I am renovating the bathroom. The drain for the vanity is coming through the floor rather than out the wall (see example photo).


I would prefer a drain rough-in to come out the wall. I think it is cleaner looking and easier to install the vanity later.

In looking in to why it had been done that way I see there is a double floor joist under that partition similar to the diagram below.



I had a previous experience with this exact situation. I just got done with the other bathroom that had the same situation, but in this case the plumber notched the very top of the beam allowing the drain line to hug the beam and run a 45 degree fitting through the notched spot. This got the drain line in to the wall. Something like this photo.


I think the plumber did something like this-


This house was built in the 80's. Is this acceptable today? Or should I just leave the drains coming out of the floor?

 

A double beam would mean it is structural to the house. I would therefore avoid cutting or notching into it for that reason.

 

OK. Do you have any tips to make installing a vanity easier when working with drain lines coming out of the floor like this? The vanity is a furniture style vanity. It is pretty nice. I don't want to gouge and 6" diameter hole in the bottom for the 1.5" drain pipe just because I stink at getting the alignment right.

I am all thumbs with that stuff. Sure there is a handy trick at how to get that right, easily.

 

Dry set the vanity centered left/right to where you will be placing it and push it to where it is touching the pipe. Get on your hands and knees, go under it and mark where the pipes are. Then if you can set the vanity to the side of the pipes and mark its location on how far the pipes come off the wall. Transfer those measurements to the bottom of your vanity and using a hole saw, drill out your pipes. You can then box the pipes in under so you can not see them.

 

Transferring directly from the pipes. Yes, that sounds good. Thank you.

 

Your first picture shows a de facto S-trap. S-traps are not code compliant.

Here is a code compliant way:

 

Yes, I had to do exactly the same thing in the other bathroom. That is the plan. Thanks for the reminder though!

 

May I go ahead and ask another question on the subject of vanity drains going through the floor rather than the wall?

I will be centering the vanity and sink on the wall. This will require moving the drain pipe to have it in the correct place to connect to the sink drain tail piece.

Some of you guys helped me on the other bathroom where the plumber did not install the pipe closely enough. Can you tell me the approximate location I need to have the pipe in relation to the drain tailpiece to insure I can easily connect the trap?

 

My apologies. I know what I was asking was confusing. I guess what I was asking is if there were some sort of standards regarding plumbing rough-in of a vanity that would facilitate installation later. I have since found some documentation on the subject.

I am good to go accept for a shower venting question in a separate post.