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Old 01/09/2008, 10:10 PM   #15
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Join Date: Nov 1999
Location: Nampa, ID
Posts: 5,870
Originally posted by not_sponsored
If you're pumping 1200 gph in the pipe, the difference between a 1.5" pipe and a 3" pipe is 2.5 feet of head per 100 feet of pipe. In this case you'll be working with less than 10 feet of pipe or .25 feet less head by switching from a 1.5" pipe to a 3" pipe, TWICE THE DIAMETER.

This is correct.

On the other hand, lets say we have 5 90 degree fittings, for 1.5" pipe that would add 4 feet of head for every 90, or 20 feet of head.

This is not correct. Your table is not in feet of head loss, it is in equivalent feet of pipe, so for the 1.5 inch pipe you would at 4 feet of pipe lenght, so with 5 90s you would now be working with 30 feet of pipe not 10, so the head would be apox .8 30/100 *2.5 feet /100 feet

Using 3" pipe we would add 7.9 feet of head for every 90 or 39.5 feet of head.

For the 3 inch pipe a 90 adds 7.9 feet so 5 times 8 is 40, so we are working with 50 feet of pipe

So 50/100 * .1 equals .05 feet of head pressure.


This is a difference of 19.5 feet for the different sized pipes, for MINOR head loss. Compare this with the .25 feet of head loss caused by decreasing the pipe size in MAJOR head loss.
So once you use the tables correctly you change from .8 feet to .05 feet A difference of .75 feet or apox 1600 percent decrease in friction by going from 1.5 inch to 3 inch pipe at 12000 gph

Please learn how to use your tools.

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