Official sources checked August 29, 2026

Hays County, Texas septic permits and requirements

Texas permitting framework

Texas requires applicants to work with the local permitting authority where an authorized local OSSF program exists. TCEQ notes that local programs can be more stringent than statewide minimums, so county-specific procedures control within the county program’s jurisdiction.

Permit required regardless of lot size

Hays County states that a permit is required for every OSSF regardless of the acreage or lot size on which it is installed. Newly constructed systems, replacement systems, and alterations to existing systems all require permits.

Unincorporated-area county program

Hays County Environmental Health administers development and OSSF permitting in the unincorporated areas of the county. Applicants use the county online permitting system and should verify jurisdiction if the property is inside a municipality.

Design documents and technical review

The county application calls for the OSSF application, site plan and design, location map, floor plan, tax-account information, and applicable fees. After administrative review, an inspector conducts technical review and may issue the Authorization to Construct, followed by the Notice of Approval when requirements are satisfied.

Licensed designer determines system type and size

Hays County states that the septic-system type and size are determined by the licensed septic designer. Additions or newly created conditioned square footage can require a development permit and may require an OSSF upgrade because permitted capacity is tied to the structure served.

Advanced and aerobic systems require ongoing maintenance

The county requires ongoing maintenance for all aerobic or advanced-treatment OSSFs. Its application materials also require a maintenance affidavit and an initial two-year maintenance contract for advanced/aerobic systems.

Official sources

• Texas Commission on Environmental Quality — Getting a Permit for an OSSF
• Texas Commission on Environmental Quality — OSSF Licensing
• Hays County — Septic Permits
• Hays County — On-Site Sewage Facilities
• Hays County — Development Services FAQ

SepticScope summarizes public-agency information for planning purposes. The permitting agency's current instructions control if they differ from this guide.