Fluid Flow

Is it possible to calculate the max flow rate (gals/m) achievable through a given piping system with only the following variables?

- 4" SDR 11 HDPE pipe (3.633" ID)
- 28,000 feet of pipe from source to destination
- 90' of elevation change from source to destination
- destination is another pond, pipe is open ended and 90' higher than source.
- 150 roughness value

I'm trying to figure out what size of centrifugal pump to place at the source pond and what flow rate is possible. I'm not very smart about this type of thing. I Googled it, but every calculator I found wanted either velocity or flow rate, which I don't know because there is no pump there yet..? Thank you.

Doug Huffman

Gold Member
When I designed piping systems as an ancillary job, my component catalogues all listed flow loss D/L per component or foot. Use that to model the system - a system diagram - pick your pump characteristic (curve) to intersect the system diagram at your desired flow rate.
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Great, got that figured out. Thanks. Now, I have another question... how would adding another pump in series affect the pressure on the pipe? I understand that with two centrifugal pumps in series, having equal specifications, you would add their head ratings together which would slide the desired flow rate further out on the system curve thereby increasing the flow rate. I guess what I'm trying to get at is to get better flow rate would I put the series "booster" centrifugal pump piggy-backed onto the discharge of the first pump right at the source, or would I be better off to put it a couple miles downstream in the piping system? Putting it in series right at the source pond pump would probably increase the pressure at the outlet of the booster pump so much so that the pipe's pressure rating would be exceeded?

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