Septic rules and requirements in Williamson County, Texas

Septic permits in Williamson County are issued by the county environmental health office. A new system permit costs $510. USDA rates most of the soil in the county Very limited for septic absorption fields — 97.3% of the rated acres. Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23

$510

Septic system permit

checked 2026-09-23

Very limited

USDA rating, 97.3% of rated acres

checked 2026-09-22

Who issues septic permits in Williamson County?

The county environmental health office, at 3151 SE Inner Loop, Ste. B, Georgetown, TX 78626, 512-943-3330. It is part of county government. The state writes the rules it applies.

Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23

What does a septic permit cost in Williamson County?

$510 for a septic system permit, on the county's own schedule.

Applies to a standard septic system permit.

The county's fee table for this permit
Residential Conventional shown above	$510	a home with a conventional system
Residential Non-Conventional / Non-Aerobic	$610	a home with a system the source lists as Non-Conventional / Non-Aerobic
Residential Aerobic Treatment Unit / Routine Maintenance Required	$710	a home with a aerobic system
Commercial Non-Aerobic	$810	a business with a system the source lists as Non-Aerobic
Commercial Aerobic / Routine Maintenance Required	$910	a business with a aerobic system

A non-conventional system costs more, and an aerobic system costs more still. A commercial system costs the most. The state sets no fee here. It lets Williamson County set its own fee.

Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23

How long does approval take in Williamson County?

30 days.

Applies to the first design review.

The department reviews designs in the order it receives them. The state sets this same ceiling for every Texas county.

Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Guide · checked 2026-09-23

Is the soil in Williamson County suitable for a septic system?

USDA rates most of the county Very limited for septic absorption fields — 97.3% of the rated acres. A rating describes the ground, not a parcel. The county's site evaluation decides each lot.

Very limited — 607,473 acres — 97.3% of 624,121 rated acres.
Somewhat limited — 16,648 acres — 2.7% of 624,121 rated acres.
Not rated — 103,400 acres, excluded from the denominator — mostly urban land and water.

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-22

What Williamson County sets itself

The state writes the code. Williamson County adds the rules below. They are what makes this page differ from the Texas requirements.

$510

Applies to a standard septic system permit.

A non-conventional system costs more, and an aerobic system costs more still. A commercial system costs the most. The state sets no fee here. It lets Williamson County set its own fee.

Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23

Sources

Each figure above has a government source and a checked-on date. USDA's Soil Data Access service supplies the soil records. A script writes them, and nobody types them.

Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23
Williamson County, TX — On-Site Sewage Facilities (OSSF) · checked 2026-09-23
Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Guide · checked 2026-09-23
Texas Administrative Code, Title 30, Chapter 285, §285.91(2), Table II · checked 2026-09-23
USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-22

Verify before you act. Septic rules are set locally and they change. Check anything here before you spend money on it. Call the county environmental health office, on 512-943-3330.