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Thread: Hooking new toilet to stack on 1st floor, below existing bathroom

  1. #1
    DIY Junior Member dayster's Avatar
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    Default Hooking new toilet to stack on 1st floor, below existing bathroom

    Our house has a bathroom on the 2nd floor only. It was remodelled in the past, and all fixtures (toilet, tub, lavatory) drain through the main stack. I am planning to add a new bathroom below it on the first floor.

    The new toilet will be within 4 feet of the existing stack. Keeping in mind that there is a toilet, tub, and lavatory from the second floor above hooked to the main stack:

    -do I need a vent for the toilet or is this close enough to the main stack that it functions as a vent?

  2. #2
    Plumber jimbo's Avatar
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    You must vent the toilet.

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

    It makes no difference how close it is to that pipe, that pipe is not a vent so you have to install a separate vent for the toilet.

    Last edited by Terry; 06-20-2007 at 06:19 PM. Reason: added picture

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    DIY Junior Member dayster's Avatar
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    Quote Originally Posted by hj
    It makes no difference how close it is to that pipe, that pipe is not a vent so you have to install a separate vent for the toilet.
    Thanks for clarifying that.

    I know that the toilet on the upper floor does not have a vent, I presume this is OK since the stack above the highest fixture is considered a vent. Yes?

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    Forum Admin, Expert Plumber Terry's Avatar
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    If you have a pipe going from the lower floor, through the roof, and there is a tee and a 90 el for the upstairs toilet, then the part above the tee, would be a vent, the part below the tee would be a "waste stack"

    A "waste stack" can not be used for a vent. That means NO.
    You can run a separate "vent" up to the second floor, and tie into the vent at 42" above the 2nd floor.

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    DIY Junior Member dayster's Avatar
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    Gotcha. Thanks Terry, your site is very helpful.

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    DIY Junior Member dayster's Avatar
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    As I plot my "vent strategy", I have a number of options to consider utilizing the existing vent pipes (to avoid new holes in the roof and a number of other unpleasant options).

    One option is to vent the new toilet up into the main stack ABOVE the entry point of all other fixtures. This itself I know is fine. However, the restriction is that the 4x2 vent tee would essentially be right on top of the 4x4 sanitary tee through which the other fixtures connect. So, there would not be much vertical seperation between the entry point of the vent in the stack, and the entry point of the fixtures in the stack.

    I suspect that some separation is ideally desirable. However, I think this will work fine from a functional standpoint.

    Comments definatley appreciated.

    Cheers.

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default vent

    The vent HAS to tie into the main vent at least 42" above the upper floor, not just above the other drain connections.

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    Commercial Plumber markts30's Avatar
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    Quote Originally Posted by hj
    The vent HAS to tie into the main vent at least 42" above the upper floor, not just above the other drain connections.
    what HJ is saying is that the vent tie in has to be a minimum of at least 6" above the flood rim of the highest fixture draining into that stack... That is where this magic 42" number is coming from....
    You can tie it in in the wall at +42" or higher or in the attic before it exits the roof....

  10. #10
    DIY Junior Member dayster's Avatar
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    Thanks hj and markts30. I figured that would be the answer.

    So, here's my last option for your comments:

    The first floor bathroom is in a 1-storey addition, hence, it has its own roof that is only 1/2 of the total height of the main house. I could give the toilet its own dedicated vent 2" vent through this 1st floor roof.

    The result would be the main stack venting through the main house 2.5 storeys high, and this second new vent venting @ 1 storey high. Is there any problem with terminating outdoors at different elevations?

    Cheers,
    dayster

  11. #11
    Commercial Plumber markts30's Avatar
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    There is not a problem - just make sure the vent is at least 10' away from any openable window or other air intake...

  12. #12
    DIY Junior Member dayster's Avatar
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    Thanks to all for the help.

    Happily, I have located an existing 2" vent that i can use! It used to be a drain line, but's been disconnected from that purpose and capped, so I'm good to go now.

    Cheers, Dayster

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