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Thread: Venting new main floor bath.. will this work??

  1. #1
    DIY Junior Member EldonP's Avatar
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    Default Venting new main floor bath.. will this work??

    Hi All,

    I'm trying to plan a new bathroom on our main floor that's directly below the one on our main floor. The pictures below say it all, but in essence I'm trying to vent a sink and toilet without running pipes up the wall at the fixture locations. I've got lots of space in the basement to work with, so I've come up with a few ideas.. Will any/all of these work for me?

    In terms of local code, I haven't found a good guide, so I'm trying to wade through the actual code as I can. It looks to me like any of these configurations could arguably meet the maximum length to trap. However, there is a bit in there that says that the vent must attach to the fixture above its flood line. I don't understand how this is possible considering that the flood line of a typical vanity is pretty much level with the outer surface of the vanity.

    As I said, I'm finding the plumbing code opaque, so any advice would be much appreciated!

    Thanks,
    Eldon
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  2. #2
    DIY Senior Member Hammerlane's Avatar
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    Your figure #1 is not effectively venting the sink. I believe you need to pull the vent before the water drops vertical after the trap arm.

    Same with figure #2.

    With figure #3 how long is your tailpiece length?

    One of the real plumbers will be along shortly
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  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    The vent for the lav needs to be at the level of the p-trap and trap arm.

  4. #4

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    none of your sketches will meet code... # 3 is the closest as it is effectively a wet vent (assuming its sized right and fixture outlet is not too long) but in order to wet vent the lav would have to connect via continuous waste & vent....so you will need to vent the toilet separately

  5. #5
    DIY Junior Member EldonP's Avatar
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    From your reply and the others, I see that a vent must take off from above the trap. I'd love to do something like you propose in green, but I'm hoping to avoid running pipe in that location. This exercise may prove that this is impossible, however. We'll see..

    To answer your question, I'd estimate something like a 30" drop between the bottom of the sink and the trap. Is there a restriction on this length? I'll have to take a look at the code for this..

  6. #6
    DIY Junior Member EldonP's Avatar
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    Sorry, not used to the forum format.. That reply was meant for Hammerlane

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    DIY Junior Member EldonP's Avatar
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    Mike, if I understand you correctly, the two issues with #3 are that the toilet needs a separate vent and the drop from the sink to the trap might be too long.

    Here's a new diagram with the toilet vent added. I'll have to look into the sink and toilet drop lengths.. Any keywords I should look out for when I try reading the code?

    I guess another solution would be to put an AAV under the sink, vent the lav per sketch 1, and call it a day?
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  8. #8
    DIY Junior Member EldonP's Avatar
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    A little bit of research reveals that the vertical run maximum is somewhere in the neighborhood of 24" and I'm not kneeling to wash my hands, so looks like AAV it is!

  9. #9
    DIY Senior Member Hammerlane's Avatar
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    Quote Originally Posted by EldonP View Post
    To answer your question, I'd estimate something like a 30" drop between the bottom of the sink and the trap. Is there a restriction on this length? I'll have to take a look at the code for this..
    30" will be too much drop
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  10. #10
    DIY Junior Member EldonP's Avatar
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    Unless anyone figures otherwise, it's looking like this is the way to go.. Or, of course, give up the extra space in this tiny room and run pipes through the walls behind the sink.

    I still need to double check in the code whether the vent between the toilet and the stack is required.. I recall reading somewhere that a vent is required for a toilet when there are fixtures upstairs on the same stack, but this may be a regional thing. Thanks everyone who responded; added a lot to my understanding of the problem!

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  11. #11
    Moderator & Master Plumber hj's Avatar
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    quote; I still need to double check in the code whether the vent between the toilet and the stack is required.

    There is NO question about it. It IS required, and the sink AAV will be ineffective if that vent is eliminated.
    Licensed residential and commercial plumber

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