Septic Systems in Williamson County Start With the OSSF Office

On most rural lots in Williamson County, the waste from your house goes into a septic system rather than a city sewer line, and the county's On-Site Sewage Facilities program is what regulates it. The one big exception is land that falls inside the City of Austin, which is handled separately.

TCEQ authorizes the County Engineer's Office to run the OSSF program, so both the state septic rules and the local county rules apply to the same lot. That stacking matters most on rural acreage, freshly subdivided land, and any property where you're about to change the building footprint.

An old tank in the ground is not a permit for new work. Before you close on land or pour a foundation, line up the application steps, the design requirements, the inspections, and whether the job also triggers a certificate of compliance or a floodplain permit. The OSSF desk would rather walk you through it early than fail a system at inspection.