Sump Pump Calculator

Calculate sump pump capacity and pit sizing for basement drainage. Determines required pump capacity, total dynamic head, cycle frequency, and verifies motor protection requirements.

Calculate Sump Pump Requirements

For educational purposes only. Not a substitute for professional engineering judgment.

Input Parameters

Inflow Properties

Inflow Rate

GPM

Rate of water entering the sump pit

Inflow Source

Primary source of water entering the pit

Discharge System

Static Head

Vertical lift from pit to discharge point

Discharge Pipe Length

Total length of discharge piping

Pipe Diameter

Internal diameter of discharge pipe

Pipe Material

Material affects friction loss

90-Degree Elbows

Number of 90-degree elbows in discharge line

Check Valves

Number of check valves in discharge line

Sump Pit Dimensions

Pit Diameter

Internal diameter of sump pit

Pit Depth

Total depth of sump pit

Pump On Level

Water level that triggers pump start (from pit bottom)

Pump Off Level

Water level that stops pump (from pit bottom)

Pump Settings

Pump Type

Type of sump pump

Minimum Cycle Time

minutes

Minimum time between pump cycles (motor protection)

Safety Factor

Factor applied to pump capacity sizing

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