Calculation sequence
Step-by-step method
- Apply the visible approved peaking factor to base inflow.
- Add static, friction, and residual head components.
- Review the point against the full system curve and manufacturer data.
PlumbingAdvancedSanitary Drainage Pumps
Sewage-Ejector Pump Duty Calculator
Assemble a preliminary sewage-ejector flow and head duty point from visible user-approved inputs.
Why it matters: Peaking, static lift, system loss, and discharge condition must be explicit before equipment review.
Calculated result
Engineering evaluation
Required sewage-ejector flow (Qᵖ)125 gpm
- Preliminary total dynamic head (TDH)
- 40 ft
Engineering interpretation
The entered basis yields preliminary duty 125 gpm at 40 ft TDH.
Important limitations
- Sewage/ejector screening only. Do not select equipment from this result alone. Confirm biological, exposure, confined-space and electrical hazards; solids handling; pump/system curves; basin/cycling; duplex redundancy; valves; emergency storage; alarms; receiving pressure; and code criteria.
Motor-driven equipment
Estimate electrical demand and energy use
Use nameplate information and an operating schedule to screen motor input power, current, annual energy, and operating cost. Results update automatically.
Choose the motor nameplate output-power convention.
Rated shaft output, not electrical input.
Used to estimate current; it does not change the hp-based energy result.
Use efficiency at the evaluated load point when available.
Use measured or defensible operating load rather than motor nameplate size alone.
Used only for the estimated current calculation.
Assumes all selected motors operate concurrently at the entered load.
Replace the profile with the actual occupied, process, or control schedule.
$/kWh
Use the applicable marginal utility energy charge; demand charges are not included.Estimated result
Total motor input power (Pin,total)6.21 kW
- Current per motor (I)
- 9.18 A
- Total coincident current (Itotal)
- 9.18 A
- Daily energy (Ed)
- 50 kWh/day
- Annual operating hours (Hy)
- 2,080 h/year
- Annual energy (Ey)
- 12,925 kWh/year
- Annual energy cost (Cy)
- $1,551/year
Equations and assumptions
Nameplate-based screening method
Horsepower is converted using 1 hp = 0.7457 kW. This estimate assumes steady average load and the entered operating-point efficiency. Voltage and power factor affect estimated current, but hp, load, efficiency, quantity, and schedule establish the energy estimate. VFD speed profiles, cycling, standby power, demand charges, and process variation require separate evaluation.
Technical basis: U.S. Department of Energy — Determining Electric Motor Load and EfficiencyEngineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Qᵖ=Fᵖ·Qᵢ
TDH=Hˢ+Hᶠ+Hʳ
Current substitution
Qᵖ=1.25×100=125; TDH=20+15+5=40.
Equation legend
Inputs and calculated quantities
- Qᵢ
- Base design inflow — gpm or L/s
- Fᵖ
- Approved peaking factor — ratio
- Hˢ
- Static lift — ft or m
- Hᶠ
- Piping and fitting loss — ft or m
- Hʳ
- Required discharge residual head — ft or m
- Qᵖ
- Required sewage-ejector flow — gpm
- TDH
- Preliminary total dynamic head — ft
Applications
How this calculation is used
Building design
Screen a preliminary ejector duty point.
Construction
Check head and inflow components against approved documents.
Commissioning
Compare a field operating point with the stated duty basis.
Quality controls
Assumptions and limitations
Assumptions
- Entered values describe one documented system and use a consistent unit, energy, pressure, elevation, and measurement basis.
- Measurements are representative and synchronized where the calculation combines field readings.
Limitations
- This tool does not select a pump, basin, solids passage, redundancy arrangement, controls, alarms, valves, or emergency storage.
- Sewage exposure, confined-space, electrical, biological, code, inflow, cycle, pump-curve, and receiving-system hazards require approved procedures and professional/manufacturer review.
Field use
Verification procedure
- Confirm the calculation boundary, source documents, formula symbols, and units.
- Record representative field values or approved project inputs and their sources.
- Review the result against the applicable code, criteria, manufacturer data, and measurement uncertainty.
Common engineering mistakes
- Combining values from different system boundaries, operating periods, temperature bases, or unit conventions.
- Treating a calculated screening value as a hidden pass/fail threshold or final design decision.
Technical basis
References and source standards
- International Plumbing Code, 2024The legally adopted edition and local amendments govern water, sanitary, storm, sump, and pumping requirements; protected code tables are not reproduced.
- Hydraulic InstitutePump-system, test-boundary, and manufacturer-curve context; exact equipment data remain controlling.
- NIST SI and Unit Conversion GuidanceUnit symbols, pressure, flow, energy, temperature, and dimensional conversions used by the application.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement