Texas · 30 TAC Chapter 285
Septic system requirements in Texas
Tank sizes, drainfield rules, setbacks, permits, and real costs — pulled from Texas's own code rather than a national average.
- 3-bedroom tank
- 1,000 gal
- Design flow
- 75 gpd/BR
- Typical install
- $6,000–$18,000
- Permit fee
- $250–$900
- Well setback
- 100 ft
- Permitted by
- County / local
Septic tank sizes required in Texas
Texas sizes systems on a design flow of 75 gallons per day per bedroom, with every dwelling rated for at least 2 bedrooms. The tank must meet both the bedroom table below and a 2× daily-flow detention requirement — whichever produces the larger number governs.
| Bedrooms | Design flow | Code minimum | Recommended | With garbage disposal |
|---|---|---|---|---|
| 1 bedroom | 150 gpd | 750 gal | 750 gal | 1,125 gal |
| 2 bedrooms | 150 gpd | 750 gal | 750 gal | 1,125 gal |
| 3 bedrooms | 225 gpd | 1,000 gal | 1,000 gal | 1,500 gal |
| 4 bedrooms | 300 gpd | 1,250 gal | 1,250 gal | 1,875 gal |
| 5 bedrooms | 375 gpd | 1,500 gal | 1,500 gal | 2,250 gal |
| 6 bedrooms | 450 gpd | 1,500 gal | 1,500 gal | 2,250 gal |
Source: 30 TAC Chapter 285. The recommended column rounds the governing requirement up to a tank size manufacturers actually stock.Run your own numbers →
Drainfield size and cost by soil type
For a three-bedroom home in Texas at 225 gpd. This single table explains most of the variation between quotes — the area scales inversely with how fast your soil accepts water, and the drainfield is the largest line item in the job.
| Soil | Loading rate | Absorption area | With reserve | Typical total install |
|---|---|---|---|---|
| Medium sand | 0.8 gpd/ft² | 282 ft² | 564 ft² | $8,100 |
| Sandy loam | 0.5 gpd/ft² | 450 ft² | 900 ft² | $9,400 |
| Loam | 0.4 gpd/ft² | 563 ft² | 1,126 ft² | $10,300 |
| Silt loam | 0.3 gpd/ft² | 750 ft² | 1,500 ft² | $11,800 |
| Clay loam | 0.2 gpd/ft² | 1,125 ft² | 2,250 ft² | $14,800 |
Estimates use Texas's cost index of 0.89× the national average. Build a line-item estimate →
Permits and who issues them
TCEQ writes Chapter 285 and delegates permitting to Authorized Agents — usually the county, sometimes a city or river authority. TCEQ permits directly only where no agent exists.
| Permit required | Yes |
|---|---|
| Typical fee | $250 – $900 |
| Soil evaluation | Required before permit |
| Licensed installer | Required |
| Turnaround | 2–6 weeks |
| Ongoing inspection | Two-year maintenance contract required for aerobic treatment units, renewable thereafter |
| Reserve area | Not specified statewide |
Minimum setback distances
Measured horizontally from the drainfield unless noted. Local rules are frequently stricter, and on a small lot these numbers — not the soil — often decide the layout.
| Private water well | 100 ft |
|---|---|
| Well (septic tank) | 50 ft |
| Property line | 5 ft |
| Surface water | 50 ft |
| Building foundation | 5 ft |
Regulatory contact
Texas Commission on Environmental Quality — On-Site Sewage Facilities
www.tceq.texas.gov · 512-239-3799
What makes septic hard in Texas
Blackland Prairie clay from Dallas through Austin and San Antonio shrinks and swells dramatically. It cracks tanks, shears pipes, and percolates barely at all — which is why aerobic systems dominate that corridor.
Edwards Aquifer recharge and contributing zones carry additional TCEQ requirements and plan review, adding cost and weeks.
Hill Country karst limestone gives thin soil over fractured rock.
Gulf Coast counties combine a high water table with hurricane flooding that floats improperly ballasted tanks.
Things that catch people out
- A garbage disposal increases required tank capacity by 50% in Texas — one of the largest disposal penalties in the country.
- Aerobic units require a maintenance contract for at least the first two years, and most counties require it to continue for the life of the system.
- Your Authorized Agent is usually the county, and their local rules can be stricter than Chapter 285. Always start there, not with TCEQ.
Texas Table III sizes on building area as well as bedroom count, and both Table II and Table III are published only as scanned images. The values shown here reflect the widely-applied Chapter 285 figures, but confirm with your Authorized Agent before ordering a tank.
Texas septic questions
What size septic tank do I need in Texas?
A three-bedroom home in Texas requires a minimum 1,000 gallon tank under 30 TAC Chapter 285. Design flow is 75 gallons per day per bedroom, and the tank must also hold 2 times daily flow, so the practical recommendation is 1,000 gallons.
Do I need a permit for a septic system in Texas?
Yes. TCEQ writes Chapter 285 and delegates permitting to Authorized Agents — usually the county, sometimes a city or river authority. TCEQ permits directly only where no agent exists. Fees typically run $250 to $900, with a turnaround of about 2–6 weeks. A soil evaluation or percolation test is required before a permit is issued.
How much does a septic system cost in Texas?
A conventional system for a three-bedroom home typically runs $6,000 to $18,000 installed. Soil quality moves this more than anything else — on tight clay requiring a mound, budget two to three times the low end.
How far must a Texas drainfield be from a well?
100 feet from a private water well, with the septic tank itself allowed at 50 feet. Local rules can be stricter.
Sources
Every figure on this page traces to one of these documents.
- 30 TAC Chapter 285 — On-Site Sewage Facilities · verified 2026-09-18
- 30 TAC §285.32 — Criteria for Sewage Treatment Systems · verified 2026-09-18
- 30 TAC §285.91 — Tables (II, III, X) · verified 2026-09-18