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Thread: rough-in question

  1. #1
    DIY Member idoc4u's Avatar
    Join Date
    Sep 2009

    Question rough-in question

    I am going to relocate my basement toilet drain as well as my shower drain that have been roughed in. It is relatively new construction.

    The shower drain (2") and toilet drain (4") converge and then meet the lav DWV (2") (all PVC). It is a "wet" vent set-up. From there the 2" drains to a back water valve and then to the sewer system. The main stack connects to the back water drain.

    It is my understanding that since the lav DWV is 2" it would function as the vent for the toilet and the shower as they currently do not have their own vents.

    The toilet is 8 feet from the lav DWV, the shower drain is 6 feet from the lav DWV and the lav DWV is about 6 feet from the main stack. The shower is 6 feet from the main stack and the toilet is 11 feet from the main stack. There is a 2" "future vent" available to connect to at the ceiling joist/rim joist area almost directly above the toilet flange.

    My questions are as follows; 1. With a 2" Lav DWV will it serve as vent for toilet, shower and lav? I've read that a 2" Lav DWV can serve as vent for up to 4 fixtures, but I'm not certain of this and would be happy to create auxillary vents for the toilet and shower, if it helps them function better. 2. My understanding is that with a 2" drain the fixture trap should not be located more than 6 feet from the main stack. Is this true or am I ok to use the one Lav vent for all three fixtures since the furthest fixture (4" toilet) will be 8 feet from the Lav vent?

    Does this make sense, or should I send a photo?


  2. #2
    Plumbing Designer FloridaOrange's Avatar
    Join Date
    Dec 2005
    SW Florida


    For it to be wet vented correctly the toilet and the shower would tie into the lav line separately.

    The shower drain (2") and toilet drain (4") converge and then meet the lav
    This sounds incorrect.

    Pictures may help.
    Semi-professional plumbing designer
    Enjoying life in SW Florida


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