Calculating Brake Horsepower

Distribution operators must be able to calculate the amount of horsepower their pumps are giving in certain conditions –– either water, brake or motor horsepower. In the problem below, look at brake horsepower.

What is the brake horsepower (BHP) for a pump with the following parameters?

Pump Efficiency 74%

Total Head 194 feet

Flow 1.75 MGD

The problem is asking for brake horsepower. Pick out the formula that is needed. In this problem, look for the formula that will solve for BHP.  The BHP formula is in the upper right corner of the formula sheet found on our website under the test preparation materials page.

BHP 1Now the flow in GPM is needed, total feet of head and Ep (pump efficiency).

Using what has been given in the problem, do the necessary conversions to get the numbers in the required units.

To convert MGD to GPM, use the following:


To change the pump efficiency to a decimal, divide by 100:


Brake horsepower (BHP) is the measure of an engine’s horsepower before the loss in power caused by the pump. This gives the operator an idea of what size pump or the amount of horsepower is needed to move the required amount of water with the best efficiency.

To try out a practice problem, checkout Test Your Knowledge – Calculating Brake Horsepower .

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  1. Pingback: WHAT CONDITION THE PUMP'S CONDITION IS IN - The Process Technology and Operator Academy

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