Shower Drain P-trap

Discussion in 'Shower & Bathtub Forum & Blog' started by Jersey#1, Mar 29, 2014.

  1. Jersey#1

    Jersey#1 New Member

    Mar 29, 2014
    Hello All,
    Just wondering if the P-trap from a shower drain has to be right under the shower or can it be further down the line? My bathroom is built over a crawl space and even though it is insulated I don't like the Idea of putting a p-trap out there under the shower where its not accessible and has standing water. I was going to put the P-trap in the basement area next to the main sewer line about 42" from the drain. It would also get its venting from the sewer line..... is that to far of a run for the drain.

    Can anyone shed some light on this for me from a code perspective.

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Not a great idea. Keep in mind that a drain line can have more than sewer gasses that make smells...just the inside of the pipe can accumulate some hair, oils, soap scum, etc. in it. Having 42" of that before the trap may end up smelling as bad or worse than a dry trap. If the crawl space gets that cold, you should think about closing it up a bit to stop the air infiltration, and that normally would keep it from freezing. If there's insulation, you might build a box and have the trap on the floor side - IOW, insulation below the trap to allow the room above to help heat that area. The normally dry trap arm shouldn't be an issue with the hot shower water running through it and if sloped properly, will drain before it would become an issue with freezing.
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  4. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    I've almost never seen a pipe freeze in a crawl space. I have see pipes freeze plenty of times above the crawlspace.
    Put the p-trap where it should be. In the crawl space, right under the drain.
  5. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

    Jul 20, 2009
    Design Work World Wide: Bathrooms Vancouver Area
    North Vancouver, BC
    Not really sure what the code books say for placement.

    I'm with Terry on placing it under the drain if you can. Have you considered using a pipe warmer if your scared about freezing?

    The furthest I have ever seen a P-Trap from a shower is about 24". I see much more on occasion from 2" - 10" away from the drain.

    If you are really neverous try something like this

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