Also in: Disaster Response and Recovery
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
Checked against published worked examples from: IPC 2021 Section 712 / Hydraulic Institute; ICC (IPC 2021).
Details, formula, and sources
ScopeDrawdown 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.
Formula or tablearea_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; optional sewage discharge check against IPC Table 712.4.2 (2 in 21 gpm, 2-1/2 in 30 gpm, 3 in 46 gpm) with velocity = gpm / (448.83 x (PI/4)(d/12)^2), 448.83 = 60 x 1728/231.
Source and editionIPC 2027 Section 712 (Sumps and Ejectors) and the Hydraulic Institute pump-cycling guidance by name; first-principles basin geometry and cycle math.
Free accessIPC 2027 free read-only at codes.iccsafe.org; the 7.48 gal/ft^3 constant is public.
What governsEstimate. AHJ and licensed professional govern.
API field namesbasin_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
- Ejector minimum capacity 21 / 30 / 46 gpm for a 2 / 2-1/2 / 3 in discharge, each about 2 ft/s in that pipe (added 2026-10-09)IPC 2027 Table 712.4.2 (identical in 2021)