Water quality · Maryland
Water quality in Maryland
2 of the 3 Maryland ZIPs matched to an EPA SDWIS community water system report a health-based violation in the last 3 years. 2 further ZIPs have no water-system record on zipradar yet. That is a gap in our records, not a sign that the water is untested. SDWIS reports the system serving the county, never an address-level test, and never private wells.
Last verified 2026-09-24 · methodology
Water quality by ZIP code in Maryland
The largest community water system EPA lists for each ZIP's county, and its health-based violations in the last 3 years.
| ZIP | Largest system | Health-based violations |
|---|---|---|
| 21201BaltimoreBaltimore (city) | CITY OF BALTIMORE | 1 |
| 20850RockvilleMontgomery County | No record yet | |
| 21401AnnapolisAnne Arundel County | CITY OF ANNAPOLIS | None |
| 21202BaltimoreBaltimore City | CITY OF BALTIMORE | 1 |
| 20815Chevy ChaseMontgomery County | No record yet |
County-level figures from EPA SDWIS, joined to each ZIP by county. None of them is a measurement at a specific address.
What lands here
Pages show the largest community water system on record for the ZIP's county, its PWSID and population served, and its health-based and total violations in the last 3 years. Lead and copper sampling results are not shown; your utility's annual water quality report (CCR) has them.
Source & refresh
EPA SDWIS. Refreshed quarterly (federal mandate). Primary source →
Maryland top concern
Chesapeake flood, lead pipes
Maryland has dense FEMA NFHL coverage along Chesapeake Bay tributaries. Baltimore City has extensive LCRR lead-service-line obligations and flagged EPA SDWIS compliance history. Radon Zone 1-2 across most counties.
See Maryland state page for the full state-level rollup across all 12 dimensions.
Read more on water quality
Editorial deep-dives explaining the source data, its limits, and how to read it.
Flood zones explained — what AE, X, and VE actually mean
Plain-English guide to FEMA flood-zone codes (A, AE, AH, V, VE, X, X-shaded). What the 1% and 0.2% annual-chance zones mean for your property and your insurance.
EPA Radon Zones — what 1, 2, and 3 mean and when you should test
EPA classifies every US county into Zone 1 (high), Zone 2 (moderate), or Zone 3 (low) for radon. Plain-English guide to the classifications and at-home testing.
EPA AQI categories explained — what 0–50 Good through 301–500 Hazardous mean
Plain-English guide to the six EPA Air Quality Index categories: 0–50 Good, 51–100 Moderate, 101–150 Unhealthy for Sensitive Groups, 151–200 Unhealthy, 201–300 Very Unhealthy, 301–500 Hazardous — what each level means and who is at risk.
Lead and Copper Rule 2024 — the federal lead-pipe inventory mandate
The 2024 Lead and Copper Rule Revisions (LCRR) require every US community water system to inventory and report lead service lines. Plain-English guide.