A new septic system costs about $3,615 to $12,408 to install, with a national average of $8,011, according to Angi. A conventional gravity system runs about $3,000 to $8,000, while engineered systems such as mound or aerobic systems cost $10,000 to $20,000. Budget $700 to $2,000 for the perc test and $450 to $2,300 for permits.
How much does each type of septic system cost?
| System type | Typical installed cost |
|---|---|
| Conventional (anaerobic, gravity) | $3,000–$8,000 |
| Chamber | $5,000–$12,000 |
| Constructed wetland | $5,000–$12,000 |
| Sand filter | $7,000–$18,000 |
| Drip distribution | $8,000–$18,000 |
| Evapotranspiration | $10,000–$15,000 |
| Mound | $10,000–$20,000 |
| Aerobic treatment unit | $10,000–$20,000 |
The soil decides the system. Good, well-draining soil allows a conventional system; poor drainage, a high water table or shallow bedrock usually means an engineered system such as a mound or aerobic unit.
How much does a septic tank cost by house size?
| Bedrooms | Tank size | Tank cost |
|---|---|---|
| 1 | 500 gallons | $500–$900 |
| 2 | 750 gallons | $700–$1,200 |
| 3–4 | 1,000 gallons | $900–$1,500 |
| 5–6 | 1,200 gallons | $1,200–$1,600 |
| 6–7 | 1,500 gallons | $1,500–$2,500 |
Local health codes set the minimum tank size, usually by number of bedrooms.
Other septic costs
- Perc (percolation) test: $700–$2,000
- Permits: $450–$2,300
- Drain field (leach field): $5,000–$12,000 if priced separately
- Excavation: $1,500–$6,300 if not included
When do you need a septic system?
If your lot cannot connect to a public sewer, you need an on-site system. Have a perc test done before you buy rural land: a failed test can make a lot unbuildable or force an expensive engineered system. See land cost and well drilling cost.
Frequently asked questions
How long does a septic system last?
With regular pumping and care, many systems last decades, but drain fields can fail sooner in poor soil.
Is septic cheaper than sewer?
The install can cost more than a sewer tap, but there is no monthly sewer bill. Sewer connection fees vary widely by town.
More cost breakdowns
- Full cost breakdown by stage
- Foundation cost
- Framing cost
- Roofing cost
- Electrical wiring cost
- Material cost
- Land cost
- Septic system cost
- Well drilling cost
- Driveway cost
- House plans cost
Sources
- Angi: How much does a septic system cost? (2025 data)