Ah, but my salesman from ABC pump co sez that his 4 HP pump is more powerful than the 4 HP pump that the XYZ pump salesman is trying to sell.
Which pump would you recommend?
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Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
OK, we know you want an electric motor, not to exceed 4 HP, and "the most powerful".
Do you know what flow rate you would like? What pressure or head?
Do you want a piston, centrifugal, gear, or progressive cavity pump?
What motor speed? 900, 1200, 1800, or 3600 RPM?
Do you want a submersible or piped suction? Flooded suction or self priming?
Are you pumping clear water, sewage, gas, diesel fuel, acid, or some exotic liquid?
Provide some detail of what you are trying to do or solve, and you will be surprised at the advice you will get. If you leave too much to our imagination, well no telling what you will get.
__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.