On-site Sewage Facilities (OSSF)

Septic Systems

When city sewer lines are not available to a residence (300 feet with gravity flow), an On-site Sewage Facility (OSSF), also known as a septic system, maybe an alternative. All OSSFs must be compliant with the Texas Administrative Code Ch 285. The Environmental Health Division accepts application, reviews plans for new OSSFs, reviews plans for modifications of existing OSSFs, and conducts inspections as required. If you have any questions or concerns please call City of San Marcos Environmental Health at 512-393-8444.

OSSF Inspection

  • Complaint investigation
  • Connection to city sewer
  • Grey water
  • Inspection
  • Permitting
  • Plan reviews


Licensed Individuals

Only licensed individuals may do site evaluations, designs or installations on an OSSF. To find a current listing of licensed individuals you may visit the TCEQ website. Look under All License Types and select Group Search Criteria.


Septic System Installation

  1. Minimum lots sizes are ½ acre when public water is supplied, 1 acre when a well water is used and 1 acre when the lot is over the Edwards Aquifer Recharge Zone.
  2. Complete application and pay fee. (Checks payable to the City of San Marcos)
  3. Supply site evaluation with application.
  4. Supply septic system design with application - (Type of design determined by Site Evaluation)
  5. Supply copy of house floor plan with application.
  6. File Affidavit with Hays County Clerks Office and supply a copy with application. (This will be determined by the septic system design)
  7. Supply a maintenance contract with application. (This will be determined by the septic system design)