new second floor bathroom

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by treefrog, Jun 13, 2009.

  1. treefrog

    treefrog New Member

    Jun 13, 2009

    I am planning the DMV system for a new second floor bathroom. The bathroom is directly above a first floor bathroom (the house is a 50's Cape).

    There is an existing 3" drain/vent stack to which I will be draining the vanity and toilet into (they are on the same wall as each other and the main stack).

    The tub is on the other side of the bathroom. Currently, the vent pipes from the first floor bathtub and kitchen sink run just above the second floor. I will be reventing these.

    My question is:

    Can I drain the tub into the existing vent from the kitchen sink below instead of draining it into the main drain/vent stack?

    Thank you for your reply.
  2. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    Not unless you want to create backups for your kitchen sink.

    Any water coming down the pipe, will either pull the trap seal from the kitchen sink p-trap, creating bad smells,
    Or overfill the sink.

    Vents pipes are not normally even run with waste fittings, knowing that only air move through them.

    The tub could be tied in below the kitchen sink drain, if you run a new waste line and tie it in below the kitchen sink.
    Last edited: Jun 14, 2009
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    You CANNOT drain ANYTHING on the second floor, such as the toilet, tub, shower, or sinks, into the first floor vents. EVERYTHING either has to have its own drain line, or the lower level vents have to revised so the upstairs can use the existing pipes for drains. Neither situation is normally very easy to accomplish.
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