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Sharing plumbing line across wall for bathroom vanity and kitchen sink

I am relocating my kitchen and want to position the sink on the other side of a wall from where there is a bathroom vanity in order to share the plumbing line of the vanity. Is this possible, or are there different requirements for drains for a bathroom vanity versus a kitchen sink? ? If it is possible, does the position have to be right across the wall, or can the kitchen sink be about a foot or two down the wall from the bathroom sink (on the other side of the wall, of course)? 
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Posted 2018-07-30T13:38:36+0000  by westiegwen westiegwen
Hello westiegwen.  Welcome to the Community!

You can plumb in a second drain to an original vented vertical drain.  I do assume that this drain size inside the wall is 1 1/2" or larger though.  This is because the kitchen sink trap and drain parts will be 1 1/2" and you cannot go smaller in drain size as water flows out through it.  It is possible that your bath drain is 1 1/4" inside the wall and this would be a problem.  In most cases, I have found that the in-wall drain system even for bathrooms is at least 1 1/2".

Measure the height of the bathroom sink rough in outlet.  It should be coming out of the wall around 18-19" off the floor.  Kitchen sink rough in height is usually lower, more like 14-16".  Based on this it might well be possible to just splice a new sanitary tee for the kitchen drain right under the existing bathroom sanitary tee on the same pipe.

If you want to install the kitchen sink a foot or two down the wall from that original bath drain, then it would be a fairly easy process to plumb that in as well.  You will need to vent your new kitchen sanitary tee though.  I have drawn a simple illustration of how you could do this.

Posted 2018-07-31T17:10:37+0000  by Chris_HD_CHI
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