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interplexr 10-05-2012 07:57 PM

Rerouting vanity drain line - Options?
We are going to redo a bathroom which occupies a dormer on our cape cod style house. The current vanity is in an alcove and is a built in.

We are going to be replacing it with a furniture style vanity so it won't but up against the walls on the sides.

The wall the vanity butts up to is an exterior 2x4 wall. The copper lines are run through this wall and stub out into the back of the existing vanity. They will work fine for the new vanity as well.

The sink drain however is run into the wall on the right instead of the wall in the back since it was a straight shot to the house vent stack which runs through the wall on the right to pick up the bathroom below and the shower on the other side of the wall.

Since the new vanity won't butt up against the side walls, this isn't an attractive option not to mention it would screw up the drawers of the new vanity.

I was wondering what our options might be? Can the sink drain be relocated into the exterior wall and then run sideways to the side wall where it can then turn and tie into the vent stack? Could the sink drain go down through the floor and then parallel the joists to tie into the vent stack? We're redoing the floor for tile so it won't be an issue getting into the space. I'd appreciate any thoughts you have.


TheEplumber 10-05-2012 08:14 PM

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Either way you do it will be challenging. If you go through the floor, you will have to re-vent back. I'd consider the wall option. You already have a vent, you'll just have to rotate the tee at the stack. Hopefully it's plastic pipe- easier to work with.

interplexr 11-08-2012 07:59 PM

I finally cut a hole in the wall to the right of my vanity to see what the vent and drain pipe situation looked like. It looks like another vent line is to the left of the one I'm wanting to relocate. If I go back in to the back wall and try to go around, I would have to go through this vent I didn't know was there..... Can it be used for the sink instead? Is there a limit to how many sinks can go to a single 1 1/2 inch vent? I could go into the back wall and turn and run past the in the way line befor 90ing back towards the existing drain/vent. I would have to take an additional 45 degrees to angle back to the line I'm in now since I went further down the wall to get past it. The other side of this vanity side wall is a fiberglass shower surround so it's open on the other side of the 2x4s where these lines are located. I'm believe I'm to a point where I'll definitely need some professional help to deal with this but I'd like to have an idea of what my options are so I can speak intelligently with them.

TheEplumber 11-08-2012 08:24 PM

199 Attachment(s)
I would like to help you resolve this but to be honest, I gave up trying to visualize what you've got. A picture works much better :thumbup:

interplexr 11-10-2012 07:29 PM

Here is what I have. I want to turn the drain 90 degrees go back into the wall and then 90 to the right, go through the wall and since that line on the left is there I would have to go past it and then 90 then 45 back to get to the line it's in now. The T would be rotated to meet the rerouted pipe. Is that something that can be done? Since there is a fiberglass tube/shower surround on the otherside of the exposed wall, there is a good sized cavity on the other side of those pipes and studs.

TheEplumber 11-11-2012 12:10 AM

199 Attachment(s)
Yes, you can though most plumbers will frown at the number of horizontal 90's.
Use long sweep 90's when running horizontal pipe.
When connecting to the existing vertical pipe use a 90 and a 45 instead of two 90's- better flow.
You should also put an AAV after your trap since it doesn't appear to be currently vented- or is that a tee in the shadows- I can't tell. If its a tee with a vent off the top then angle it back at a 45 degree and use another 45 to clear the stud- if vented forget the AAV
Hope that makes sense

interplexr 11-11-2012 06:36 AM

Thanks for the information! I was hoping something like that would be ok. That connection at the vertical pipe is a tee. It continues up to vent at the roof.

interplexr 11-12-2012 06:17 PM

Turns out I don't have enough room to connect back to the same 1 1/2" line. What is the limit on the number of fixtures that can be tied to a 1 1/2" line? I'm wondering if I can tie into the other line which drains/vents the sink and tub from the bathroom below. Can I have 2 sinks and a shower on one 1 1/2" drain? I tried looking around the internet but got more confused. It made it seem like I have to much on the lines as it is.... :wink:

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