What This Solves
Calculates sump pump capacity requirements, pit sizing, cycle frequency, and total dynamic head for basement and crawlspace dewatering.
Best Used When
- You need to select a sump pump capacity based on groundwater inflow rate
- You want to size the sump pit to achieve an appropriate cycle frequency
- You are calculating total dynamic head (TDH) to select a pump from manufacturer curves
Do NOT Use When
- You need to design the foundation drain system that feeds the sump — Use Foundation Drain Calculator
- You need to design a French drain for yard drainage rather than foundation dewatering — Use French Drain Calculator
Key Assumptions
- Groundwater inflow rate is constant (steady-state design condition)
- Total dynamic head includes static lift, pipe friction losses, and fitting losses
- Pump capacity is selected at the operating point on the pump curve (not maximum capacity)
- Cycle frequency is calculated from pit volume and inflow rate to avoid excessive motor cycling
- Check valve prevents backflow when the pump shuts off
Input Quality Notes
Inflow rate is the most uncertain input. Use foundation drain calculations or field measurements during wet season. Size the pump with a safety factor of at least 1.5 above calculated inflow.
Calculate Sump Pump Requirements
For educational purposes only. Not a substitute for professional engineering judgment.
Sump Pump Design Overview
Sump pump design balances pump capacity against inflow rate while ensuring adequate cycle time to protect the pump motor. Storage volume in the pit allows the pump to cycle on and off rather than run continuously.
- Pump Capacity - Must exceed inflow rate with safety factor
- Total Dynamic Head - Static lift plus friction losses
- Cycle Time - Minimum 3 minutes to protect motor
- Duty Cycle - Target less than 50% for longevity
Typical Inflow Rates (GPM)
| Source | Min | Typical | Max |
|---|---|---|---|
| Foundation Drain | 2 | 10 | 30 |
| Groundwater Infiltration | 5 | 20 | 50 |
| Floor Drain | 1 | 5 | 15 |
| Combined Sources | 5 | 15 | 40 |
| Laundry Discharge | 5 | 15 | 25 |
Source: Engineering practice, IPC guidelines
Pump Type Characteristics
| Pump Type | Typical GPM | Max Head (ft) | Description |
|---|---|---|---|
| Pedestal Pump | 40 | 20 | Motor above pit, pump below |
| Submersible Pump | 50 | 25 | Motor and pump submerged in pit |
| Battery Backup Pump | 25 | 15 | DC pump with battery power |
| Water-Powered Backup | 15 | 10 | Uses water pressure, no electricity |
| Combination (Primary + Backup) | 50 | 25 | Primary AC with battery backup |
Source: Manufacturer specifications, engineering practice
Minimum Recommended Pit Sizes
| Pump Type | Min Diameter (in) | Min Depth (in) |
|---|---|---|
| Pedestal Pump | 18 | 24 |
| Submersible Pump | 18 | 24 |
| Battery Backup Pump | 14 | 18 |
| Water-Powered Backup | 14 | 18 |
| Combination (Primary + Backup) | 24 | 30 |
Source: IPC 2021, manufacturer recommendations
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Last verified: February 2026