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Replacing vanity - odd plumbing

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  • Jan 18th, 2019 12:29 pm
Jul 31, 2017
75 posts

Replacing vanity - odd plumbing

I'd like to replace my powder room vanity. The plumbing is a bit odd. I have supply lines through the floor, and a horizontal drain. I'm not entirely sure what the pipe in the wall of the vanity is, maybe cleanout? I'm not entirely sure how I can get a new vanity in there, even with cutting back the pipes. It's almost as if I'd need to assemble the new vanity in place, piece by piece. Anyone have a similar situation? How did you deal with it?
5 replies
Deal Guru
User avatar
Nov 18, 2005
10810 posts
Another wider angle of the whole vanity might be helpful.

Do you have access to the copper piping below the floor? If so, an option would be to
  • cut off the piping below the floor,
  • add a shut off valve below the floor
  • install the vanity and drill holes from the basement through the base of the vanity
  • install long flexible braided lines up from the basement to the vanity.
Deal Addict
Jan 5, 2003
3797 posts
See photo. Cut the piping by the dotted red line. You'll likely need to redo it anyway to have it line up with the new vanity. Unscrew the flexible supply lines. Then for the new (and old) vanity, cut out the portions of the vanity marked in red. A oscillating multi-tool is perfect for jobs like this. You can then just slide in/out the vanities because you've made big cutouts. It won't look as nice as having perfectly-fitting cut-outs and you'll see a bit of the back wall, but no one is going to see that unless they're looking for spare toilet paper inside the vanity. If cosmetics are important, you can keep the pieces that were cut out, make small cutouts, then wood glue the pieces back in and fill the gaps with some wood putty.

Unless the vanity top is super heavy and the vanity cabinet is super cheap/thin, you're not compromising the strength of the cabinet enough to matter. If you are worried, you can reinforce the inside of the cabinet once it's in place.

Oh, and change those shut offs to use quarter turn valves.
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User avatar
Sep 25, 2003
235 posts
Unfortunately to do this properly would be a little more involved.

If this were my vanity, I would cut the black pipe as it enters the cabinet (assuming there is enough length of pipe from the stub to glue on a coupler), and cut the copper pipes ( after turning off your main water valve!) below your existing valves.

On the new vanity, I would mark the locations and cut the openings for the copper pipes, drain and clean out. The newer faucets I’ve installed have attached flexible braided supply hoses attached. I would extend the copper pipes and solder on new valves to reach the supply hoses.

If you’re lucky you may be able to reuse some of the old drain pipe and p trap depending on how your new vanity drains line up, but it is easier just to replace from the stub to your drain with new pipe material. When attaching your horizontal pieces you need to make sure that you have the proper slope to drain.
Temp. Banned
Dec 19, 2009
3500 posts
Do as zhewie recommends and when you cut the copper cut it 6" from the bottom of the cabinet and you can just slide the new vanity over the water lines. Install two new valves and you can get flex lines at least 36". All you'll need for the drain is a coupling where you cut off the ABS.

Remember to measure twice (or three times) and cut once.
Jul 31, 2017
75 posts
Thanks everyone. I'm going to try replacing it this weekend. Wish me luck!