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Thread: Clothes washer rough-in

  1. #1
    DIY Senior Member DavidTu's Avatar
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    Dec 2009
    Seattle, WA

    Default Clothes washer rough-in

    OK since I posted the PDF from Lincoln County (see thread here) I have a question stemming from the Washer Rough-in on Page 11. (see link here)

    He indicates that the P-trap should be between 6"-18" off the floor. I was aware that the standpipe s/b between 18"-30" off the floor, but not about the P-trap.... what is the purpose of that requirement (what are they trying to prevent)?

    Also, where is the measurement of the P-trap height taken from--where it enters the drain line? or the bottom of the P? or what? (and what if it's a horizontal drain line?)

    Finally, is it OK for the cleanout to be in the 1.5" vent? or need it be 2"? (I actually didn't realize a CO was necessary at all, b/c I figured they could just snake down the SP, but apparently the snake cannot get thru the P-trap--is that right?

    Thanks in advance!

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    The p-trap measurement is from the floor that the washer sits on.
    From the floor to the center line of the trap arm.
    The trap is supposed to be on the same floor as the washer.
    Most inspectors like cleanouts to be the same size as the pipe it serves.

  3. #3
    Nuclear Engineer nukeman's Avatar
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    Nov 2009


    The 18"-30" is the height of the SP above the trap weir. They list the 6"-18" off the floor mainly to get the SP high enough without the SP being too tall. If the trap was put bellow the floor and you used the 30" max SP length, the SP would end up like 20-24" off the floor (too low). From what I've seen, the SP is usually set above the flood rim of the washer (bottom of washer outlet box ~42"). Then say you use a 30" SP height and that will put your trap at 12" above the floor.

    Here, we are allowed to go longer than 30", but I kept mine at 30" since it would meet both codes and was plenty easy to implement it this way.

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