Sump / Ejector Basin Drawdown and Cycle Check
Drawdown volume, run and fill times, cycles per hour.
Example
You enter
- Basin inside diameter (in) 24
- Drawdown band, pump-off to pump-on (in) 12
- Design inflow (GPM) 10
- Pump discharge at system head (GPM) 30
- Minimum acceptable run time (s) 60
You get
- Drawdown volume per cycle 23.5 gal
- Run time per cycle 70.5 s
- Fill time per cycle 141 s
- Cycles per hour 17
Details, formula, and sources
Drawdown volume, run and fill times, cycles per hour, and a short-cycle verdict for a sump or sewage-ejector basin against its inflow and pump rate.
area_ft2 = (PI/4)(basin_dia/12)^2; drawdown_gal = area_ft2 x (drawdown_in/12) x 7.48; run_time_s = drawdown_gal / (pump_gpm - inflow_gpm) x 60; fill_time_s = drawdown_gal / inflow_gpm x 60; cycles_per_hr = 3600 / (run + fill); adequate = run_time_s >= min_run_s.
IPC 2021 Section 712 (Sumps and Ejectors) and the Hydraulic Institute pump-cycling guidance by name; first-principles basin geometry and cycle math.
IPC 2021 free read-only at codes.iccsafe.org; the 7.48 gal/ft^3 constant is public.
Estimate. AHJ and licensed professional govern.
Field names used by the API: basin_dia, drawdown_in, inflow_gpm, pump_gpm, min_run_s, drawdown_gal, run_time_s, fill_time_s, cycles_per_hr
- Volume constant 7.48 gal per ft^3physical fact
- Minimum run default 60 s per cycle (Hydraulic Institute cycling guidance)Hydraulic Institute / pump manufacturer