Moving Bath Tub: Drain and Vent Question

[Peter Dillon]

I am remodeling our bath and moving fixtures to improve the layout. All the fixture drains for the tub and sink are 1 1/2″ copper tied into a 3″ copper main drain. The current sink drain (after the trap) goes into a Tee into 1 1/2″ copper vertical pipe. The vertical pipe goes down for the drain, and also up to connect to the 3″ copper soil stack that vents through the roof. The sink is about 3′ from the main waste line, so the drain goes down through the wall, then makes a 90 degree elbow under the floor and across to just above the main waste, then an elbow down into the line.

My question: Can I replace that elbow under the floor with a Tee, then extend the horizontal portion of that sink drain line under the floor over to the tub? I would also add a similar vent at the tub drain and tie it into the sink vent that goes over to the soil stack.

So, each fixture would have it’s own vent, should be OK, right? Can a sink and a tub share the same 1 1/2″ drain or do they need to be plumbed separately into the 3″ main waste? I know ideally they should be plumbed separately, but the master bath is on the other side of the wall from this bath, and all of the fittings are too close together on the copper waste line to insert another. I’m trying to avoid having to cut out the entire length of main waste and replace with PVC. I’m keeping everything copper since I’m pretty good at soldering.Don 4112008-02-07 02:34:21

[73TorinoParticipant]

Not sure what code you’re under, but here 1-1/2″ wouldn’t work. The drain would have to go to 2″ once the lavatory tied in. In addition, you couldn’t use a tee on its back. You’d have to use a combination wye and 1/8th bend for the connection.73Torino2008-02-25 15:29:37

[Don 411Participant]

Thanks! Where is “here” for you?

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