5 points of the state average, meaning its overall water system performance is broadly representative of Maryland as a whole.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

48.9%

23 of 47 assessed

Moderate concern

Top Impairment Causes

  • 1

    TOTAL SUSPENDED SOLIDS (TSS)

  • 2

    FECAL COLIFORM

  • 3

    PHOSPHORUS, TOTAL

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state — counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

73

Active in the past 5 years

Measurements Recorded

46K

45,513 total readings

Most Measured

  • Physical
  • Nutrient
  • Microbiological

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

Improve your water quality at home

Berkey filters remove 99.9%+ of contaminants from tap water.

Shop Berkey →

Sponsored

Test your tap water

Tap Score provides professional mail-in water testing.

Get Tested →

Frequently Asked Questions

What is the water quality in Calvert County, Maryland?
Calvert County, Maryland has a drinking-water quality grade of D with a score of 50.0/100, based on EPA SDWIS compliance data. The county has 6 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Calvert County?
Calvert County has 6 health-based drinking water violations recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.
How healthy are the watersheds in Calvert County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 48.9% of Calvert County's 47 assessed water bodies are classified as impaired (23 impaired). The top reported causes are TOTAL SUSPENDED SOLIDS (TSS), FECAL COLIFORM, PHOSPHORUS, TOTAL. Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in Calvert County?
EPA's Water Quality Portal records 45,513 measurements from 73 monitoring sites in Calvert County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Microbiological. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
How does Calvert County water compare to the Maryland average?
Calvert County's SDWIS water quality score of 50.0/100 is lower than the Maryland state average of 50.5. The average water quality grade across Maryland is D, based on data from 24 counties with available SDWIS data.
Is tap water safe to drink in Calvert County?
Based on EPA SDWIS data, Calvert County has a water quality grade of D (50.0/100). This indicates below-average compliance with significant violations. Residents may want to consider home water filtration or independent testing. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Why does Calvert County have so many water violations?
Calvert County has 6 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.
How does Calvert County rank for water quality in Maryland?
Calvert County ranks #12 out of 24 counties in Maryland by SDWIS water quality score (1 = best). With a score of 50.0/100, it falls in the middle third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Allegany County

Maryland

D

48.6

Water score

Dorchester County

Maryland

D

47.7

Water score

Worcester County

Maryland

D

46.7

Water score

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments — state-reported, EPA-finalized.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP) — federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

By Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

Explore more data for Calvert County

Property TaxCost of LivingCrime RateIncomeHealthSchoolsDisaster RiskWeatherCounty Score