ZIP 78642 falls in Williamson County, Texas, where we hold 110,116 parcels measured as septic county-wide and 176,652 on sewer. We do not have a per-ZIP parcel count for this county, so this is the county total, not a count specific to ZIP 78642.
ZCTA 78642 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) |
|---|---|---|---|---|
| Williamson County, Texas | 92% | — | 110,116 | 176,652 |
| Burnet County, Texas | 8% | — | — | — |
1 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 |
|---|---|---|---|
| MPH Septic Design | Liberty Hill | (512) 710-9919 | — |
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 hold 110,116 parcels measured as septic for Williamson County, Texas as a whole, not broken out by ZIP.
ZIP 78642 spans 2 counties: Williamson County, Texas, Burnet County, Texas.