Horizontal pipe size for kitchen and laundry

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Rocknroj, Dec 19, 2019.

  1. Rocknroj

    Rocknroj Member

    Joined:
    Dec 30, 2008
    Location:
    Washington
    I am wondering if I should upsize an existing 2" horizontal (ABS), nicely pitched that serves both my kitchen and clothes washer.. There is a new 2" wash machine drain. 1 1/2 kitchen, running horizontal then connected
    to a 2" line that runs about 30 ft before connecting to 3".

    based on fixture units i realize that the 2" is fine. As a matter of practice should the 2" be upsized to 3"? Or is 2" better than 3" for keeping the pipe clean?

    [​IMG]

    thanks in advance
     
  2. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    Washington State with UPC code is okay with 2" for a sink and washer.
    Some codes like to see 3".

    Sinks are 2" with a 2" cleanout and 1.5" for trap and vent.
     
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