ZIP 21771 falls in Frederick County, Maryland, where we hold 6 septic-related documents. We have not classified septic-versus-sewer status for this county, and we do not have a per-ZIP parcel count -- see the county page for what we hold and where the records are kept.
ZCTA 21771 is not entirely inside one county. Land-area share is from the 2020 Census ZCTA-to-county relationship file.
| County | Land in this ZIP | Documents held | On septic (county) | On sewer (county) |
|---|---|---|---|---|
| Frederick County, Maryland | 51% | 6 | — | — |
| Carroll County, Maryland | 26% | — | — | — |
| Howard County, Maryland | 18% | 44,795 | — | — |
| Montgomery County, Maryland | 4% | — | — | — |
2 businesses on record with an address in this ZIP: pumping, installation, design, inspection and repair. Not an endorsement, and we take no fee.
| Company | City | Phone | Rating |
|---|---|---|---|
| JW Boone Septic Inspections | Mount Airy | (240) 656-5706 | 5.0 (1) |
| Wrf & Son Plumbing & Heating Inc | Mount Airy | (301) 831-5280 | 3.0 (10) |
Land-area overlap is from the 2020 Census Bureau ZCTA5-to-county relationship file, not an estimate of ours. Parcel and document counts are rows we hold, not a survey of every property in the ZIP. Last verified 2026-09-01.
We have not measured septic-versus-sewer status for this county yet.
ZIP 21771 spans 4 counties: Frederick County, Maryland, Carroll County, Maryland, Howard County, Maryland, Montgomery County, Maryland.