Minimum septic tank size by bedrooms
Health departments size the minimum septic tank by number of bedrooms (a proxy for capacity), not by how many people live there today. These are labeled planning bands, not a code citation — your local health department sets the required minimum. Apply them in the tank size and cost by bedrooms tools.
| Bedrooms | Minimum tank (typical) | Design flow @ 75 gpd/person |
|---|---|---|
| 2 | 750 gallons | 300 gpd |
| 3 | 1,000 gallons | 450 gpd |
| 4 | 1,250 gallons | 600 gpd |
| 5 | 1,500 gallons | 750 gpd |
Labeled planning bands — your local health department sets the required minimum tank size (often by bedrooms, sometimes with a garbage-disposal add). Design flow is occupants × gpd/person.