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Thread: * Please Critque my Plumbing Design

  1. #1

    Default * Please Critque my Plumbing Design

    I'm finishing the upstairs to my loft above the barn (separate building from
    my main house). There is no plumbing there now.

    Please look at these 2 designs, tell me which one (or neither) is good:

    A few particular questions:
    * It will be a sob (but doable if absolutely needed) to run that long vent from
    the kitchen sink to main vent stack in Plan B - will the AVV in plan A work?
    * Since the toilet and lav are so close to the stack do they need a
    separate vent - is the 4 1/2 feet distance on the lav within 'critical distance'
    to stack so I won't need a separate lav vent, or do I still need one?
    * Is it ok that the vent stack and the sewer stack are offset by approx.
    9 inches (vent stack is to the left of sewer stack, so will it be able to properly
    ventilate toilet?

    Thanks in advance for all advice.
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  2. #2
    Master Plumber master plumber mark's Avatar
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    Talking plan B looks best

    of course it all depends on where you are located in the USA...


    plan B looks best to me,

    but you could live without the
    vent to the kitchen with B, just put an auto air vent
    as the shower shows it would already be vented..

    maybe run 2 inch to the lavatory from the toilet
    and then a 1 1/2 vent above

    bigger is always better for the drain lines


    let the debate begin

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default plumbing

    That has to be the most complicated way to install the piping, and the lavatory needs a trap regardless of how close it is to anything else. You cannot use the "S" trap you show. As far as the sink goes why aren't you just extending it out the roof instead of returning it to the bathroom?

  4. #4

    Default why no kitchen vent

    HJ -

    I know mentality has changed and the std design now is, vent , vent vent...
    but if I put a vent in for kitch sink, that's another hole in the roof - like to keep
    holes in the roof to a min. Also, (I live in Connecticut), do I really need
    another trap for the lav and kitch sink (other than the std. 'under cabinet'
    trap) - my current house just has the under cabinet traps and all works fine -
    no 'poop' fumes coming up anywhere.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default vent

    The mentality has never changed. It has always been.
    1. Connect vents together before going out the roof.
    2. If that is not possible run individual vents out the roof.
    3. As a last resort and only when all else fails, use an AAV. And when the sink does not drain, do not immeditately suspect that it is plugged because the problem could be a long way away and have nothing to do with the sink's drain.

    Every sink/lav needs an "inside the cabinet" trap, it just cannot be like the one you show in your drawing. You do not want two traps on the same fixture or it will not drain. But you really need to have a good plumber arrange the piping for you. You have a lot more fittings than needed, and a couple of other situations that may or may not be a factor depending on how closely you follow your drawing when the pipes are installed.

  6. #6
    DIY Member rombo's Avatar
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    Default

    here you go, may be different where you live but this will work. and remember to add slope to the piping
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    Last edited by rombo; 05-12-2008 at 06:01 PM.

  7. #7
    DIY Junior Member SuperDaddy's Avatar
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    Default

    Quote Originally Posted by hj View Post
    The mentality has never changed. It has always been.
    1. Connect vents together before going out the roof.
    2. If that is not possible run individual vents out the roof.
    3. As a last resort and only when all else fails, use an AAV. And when the sink does not drain, do not immeditately suspect that it is plugged because the problem could be a long way away and have nothing to do with the sink's drain.

    Every sink/lav needs an "inside the cabinet" trap, it just cannot be like the one you show in your drawing. You do not want two traps on the same fixture or it will not drain. But you really need to have a good plumber arrange the piping for you. You have a lot more fittings than needed, and a couple of other situations that may or may not be a factor depending on how closely you follow your drawing when the pipes are installed.
    Can you point out where he has two traps on one fixture for me? I am trying to familiarize myself with plumbing and would appreciate a clarification. Thanks!

  8. #8

    Default reply - no s traps

    super daddy -

    i got lazy drawing my figures - thee are no s traps - i will
    have a drain coming from the sinks, connected to a p - trap - i just
    drew an s to quick

  9. #9

    Default rombo - thanks

    thanks for the drawing- quick question (i am a newbie to plumbing) -
    i read everywhere that s traps arent allowed - ok i understand that for sinks since
    i'll use a p-trap, but what type of trap do i use under a shower?
    (you drew an S, which is the only type of trap i could think of that works
    for a shower).

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Default Dwv

    Rombo's drawing can be simplified even further. There aren't 2 traps yet, but when he asks if he needs one in addition to the undercabinet one, that implies that he might be thinking about doing it, if he doesn't understand what is being told to him. A shower would be the one place where it would be difficult to install an "S" trap, and there is no situation where one HAS to be used.

  11. #11

    Default P trap under shower

    hj -

    thanks for feedback. i can just use a p-trap under the shower
    too, right?

    another quick question - i dont plan on doing this, but....
    some other homes i've seen have an s trap under the sink (lav for example)
    - (on 1st flr) they just ran the drain straight down from basin - into an S
    then straint down through BOTTOM of cabinet to main line below - didnt
    run it into a wall via a p-trap. is this totally un-allowed now- do all
    laves have to drain into a P in the wall - again i'm not planning on doing this,
    just trying to expand my knowledge base

  12. #12
    DIY Member rombo's Avatar
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    Default

    I didn't draw an s trap it is a p-trap connecting to wye. it represents the pipe coming off the wye on a 45

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