Kitchen Sink Under Window Question

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by jb9, Jun 14, 2021.

  1. jb9

    jb9 Member

    Joined:
    Aug 3, 2015
    Location:
    California
    Sorry for the dumb question but I don't understand something. I constantly read that plumbing pipes should not be placed in exterior walls but rather located inside the conditioned space. Why are there so many kitchen sinks under exterior windows? Are the supply lines kept inside the wall and hidden in the cabinet? Can the DWV be kept out of the exterior wall too? Is the Ptrap really the only place water could freeze and that should be under the cabinet? I'm doing a design and this has always perplexed me.
     
  2. hj

    hj Master Plumber

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    The water pipes can come up through the floor of the cabinet and there is no standing water in the drain lines to freeze. The sinks are put there so the "mother' can see the kids playing in the yard.
     
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  4. Tuttles Revenge

    Tuttles Revenge In the Trades

    Joined:
    Oct 15, 2014
    We install water lines on the most inside part of the wall and insulate between the exterior and the piping. Less risk if its a 2x6 wall, but pretty common even in 2x4 construction. But I'm in a fairly temperate climate in seattle.
     
  5. jb9

    jb9 Member

    Joined:
    Aug 3, 2015
    Location:
    California
    This is helpful. I appreciate these recommendations. I was also thinking the pex would come up into the cabinet box (thanks HJ) and the trap would be down there as well with the arm going into the 2x6 wall and immediately dropping below the floor into the crawler and joining the main. Vent PVC would be the primary DWV in the wall until it returned to the main vent. Climate here is cold so I will make sure I am on the interior/conditioned side of the insulation. I might try drawing what I am describing.
     
  6. Helper Dave

    Helper Dave In the Trades

    Joined:
    May 25, 2020
    Location:
    Wisconsin
    NE WI here. We put exterior water lines though the floor. Drain and vent can be in the wall. No traps in the wall, though.

    Just be cautious/aware that when drilling through window framing (king and jack studs) for your vent and drain, some inspectors will require you to support it with stud shoes.
     
    Tuttles Revenge likes this.
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