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Dewatering Pump Calculator

Calculate dewatering pump requirements including inflow rate, pump capacity, horsepower, and discharge pipe sizing for excavations.

Inputs

sq ft
ft
ft/min
ft
ft

Results

Seepage Inflow

80.28 GPM

Required Pump Capacity

120.42 GPM

Pump Horsepower0.56 HP
Number of Pumps1
Discharge Pipe Size3 in
How to Use This Calculator
  1. Enter Excavation Area in sq ft and Depth in feet to define the volume to dewater.
  2. Set Soil Permeability — higher permeability (gravel/sand) means faster inflow and a larger pump.
  3. Enter Pumping Distance (ft) and Total Head to account for pipe friction and elevation.
  4. Read Required Pump Capacity (GPM), Pump Horsepower, and Number of Pumps to spec equipment.
  5. Use Discharge Pipe Size to size the discharge header and plan site drainage.

How the result changes with Excavation Depth

Excavation DepthSeepage InflowRequired Pump Capacity
513.38 GPM20.07 GPM
18187.33 GPM281 GPM
33388.04 GPM582.06 GPM
45548.61 GPM822.92 GPM

What each input means

Excavation Area
Plan area of the excavation.
Excavation Depth
Depth of excavation below grade.
Soil Permeability (k)
Hydraulic conductivity of the soil (sand: 0.01-0.1, clay: 0.0001-0.001).
Water Table Depth
Depth of the water table below ground surface.
Discharge Distance
Distance from pump to discharge point.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Excavation Area = 2000, Excavation Depth = 10, Soil Permeability (k) = 0.01, Water Table Depth = 4 = 5 input(s) provided
  2. Calculate Seepage Inflow
    Seepage Inflow
    80.28 = 80.28
  3. Calculate Required Pump Capacity
    Required Pump Capacity
    120.42 = 120.42
  4. Calculate Pump Horsepower
    Pump Horsepower
    0.56 = 0.56
  5. Calculate Number of Pumps
    Number of Pumps
    1 = 1

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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