Codes size on bedrooms. Occupants start to govern the tank at 7 people. Pump every 3.7 years if 3 people live here.
No perc test yet? Loam is the usual soil, in the middle of the scale. The ends are too fast or too slow for a conventional field.
Typical of much of the eastern United States.
1,000 gallon tank and 600 square feet of drainfield, for 360 gallons per day.
Drainfield if the soil is slower
Same house, every perc band. Pick a row to use that soil.
- Design flow
- 360 gal per day
- 3 bedrooms at 120 gal per day each.
- This household
- 180 gal per day
- Assumed 3 people (one per bedroom). Set occupants to refine the pump interval.
- Tank capacity
- 1,000 gal
- Governed by the bedroom table at 3 bedrooms.
- Drainfield area
- 600 sq ft
- 360 gal per day ÷ 0.6 gal per sq ft.
- Soil
- Loam, 16 to 30 min/inch
- 0.6 gal per sq ft per day. Typical of much of the eastern United States.
- Pump the tank
- Every 3.7 years
- Based on a 1,000 gal tank serving 3 people. $450 typical, $250 to $900 per visit.
- Trench layout
- 2 trenches at 100 ft, 3 ft wide
- Three foot trenches are the common default; your installer may use wider beds.
baseline Pick a state to see whether its own code is on file.
Sizing rules are set by your state and enforced by the county. The figures here come from verified state code or the EPA onsite manual baseline.
Pipe and gravel trenches fed by gravity. The cheapest system and the default where soil and slope allow.
Installed cost for this system
$6,150 to $25,400
$15,800 typical. Priced for a 1,000 gal tank with a 600 sq ft field, conventional gravity trench.
See the cost broken down by line item