Sump Pump Sizing Guide

Sump pumps remove accumulated water from sump basins in basements, crawl spaces, and underground structures. Proper sizing requires estimating inflow rate, sizing the basin to prevent short-cycling, and calculating TDH for pump selection. Plumbing Booster's Pumps module supports multiple sump source types.

1. **Determine inflow rate** - From drainage fixture units, area drainage, or manual design flow. 2. **Select source type** - Sanitary drainage, storm drainage, fire protection drainage, or fire sprinkler system. 3. **Size basin** - Volume must provide minimum cycle time to prevent excessive motor starts. 4. **Calculate cycle time** - Cycle = Basin Volume / (Pump Rate - Inflow Rate). Minimum cycle time depends on motor size and allowable starts per hour. 5. **Calculate TDH** - Static head (lift) + friction losses (discharge piping) + residual head. 6. **Select pump** - Must pump at TDH at a rate exceeding inflow rate. 7. **Check N+1 redundancy** - For critical applications, provide standby pump.

Basin volume is critical for pump longevity. Too-small basins cause rapid cycling (short-cycling), which burns out motors. Rules of thumb: - Minimum cycle time: 5 minutes for small pumps, 10-15 minutes for larger pumps - Maximum starts per hour: 6-10 (varies by motor size) - Basin volume = Pump Capacity x Cycle Time / (1 + Pump Capacity / Inflow Rate) Example: Inflow = 10 GPM, Pump = 50 GPM, desired cycle = 10 min Basin Volume = 50 x 10 / (1 + 50/10) = 500 / 6 = 83 gallons (~11 cubic feet)

Plumbing Booster supports four sump source types: - **Sanitary drainage** - DFU-based inflow from drainage fixture units - **Storm drainage** - Rainfall-based inflow from roof/area drainage - **Fire protection drainage** - Drainage from fire suppression test/discharge - **Fire sprinkler system** - Test/drain point flow with count and flow per point

In the Pumps module, select "Sump" as the pump system type. Choose source type and enter parameters. The software calculates inflow, sizes the basin, checks cycle time, calculates TDH, and recommends a pump arrangement. Validation warns about short cycling, insufficient basin volume, and excessive starts per hour. The sump pump model uses a physical cycle-time calculation based on basin geometry, inflow rate, and pump capacity rather than empirical rules of thumb.

- **IPC Section 712** - Sump pump and ejector requirements, including basin sizing, pump capacity, and discharge piping provisions. - **ASPE Plumbing Engineering Design Handbook Volume 2** - Sump and ejector pump design methodology, including cycle-time analysis and basin sizing procedures. The software's sump pump calculations are reviewed against these references. Project-specific code compliance (local amendments, authority having jurisdiction requirements) must be verified by the design engineer.