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dtweiss74 10-21-2012 11:02 AM

Installing new Vent pipe for kitchen sink
Hi all, I'm new here and proud to be a member!

I'm moving my kitchen sink to an exterior wall. About 4 ft away is an existing 1 1/2" copper drain vent in which a utility sink and washer feeds into down below in the basement. The vent is about 8 " from the wall and must be moved in order to get my cabinets in. I need to move this drain vent to an exterior wall, as well as tie in my new kitchen drain. My plan:

Cut the 1 1/2" copper below the floor in my basement and install a 45 degree rubber to ABS fitting. This will allow the drain to head up through an exterior base plate and resume upward through the ceiling, then another 45 degrees to tie back into the old vent pipe.

Questions: (which i couldn't find online)

Does IPC allow me to go from copper to ABS? I assume yes.

Can I resume the vent through the ceiling, which will now also be a drain for the new kitchen sink, with 1 1/2" ABS?

The 1 1/2" existing copper drain/vent comes straight out of my slab in the basement. Instead of tearing up the slab, can I just use 1 1/2" ABS instead of upping it to 2"?

Here's an example of what we have here...

1 1/2" copper vent/drain coming from slab all the way through the roof to vent. At about 12" above the slab a drain is tied in for our utility sink and washing machine.

What I intend to do.... (is this allowable?)

Cut the copper just below the main level floor to install a 45 degree copper to ABS fitting. Install 1 1/2" ABS at that point in a stud bay on exterior wall up through ceiling and into attic. Then, another 45 degree ABS to copper fitting to tie back into the existing copper vent (to avoid cutting and patching roof for new vent hole). I will then install an ABS wye fitting for the new sink drink which will be about 4 ft from the new ABS vent. This too will be 1 1/2".

Any thoughts out there? Will all be okay? My main questions is: Can I stick with 1 1/2" ABS? I've read that 2" is the norm. However I can't see it allowing to tie a 2" ABS into a 1 1/2" copper in my basement.


DannyT 10-21-2012 02:11 PM

legally you can't tie your drain to a vent that serves fixtures on the floor below.

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