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Q & A: Water friction loss in pipe

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Most recent answer: 02/15/2011
Q:
I need to find out how much water loss due to friction would be in a three foot PVC pipe for seven miles??
- Chet (age 45)
Weed CA USA
A:
I'm guessing you mean how much energy will be lost to friction. That depends on the flow rate.  For moderately low flow rates the energy loss per time is proportional to the square of the flow rate, which means that the energy loss per volume of water transmitted is proportional to the flow rate. The equation you're looking for is the Poiseuille equation:

This includes all the necessary constants to complete your calculation.
Another way to look at this is that the pressure drop along the pipe will be proportional to the flow rate. The energy loss per time is equal to the pressure drop times the flow rate.

Mike W.


(published on 02/15/2011)

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