How Much Horsepower Do Pump Engines / Motors Need?

Water pump on truck trailer

How much horsepower do pump engines need? The answer to this question depends on the product’s specifications as well as on the type of application. For example, wellpoint pumps that are used for construction dewatering operate differently than axial and mixed flow propeller pumps, which are often used for storm water control and agricultural applications. Below, we provide a brief glimpse into the requirements of a pump and its engine to explain how to determine the right pump and horsepower for the job.

Selecting a Pump

Large-Hydraflo-drive-unit-6-14-18-A-webFirst, you’ll need to determine your liquid flow needs and the lift or pressure required to get the liquid to the destination. The discharge pressure, or “head”, and/or if the liquid is aerated, indicates the type of pump to be used. Some examples are axial flow, mixed flow, radial flow, and positive displacement. All pumps need to be driven by a prime mover such as an electric motor or a fueled engine which includes diesel, natural gas, gasoline, etc. 

The prime mover’s required size (power rating) is based on the liquid flow rate, the liquid’s density, the pressure head developed, the efficiency of the pump and drive system, and any service factors applied.

Understanding Horsepower and Units of Measurement Selecting a Pump

Engine/motor horsepower is determined by:
1)      Flow rate (Q) for example gallons per minute (GPM), cubic ft per second (CFS), cubic meters per sec (CMS)
2)      Discharge head (H) for example feet (F), pounds per square in (PSI), meters (M)
3)      Specific Gravity (SG)
4)      Efficiency of the drive system and pump (EFF)
5)      Service Factors (SF) for example overload avoidance, impacts, cavitation, suction vortex, altitude
6)      Units conversion factor (C)
power equation

A Quick Introduction to Engines and Tiers


If you’re working with equipment that depends on non-road diesel engines, you should know that they still need to meet emissions standards. In the United States, there are four categories or “tiers” of emissions standards, and each tier has different requirements to reduce air pollutants — essentially, the higher the tier, the more stringent federal agencies’ regulations become. The United States currently requires all non-road diesel engines to meet Final Tier-4 emissions standards on units rated < 750hp (560Kw). MWI works with reputable companies to provide properly sized engines/motors for their water pump application needs. We rent and sell our products worldwide. 

If you have questions about any of them, our team offers free guidance and estimates. 
Simply call us at 772-770-0004, and we’ll be more than happy to help.