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Pumping Water - Required Horsepower

Horsepower required to pump water.

Energy imparted to water by the pump is called water horsepower - and can be calculated as

Pwhp = q h SG / (3960 μ)                            (1)

where

Pwhp = water horsepower (hp)

q = flow (gal/min)

h = head (ft)

SG = 1 for water Specific Gravity

μ = pump efficiency (decimal value)

Horsepower can also be calculated as:

Pwhp = q dp / (1715 μ)                   (2)

where

Pwhp = water horsepower (hp)

dp = delivered pressure (psi)

Example -  Horsepower Required to Pump Water

20 gallons of water per minute is elevated 20 ft. The horsepower required (ex. friction loss in piping and efficiency = 1.0) can be calculated as

Pwhp = (20 gpm) (20 ft) (1) / (3960 (1.0))  

        = 0.10 hp 

Power required to pump water at 60 oF with ideal pump efficiency 1.0:

Pumping Water - Power vs. Head and Flow
Volume Flow
(gpm)
Power (hp)
Height (ft)
51015202530354050
5 0.00631 0.0126 0.0189 0.0253 0.0316 0.0379 0.0442 0.0505 0.0631
10 0.0126 0.0253 0.0379 0.0505 0.0631 0.0758 0.0884 0.101 0.126
15 0.0189 0.0379 0.0568 0.0758 0.0947 0.114 0.133 0.152 0.189
20 0.0253 0.0505 0.0758 0.101 0.126 0.152 0.177 0.202 0.253
25 0.0316 0.0631 0.0947 0.126 0.158 0.189 0.221 0.253 0.316
30 0.0379 0.0758 0.114 0.152 0.189 0.227 0.265 0.303 0.379
35 0.0442 0.0884 0.133 0.177 0.221 0.265 0.309 0.354 0.442
40 0.0505 0.101 0.152 0.202 0.253 0.303 0.354 0.404 0.505
45 0.0568 0.114 0.170 0.227 0.284 0.341 0.398 0.455 0.568
50 0.0631 0.126 0.189 0.253 0.316 0.379 0.442 0.505 0.631
60 0.0758 0.152 0.227 0.303 0.379 0.455 0.530 0.606 0.758
70 0.0884 0.177 0.265 0.354 0.442 0.530 0.619 0.707 0.884
80 0.101 0.202 0.303 0.404 0.505 0.606 0.707 0.808 1.01
90 0.114 0.227 0.341 0.455 0.568 0.682 0.795 0.909 1.14
100 0.126 0.253 0.379 0.505 0.631 0.758 0.884 1.01 1.26

Note! Individual pump curves should always be used for exact calculations.

horsepower required to pump water to various heights

Power Consumption in Metric Units

The power consumption for pumping water can be expressed in metric units as

P = q h ρ / (6116×103 μ)                            (3)

where

P = power (kW)

q = flow (liter/min)

h = head (m)

ρ = density (kg/m3) (water 1000 kg/m3)

μ = pump efficiency (decimal value)

Example - Power Required to Pump Water

The power required to pump 100 l/min water an elevation of 10 m (ex. friction loss in piping and efficiency = 1.0) can be calculated as

  P = (100 liter/min) (10 m) (1000 kg/m3) / (6116×103 (1.0))

     = 0.16 kW

power required to pump water to various heights - kW, liter per. min, meter

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