# Pumping Water - Required Horsepower

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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