Size your commercial septic system based on building type and occupancy. Get tank capacity, drainfield area, and cost estimates for planning and budgeting.
Default for Restaurant: 35 gal
From perc test. Typical: 10-60
Daily Design Flow
2,800 GPD
80 seats x 35 gal/day
Tank Size
6,000 gal
Single tank
Drainfield Area
5,600 sq ft
19 trenches, 1,867 ft total
Soil Classification
Moderate (loam)
Application rate: 0.5 gal/sqft/day
Estimated Total Cost
$64K - $106K
Mid estimate: $85K
| Component | Estimated Cost | % of Total |
|---|---|---|
| Septic Tank — 6,000 gal | $12,000 | 14% |
| Drainfield — 5,600 sq ft | $44,800 | 53% |
| Excavation & Grading | $18,800 | 22% |
| Engineering & Design | $8,000 | 9% |
| Permits & Inspections | $1,500 | 2% |
| Total Estimated Cost | $85,100 | 100% |
Costs are rough estimates. Actual costs vary by region, soil conditions, and local code requirements. Budget range: $64K - $106K.
Need a commercial septic system?
Get quotes from licensed commercial septic installers.
No obligation. Free. Takes 30 seconds.
Commercial septic systems must handle significantly higher flows than residential systems. Design flows are based on building type and occupancy, with safety factors of 1.5-2x applied to the peak daily flow.
| Building Type | Unit | Gallons/Day per Unit |
|---|---|---|
| Restaurant | Per seat | 35-50 |
| Hotel/Motel | Per room | 75-100 |
| Office Building | Per employee | 15-25 |
| Church | Per seat | 3-7 |
| School (no showers) | Per student | 12-18 |
Commercial systems range from $20,000 to $150,000+ depending on daily flow volume, soil conditions, and system complexity. Advanced treatment systems (required in many jurisdictions for restaurants and high-flow facilities) add 30-50% to conventional system costs.