Texas septic rules
Texas septic tank size & cost
Texas doesn't use a bedroom table at all. A typical new 3-bedroom system in Texas runs about $7,600–$12,100 installed by our line-by-line estimate. Below: the state's actual size rule, the full table, and where every number comes from.
Rule: 30 TAC §285.91, Tables II & III · Administered by Texas Commission on Environmental Quality (TCEQ) · Read the official text · Checked 2026-11-10
Texas's rule, in plain words
Texas sizes the tank from your home's wastewater flow, not from a bedroom table. Table III assigns the flow by bedrooms AND living area together; water-saving devices throughout the home qualify for the lower flow column.
Most states print a bedroom-to-gallons table. Texas never did: TCEQ's rule (30 TAC §285.91) first assigns your home a wastewater flow in gallons per day from a table keyed to bedrooms AND living area together (Table III), then converts that flow to a tank size with a second rule (Table II). Two consequences catch people out:
- Water-saving devices genuinely shrink the required tank. A 3-bedroom Texas home flows at 300 gal/day without them and needs a 1,000-gallon tank; with water-saving devices throughout it flows at 240 and needs only 750 gallons.
- Charts that show a flat Texas bedroom table are flattening two tables into one — and quietly dropping the living-area half of Table III.
Table II is not a lookup grid either: past 500 gal/day it switches to formulas — 2.5 × flow up to 1,000 gal/day, then 1,750 + 0.75 × flow. The calculator runs both steps for you, area included.
The Texas size table
Step 1 — your home's wastewater flow (Table III)
| Home (bedrooms, living area) | Flow, no water-saving devices | Flow, with water-saving devices |
|---|---|---|
| 1–2 bedrooms, under 1,500 sq ft | 225 gal/day | 180 gal/day |
| 3 bedrooms, under 2,500 sq ft | 300 gal/day | 240 gal/day |
| 4 bedrooms, under 3,500 sq ft | 375 gal/day | 300 gal/day |
| 5 bedrooms, under 4,500 sq ft | 450 gal/day | 360 gal/day |
| 6 bedrooms, under 5,500 sq ft | 525 gal/day | 420 gal/day |
| Each extra 1,500 sq ft above the row's cap | +75 gal/day | +60 gal/day |
Step 2 — flow to tank size (Table II)
| Wastewater flow Q | Minimum tank |
|---|---|
| Up to 250 gal/day | 750 gal |
| 251–350 gal/day | 1,000 gal |
| 351–500 gal/day | 1,250 gal |
| 501–1,000 gal/day | 2.5 × flow (rounded up to a standard size) |
| Over 1,000 gal/day | 1,750 + 0.75 × flow |
Both tables: 30 TAC §285.91, Tables II & III, read from the official text and re-checked 2026-11-10.
Garbage disposal: Texas Table III flows already assume typical household fixtures; the code adds no separate garbage-disposal allowance.
Permits are issued through TCEQ authorized agents — usually your county or a local designated representative.
Check your Texas home
State minimum — your county can require more. Estimate this system's cost →
What a Texas system costs
Our estimator prices a conventional 3-bedroom system in Texas (typical-cost area, 1,000-gal tank) at $7,600–$12,100 installed, assembled from a soil test, the permit, the tank at published prices, drainfield material, fittings and labor. Build your own estimate →
How Texas compares (3-bedroom minimum)
Full ten-state chart: septic tank size chart.
Other states we've checked
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