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scaling copper to pex

Georg Member Posts: 8
Is it correct that I need 2 times the feet of head for 3/4'' pex than for 3/4'' copper?

If I understand the system curve correctly, the required head decreases with the pipe area squared, or the diameter to the power of 4. I measured the inner diameter of copper-M to be about 13/16'', whereas 3/4 pex only has 11/16''. And (13/11)^4 is approximately 2.

Is the difference between pex and copper really that large?


  • Timco
    Timco Member Posts: 3,040

    Check the ID of the pex fittings...waaay less than the pipe...Wirsbo expands, but standard crimp pex ftgs are the same ID as one size smaller copper...or slightly less.

    Just a guy running some pipes.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291
    To a certain point

    That's correct. But, a typical pex run will have virtually no fittings which add considerably on the copper side. When using pex you're usually dealing with what amounts to a straight run of tube.
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