We have 3,626 parcels measured as septic in ZIP 77521 itself (Harris County, Texas), out of 20,676 parcels in our records for this ZIP, of which 17,050 are recorded as on sewer.
ZCTA 77521 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) |
|---|---|---|---|---|
| Harris County, Texas | 77% | — | 128,872 | 1,412,534 |
| Chambers County, Texas | 23% | — | — | — |
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 measured 3,626 parcels as septic in ZIP 77521 itself, out of 20,676 parcels in our records for this ZIP.
ZIP 77521 spans 2 counties: Harris County, Texas, Chambers County, Texas.