Septic tank size by state / West South Central
Louisiana septic tank size
In Louisiana the minimum septic tank for a three-bedroom house is 1,000 gallons, rising to 1,250 gallons at four bedrooms. The figure comes from LAC 51:XIII.715(D) (Sanitary Code Part XIII, Sewage Disposal), which sizes the tank from design flow; the bedroom figures below are that rule's arithmetic. That matches the 1,000-gallon median of the 47 states listed here.
What the Louisiana rule says
The rule is LAC 51:XIII.715(D) (Sanitary Code Part XIII, Sewage Disposal); design flows in LAC 51:XIII.1501, administered by Louisiana Department of Health, Office of Public Health (State Sanitary Code). In its own words:
§715.D: "The minimum total septic tank liquid capacity required is 2 1/2 times the estimated average daily design flow." … "One-bedroom residences may, however, utilize a 500 gallon tank." NOTE: "The minimum allowable total septic tank volume for all applications is 500 gallons." §1501 table (individual homes): 1 BR 250 gpd; 2 BR 300 gpd; 3 BR 400 gpd; "For each additional bedroom add 100 gpd."
Source: LAC 51:XIII.715(D) (Sanitary Code Part XIII, Sewage Disposal), read 2026-10-20.
- Louisiana sizes the tank at 2.5 times the design daily flow; the bedroom figures here are that arithmetic.
- A one-bedroom home may use a 500-gallon tank.
Louisiana minimum tank size by bedrooms
| Bedrooms | Minimum tank | Versus the median state |
|---|---|---|
| 1 | 500 gal | −500 |
| 2 | 750 gal | — |
| 3 | 1,000 gal | same |
| 4 | 1,250 gal | +50 |
| 5 | 1,500 gal | same |
| 6 | 1,750 gal | — |
The first step up comes at 2 bedrooms, from 500 to 750 gallons, and a six-bedroom house needs 1,750 gallons. Beyond the table the rule adds 250 gallons for each extra bedroom. These are minimums: the permit can call for more, and a bigger tank needs pumping less often.
How Louisiana compares with nearby states
Arkansas requires 1,000 gallons for three bedrooms; Oklahoma requires 1,000 gallons for three bedrooms; Texas requires 1,000 gallons for three bedrooms. 37 of the 47 states listed here share Louisiana's three-bedroom figure.
Before you size a tank in Louisiana
- Bedrooms, not people, set the size in most rules. Rooms that could be used as bedrooms are usually counted, so check how your permitting office counts a den or a finished basement.
- Garbage disposals, grinder or ejector pumps and large tubs change the answer in many states; the points above list Louisiana's adjustments.
- The tank is only half the system. The drainfield is sized separately from soil tests, and it is usually the bigger cost.
- A private well on the same lot has its own setbacks from the tank and field; the well pump and pressure tank calculators size the water side.
Figures are the state's minimum as written on 2026-10-20. Local health departments can require more; the permit issued for your property governs. See the methodology for how each state was read.