Updated June 15, 2026
Short answer
In Texas, tank size is set mainly by your home's bedroom count. A 1–3 bedroom home generally needs at least a 750–1,000 gallon tank, a 4-bedroom home around 1,000–1,250 gallons, and larger homes scale up from there. The drainfield is sized separately, by your soil.
Sized by bedrooms
State sizing rules tie minimum tank capacity to bedroom count — a proxy for daily wastewater flow. More bedrooms means a higher design flow and a larger required tank.
Tank vs. drainfield
The tank holds and settles solids; the drainfield disperses the treated liquid into the soil. They're sized differently — the tank by bedrooms, the drainfield by your soil's absorption rate.
Find your size
Our instant estimator returns a recommended tank size and drainfield range from your bedrooms, square footage, and county — in under a minute.
| Bedrooms | Design flow (GPD) | Minimum tank size |
|---|---|---|
| 1–2 | 180 | 750–1,000 gal |
| 3 | 240 | 750–1,000 gal |
| 4 | 300 | 1,000–1,250 gal |
| 5 | 360 | 1,250 gal |
| 6+ | 420+ | 1,250–1,500 gal |
Quick Flow Septic installs new septic systems across Harris County · Montgomery County · Fort Bend County · Waller County · Liberty County.
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