Aerobic Septic System Cost
For poor soils and small lots: $10,000–20,000 installed.
Indicative estimate · not a survey or a design · see methodology
Does the drain field fit? Place tank and field on the plot with the setbacks from the well, the house and the boundary.
Place it on the plotSeptic system cost by type (installed, US 2026)
| System | Installed cost | When it is used |
|---|---|---|
| Conventional | $3,000 – $8,000 | Good soil, enough space for a gravel drain field |
| Chamber | $4,000 – $10,000 | Plastic chambers instead of gravel; easier install |
| Aerobic (ATU) | $10,000 – $20,000 | Poor soil or small lot; needs power and service |
| Mound | $10,000 – $20,000+ | High water table or shallow bedrock |
| Perc test | $250 – $1,000 | Required before design in most counties |
| Drain field alone | $2,000 – $10,000 | Replacement of a failed field |
Source: HomeGuide "Septic Tank System Cost" 2026 ($4,000–12,000 installed; 1,000 gal tank $1,000–1,500); SepticTankHub 2026 (aerobic $10–20k); perc test $250–1,000 (Angi 2026). Tank sizing: common state minimums (1,000 gal up to 3 bedrooms) · verified 2026-08-22
How the estimate is built
tank size from bedrooms (1,000 gal up to 3 bedrooms, 1,250 for 4, 1,500 for 5) · installed range for the system type × tank factor (1,250 gal ≈ 1.1×, 1,500 ≈ 1.2×) + perc test if selected
A 4-bedroom house with a conventional system: 1,250 gal tank → $3,000–8,000 × 1.1 = $3,300–8,800, plus a perc test $250–1,000 → $3,550–9,800.
- Ranges are US 2026 cost-guide figures; coastal and cold-climate states run higher.
- Soil decides the system: a failed perc test forces an aerobic or mound system.
- Tank minimums are set by the county health department; many require 1,000 gal as the floor.
What people use it for
Buying rural land
Order a perc test before closing: if it fails, the septic budget doubles or the lot is unbuildable.
Planning the site
The drain field needs open, unpaved, untravelled ground — often 1,000–2,000 ft² — away from the well.
Adding bedrooms
Health departments size by bedrooms, so an addition may require a bigger tank and field.
Frequently asked questions
How much does a septic system cost?
Typically $4,000 to $12,000 installed for a conventional system, national average about $8,000; aerobic and mound systems $10,000–20,000.
What size septic tank do I need for a 3-bedroom house?
1,000 gallons in most states; 1,250 for 4 bedrooms and 1,500 for 5.
How much does a 1,000 gallon septic tank cost?
About $1,000–1,500 for the tank itself (concrete $800–2,000, plastic $600–1,800); the tank is only 15–30 % of the installed cost.
How much does a perc test cost?
$250 to $1,000, usually a separate line from the installer’s quote.
How big does a drain field need to be?
Depends on soil percolation and bedrooms: often 1,000–2,000 ft² for a family home in average soil.
Why would I need an aerobic or mound system?
Slow-draining soil, a high water table, bedrock or a small lot: the conventional gravel field would not treat the effluent.
Related tools
Sources and author
Terramify editorial team · Research and data verification · Updated August 22, 2026
Source: HomeGuide "Septic Tank System Cost" 2026 ($4,000–12,000 installed; 1,000 gal tank $1,000–1,500); SepticTankHub 2026 (aerobic $10–20k); perc test $250–1,000 (Angi 2026). Tank sizing: common state minimums (1,000 gal up to 3 bedrooms)
Indicative estimate · not a survey or a design · see methodology