Does anyone know how to properly size a pump for my application? 70foot head= 1000 foot of 2" discharge pipe= would like to have around 50GPM at the discharge end. I plan to use a centrifugal pump at the creek to pump water to my pond. The pump I am looking at is 5hp 230v 175gpm @ 70ft.head. With the friction loss will I be able to get what I need at the discharge end?

-- Maurice A. Price (maprice@nr.infi.net), December 01, 2000

Answers

Maurice, I'm concerned that it's not the right pump, but can't tell without more data. Assuming you're using schedule forty pvc pipe, the pump will have to overcome 4.58 feet of head loss due to friction per 100 feet. In other words, 45.8 feet of head for 1000 feet.

I THINK you are saying that the pump will have a total lift of 70 feet, right? So the pump will have a total head (static and dynamic) of 70+45.8=115.8 feet.

Without seeing a power curve for the pump, I can't say if it could do this or not. But it seems likely that you should either have a smaller horsepower pump, or a bigger pipe. Look at the power curve--each pump needs to be the right design for each situation.

That same pump could pump 175 gpm with less friction loss (only 18 feet for 1000 feet), if you increased the pipe size to 4".

Basically, what you would be doing with the 2" pipe is wasting two thirds of your power (or two thirds of your potential water) to friction. You should try finding a 1 1/2 or 2 h.p pump to do the job, or put in bigger pipe. Don't forget that a five horse pump will also need a larger power supply, and larger wire than a smaller pump.

JOJ

-- jumpoffjoe (jumpoff@echoweb.net), December 02, 2000.