Septic permits and fees in Williamson County, Texas
A septic system permit in Williamson County costs $510. The county sets that fee in its own schedule. State rules fix the tank floor at 1,000 gallons. A private well needs 100 feet from the drainfield, a property line 5 feet. Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23
$510
Septic system permit
checked 2026-09-23
1,000 gallons
Tank floor, state rule
checked 2026-09-23
100 feet
Drainfield to a well
checked 2026-09-23
Which septic permit applies in Williamson County?
The septic system permit, and it starts with the site evaluation. Williamson County requires a site evaluation, not a percolation test, before a permit. A licensed evaluator or an engineer must perform it. The permit follows a passing evaluation. The building permit follows the septic permit.
The state sets this same requirement for every Texas county. Williamson County's own guide restates it in full.
Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Guide · checked 2026-09-23
What are the current septic fees in Williamson County?
$510 for a septic system permit, on the county's own fee schedule.
Applies to a standard septic system permit.
| Residential Conventional | $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 a septic permit 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
What state law fixes for every Texas system
-
1,000 gallons minimum septic tank capacity
Applies to a 3-bedroom house.
A 1- or 2-bedroom house can use the smaller floor instead.
Texas Administrative Code, Title 30, Chapter 285, §285.91(2), Table II · checked 2026-09-23
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100 feet from a private well to the drainfield
Applies to a private well or cistern, measured to the drainfield.
The same table sets a shorter 50-foot distance from the well to the tank itself. Williamson County's own guide states this same 100-foot figure.
Texas Administrative Code, Title 30, Chapter 285, §285.91(10), Table X · checked 2026-09-23
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5 feet from any property line
Applies to a tank or a drainfield, measured from a property line, a building, or a pool.
A spray system uses a different distance. The county's own guide states the same figure.
Texas Administrative Code, Title 30, Chapter 285, §285.91(10), Table X · checked 2026-09-23
Where do you file the application with the county environmental health office?
The county environmental health office, 3151 SE Inner Loop, Ste. B, Georgetown, TX 78626, 512-943-3330.
Williamson County, TX — On-Site Sewage Facilities (OSSF) · checked 2026-09-23
The steps, in the county's order
- Apply online through MyGovernment Online.
- A licensed evaluator or an engineer checks the site and the soil.
- An engineer or a sanitarian must design the system. Send the design for review.
- Wait for the department's written Authorization to Construct.
- Build the system. Schedule the county's inspections.
- Get the permit to operate. All inspections must pass first.
Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Guide · checked 2026-09-23
How do you get a copy of your septic permit record in Williamson County?
Ask the county environmental health office for the permit record for the property. Call 512-943-3330 or start at its website.
Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees · checked 2026-09-23
Sources
Each figure on this page has a government source and a checked-on date.
- Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Program Fees
- Williamson County, TX — On-Site Sewage Facilities (OSSF)
- Williamson County Department of Infrastructure — On-Site Sewage Facility (OSSF) Guide
- Texas Administrative Code, Title 30, Chapter 285, §285.91(2), Table II
- USDA NRCS Soil Data Access (SSURGO)
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.