Septic tank size chart
| Bedrooms | Typical minimum tank |
|---|---|
| 2 | 750 gallons |
| 3 | 1,000 gallons |
| 4 | 1,250 gallons |
| 5 | 1,500 gallons |
| 6 or more | 1,750 gallons |
Codes differ by state. Many set 1,000 gallons as the smallest tank allowed for any new home. The drain field is sized separately from your soil test and daily flow. To see how size affects maintenance, try the pumping frequency calculator, or read how a septic tank works.
Common questions
What size septic tank do I need for a 3-bedroom house?
A 1,000-gallon tank is the most common minimum for a three-bedroom home in US codes. Some states require more, so check with your county health department.
Why is septic tank size based on bedrooms?
Bedrooms predict how many people a house can hold over its life, so codes use them to estimate daily wastewater flow. The number of people living there today does not change the required size.
Does a garbage disposal need a bigger tank?
Often yes. Food waste adds solids that fill the tank faster, and some states require extra capacity or more frequent pumping when a disposal is installed.
Is a bigger septic tank better?
A larger tank holds more sludge between pump-outs and gives solids more time to settle, which protects the drain field. It costs more up front, and the drain field still has to be sized for your daily flow.
Sources
- HomeGuide: How much does a septic system cost?
- HomeGuide: Engineered septic system cost
- HomeGuide: Drain or leach field replacement cost
- HomeGuide: How much does septic tank pumping cost?
- HomeGuide: Septic inspection cost
- This Old House: How much does a septic tank installation cost?
- This Old House: How much does it cost to pump a septic tank?
- Bob Vila: How much does a septic tank cost?
- Bob Vila: How much does it cost to replace a septic tank and drain field?
- Fixr: How much does it cost to install a septic tank system?
- HomeAdvisor: Sewer line installation cost (septic tank abandonment)