Lift Station Calculator - Pump Cycles, Backup Power & Overflow Risk

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 generator sizing calculations. The calculator estimates starting current, running load, and total power demand.

3. Configure Backup Power

   Enter generator tank size or let the calculator recommend a generator kW rating based on pump motor sizes and building loads.

4. Check Overflow Risk

   See the prominent time-to-overflow display for both average and peak flow conditions. Red warnings appear when time is less than 2 hours.

Built For

• Collection system operators evaluating overflow risk during power outages
• Public works directors sizing portable or permanent generators
• Engineers designing new lift stations with adequate wet well volume
• Emergency planners estimating response time requirements
• Operators tracking pump cycles for maintenance scheduling

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 sizing assumes a 6x starting current multiplier for across-the-line motor starting
• Fuel consumption is estimated at 0.07 gallons per kWh for standby diesel generators under load
• Time to overflow is calculated from the rim of the wet well or the lowest gravity sewer invert, whichever is reached first

Limitations

• Does not model inflow and infiltration (I/I) surges during rain events, which can increase inflow 3-10x above average dry weather flow
• Pump cycling calculations assume constant inflow — peaking factors for morning and evening peaks are not applied automatically
• Generator starting load analysis is simplified and does not account for soft starters, VFDs, or reduced-voltage starting methods
• Does not evaluate force main hydraulics (friction loss, air release, surge protection) that affect actual pump discharge rate
• Overflow risk during extended outages does not account for emergency bypass pumping or tanker truck response
• Does not calculate SCADA alarm setpoints, telemetry requirements, or notification cascade for overflow prevention

References

• WEF Manual of Practice FD-1 — Existing Sewer Evaluation and Rehabilitation (I/I assessment and overflow prevention)
• Hydraulic Institute Standards — Pump Station Design for Municipal Applications
• EPA CMOM (Capacity, Management, Operations, and Maintenance) — Guidance for Sanitary Sewer Overflow Prevention
• NFPA 110 — Standard for Emergency and Standby Power Systems (generator sizing and testing requirements)
• Ten States Standards — Recommended Standards for Sewage Works (lift station design criteria)
• WEF Manual of Practice No. 8 — Design of Municipal Wastewater Treatment Plants (pump station design chapter)

Frequently Asked Questions