How is a septic system sized in Texas?

Texas sizes residential systems by bedrooms and square footage using Table III of 30 TAC Chapter 285. A home with 1 to 2 bedrooms and up to 1,500 sq ft is rated at 180 gallons per day with water-saving fixtures (225 without). Three bedrooms up to 2,500 sq ft is 240 (300 without), 4 bedrooms is 300 (375), and 5 bedrooms is 360 (450). Above 5,500 sq ft, flow increases for each additional 1,500 sq ft. The designer uses that daily flow and the soil's loading rate to size the tank and the drainfield. AgriLife gives the example of a 1,000-gallon tank for a three-bedroom home.

Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.

Sources

• 30 TAC §285.91(3), Table III: Wastewater Usage RateTexas Administrative Code (figure via Justia Regulations)
• Onsite Wastewater Treatment Systems: Septic Tank/Soil Absorption Field (L-5227)Texas A&M AgriLife Extension Service