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
P_{whp} = q h SG / (3960 μ) (1)
where
P_{whp} = 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:
P_{whp} = q dp / (1715 μ) (2)
where
P_{whp} = 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
P_{whp} = (20 gpm) (20 ft) (1) / (3960 (1.0))
= 0.10 hp
Power required to pump water at 60^{o}F with ideal pump efficiency 1.0:
Volume Flow (gpm)  Power (hp)  

Height (ft)  
5  10  15  20  25  30  35  40  50  
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.
Power Consumption in Metric Units
The power consumption for pumping water can be expressed in metric units as
P = q h ρ / (6116 10^{3} μ) (3)
where
P = power (kW)
q = flow (liter/min)
h = head (m)
ρ = density (kg/m^{3}) (water 1000 kg/m^{3})
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/m^{3}) / (6116 10^{3} (1.0))
= 0.16 kW
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