Septic Drainfield Trench Length
Required absorption area and trench linear feet from design daily flow and the application rate set by your local code.
Example
You enter
- Design daily flow (gpd) 600
- Application rate (gpd / ft²) 0.6
- Trench width (ft) 3
You get
- Required absorption area 1000 ft²
- Trench linear feet 333.3 ft
Checked against published worked examples from: University of Missouri Extension; New York State Department of Health.
Details, formula, and sources
Formula or tableRequired absorption area = design_daily_flow_gpd / application_rate_gpd_per_ft². Trench feet = required_area / trench_width_ft.
Source and editionU.S. EPA Onsite Wastewater Treatment Systems Manual (EPA/625/R-00/008) by name; per-state and per-county application rates set by local code (not bundled).
Free accessFree at epa.gov/septic. State application-rate tables free on each state department of health / DEQ site.
What governsEstimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
API field namesdesign_flow_gpd, application_rate_gpd_per_ft2, trench_width_ft, required_area_ft2, trench_feet
- Application rate user-supplied from local code (this tool deliberately does not bundle a per-state shard)local AHJ