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:
| 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 / (6116×103 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
