Lift Station Runtime & Backup Power Calculator Skip to main content
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Lift Station Runtime & Backup Power Calculator - Pump Cycles, Backup Power & Overflow Time

Size generators and calculate time to overflow for any lift station

Check pump cycles per day, lead pump runtime, backup-power load, local generator kW calculator, fuel runtime, and wet-well overflow time for wastewater lift-station planning. Enter daily flow, active wet-well volume, pump rate, motor HP, fuel tank size, and auxiliary load to see the simple arithmetic and the source gaps that must be reconciled before design, equipment, safety, or compliance use.

Pro Tip: Overflow time is a storage calculator, not a spill prediction. Treat a short time as a reason to verify current wet-well level, alarms, response time, bypass pumping, upstream storage, generator status, fuel logistics, and reporting requirements with the local operating plan and reviewing authority.

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Lift Station Runtime & Backup Power Calculator
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How It Works

  1. Enter Station Configuration

    Input average daily flow (GPD), wet well active volume (gallons between lead-on and lead-off levels), pump flow rate (GPM), and number of pumps.

  2. Enter Pump and Motor Data

    Input pump HP for the local load calculator. Then verify motor nameplate, starting method, pump curve, and actual TDH separately.

  3. Configure Backup Power

    Enter fuel tank size, auxiliary load, motor efficiency, and either a manual generator rating or the local auto-screen option.

  4. Review Overflow and Source Gaps

    Compare average and peak overflow time, then reconcile alarms, response, bypass pumping, fuel logistics, permit, and qualified-review requirements.

Built For

  • Collection system operators screening outage storage and alarm-response assumptions
  • Public works teams comparing local backup-power load and fuel-runtime inputs before supplier review
  • Engineers preparing preliminary lift-station planning checks before full hydraulic and electrical design
  • Emergency planners reconciling response-time, bypass-pumping, and reporting assumptions
  • Operators tracking pump cycles as a maintenance and investigation flag

Assumptions

  • Average daily flow is assumed constant and evenly distributed over 24 hours for baseline pump cycle calculations
  • Wet well active volume is the usable volume between lead-on and lead-off level setpoints
  • Pump capacity is at the rated duty point and does not account for impeller wear, clogging, or system curve shifts
  • Generator load screen uses a local 6x starting multiplier and a 1.25 running-load comparison
  • Fuel consumption auto-estimate uses a local 0.07 gallons per hour per effective generator kW diesel calculator
  • Overflow time is calculated from entered active wet-well volume only, not rim elevation, invert elevation, or upstream storage

Limitations

  • Does not model inflow and infiltration (I/I), diurnal peaks, upstream storage, or current wet-well level at outage start
  • Pump cycling calculations assume constant inflow and simple on/off control
  • Generator load analysis is simplified and does not account for soft starters, VFDs, reduced-voltage starting methods, voltage dip, ATS sequence, or generator transient capability
  • Does not evaluate force main hydraulics (friction loss, air release, surge protection) that affect actual pump discharge rate
  • Overflow screen does not account for emergency bypass pumping, tanker response, alarms, notification cascade, or spill reporting rules
  • Does not calculate SCADA alarm setpoints, telemetry requirements, NEC/AHJ requirements, NFPA 110 classification, or fuel-quality maintenance

References

  • TEN-STATES-WASTEWATER-2014-SOURCE - Recommended Standards for Wastewater Facilities source pointer
  • WEF-MOP8-7TH-SOURCE - WEF MOP 8 design-reference pointer
  • NFPA-110-2025-EPSS-SOURCE - Emergency and standby power systems source pointer
  • NEMA-MOTORS-GENERATORS-SOURCE - Motors and generators source pointer
  • CRANE-TP410-2022-SOURCE - Pump, pipe, valve, and fitting flow-reference pointer
  • NIST-SP811-B8 - Unit conversion source pointer

Frequently Asked Questions

The local screen divides entered active wet-well volume by entered inflow. For average flow, GPD is divided by 1440 to get GPM. A 500 gallon active volume at 35 GPM gives about 14.3 minutes. Real overflow risk still depends on current level, rim and invert elevations, upstream storage, alarms, response, bypass pumping, and weather.
No. It screens a simplified load using HP × 0.746 divided by motor efficiency, a local 6x starting multiplier, all duty pumps plus auxiliary load, and a 1.25 running-load comparison. Final generator selection requires motor nameplate data, starting method, voltage dip, ATS sequence, NFPA/NEC/AHJ requirements, and supplier/electrical review.
The app shows a local cycle-frequency screen and flags operation near its theoretical maximum. Acceptable starts per hour depend on motor, starter, controls, manufacturer data, wet-well setpoints, heat, maintenance history, and utility practice.
Disclaimer: This screen provides preliminary planning arithmetic only. It is not a pump-station design, generator selection, emergency-response plan, SSO compliance determination, permit document, construction drawing, SCADA/alarm approval, bypass-pumping plan, or substitute for qualified wastewater, electrical, generator-supplier, regulatory, or operator review.

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