Septic System Cost Calculator
Tank size and installed price for a new septic system.
Updated · How we check our maths
- Estimated installed cost
- $8,800 – $15,300
- Recommended tank size
- 1,000 gallons (minimum; check local code)
- System incl. drain field
- $8,000 – $13,000
- Design, soil test & permit
- $800 – $2,300
- Pumping (every 3–5 years)
- $300 – $600
Quick answer
A new septic system typically costs $8,200–$20,300. Conventional gravity systems run about $8,000–$13,000, aerobic systems $10,000–$20,000 and mound systems $12,000–$20,000, plus $800–$2,300 for design, soil testing and permits. A 3–4 bedroom home usually needs at least a 1,000-gallon tank.
What the Septic System Cost Calculator does
Enter the number of bedrooms and the type of system your soil allows. The calculator suggests a minimum tank size and an installed price range including design and permit costs. Your soil (perc) test decides which system you can use — poor drainage or a high water table usually means a mound or aerobic system.
The formula
Tank: 1 bed 500 gal, 2 beds 750 gal, 3–4 beds 1,000 gal, 5 beds 1,250 gal, 6+ 1,500 gal. Total = system price + design & permits (+ removal if replacing).
Worked example
4-bedroom home, aerobic system: 1,000 gal tank; $10,000–$20,000 + $800–$2,300 = $10,800–$22,300.
How to use the Septic System Cost Calculator
- Enter the number of bedrooms.
- Choose the system type from your soil test or installer's advice.
- Say if you're replacing an old system.
Frequently asked questions
Why is tank size based on bedrooms?
Codes use bedrooms as a proxy for how many people — and how much wastewater — a home can produce.
Why are aerobic systems more expensive?
They add an air pump and treatment unit, and need electricity and annual servicing.
How often should a septic tank be pumped?
Typically every 3–5 years, depending on tank size and household.
Results are estimates for planning and learning. Check important figures with a qualified professional. How we build and check our calculators.