View Full Version : Bathroom remodel, drain/vent questions

07-02-2012, 10:27 PM
Hi Guys

This is a great forum! I'm remodeling my bathroom which includes moving the sink location. You can see where it was from the drain in the below picture, I'm moving it to against the wall that the broom and ladder is covering. Under the bathroom is the garage with no ceiling so I have easy access to all the plumbing (see other picture, sink drain/vent is the one on he right coming across to join the run to the main stack).

My question is can I bring the new drain for the sink directly through the subfloor and connect to the existing sink drain/vent line? Was planning on cutting the galvanized pipe and splicing in with an abs Y and ferncos.

Also, what's the best way to try and cap/plug where the old sink tied into the vent/drain line?

Thanks in advance for any help!

07-05-2012, 09:18 AM
I'm going for this today, so any advice welcome :)

I know the air has to stay behind water but as long as I connect the new sink into the old line with a y fitting I think it should do that right? Length of drain run is a concern - it will be a 2' vertical run (through the floor) then a 3' sloped run to the existing where it will tie in with a y.


Chad Schloss
07-05-2012, 09:35 AM
i'm not a plumber, but it looks like you are going to remove the vent, for the sink, and that is not allowed. when you flush the toilet, it can siphon the sink trap, and you don't want that.

07-05-2012, 09:51 AM
No, keeping the vent, just just planning on bringing the drain into it further down the run.

07-05-2012, 09:56 AM
The vent needs to come from the top of the vertical santee.
The vent can not be lower then the p-trap.


Chad Schloss
07-05-2012, 09:56 AM
you don't show a vent in your diagram. that vent that was there will now be for the toilet only. the sink can't just drop into that line without a vent of it's own. it needs to be either run straight up and joined in the attic with the existing or tied in (I think 6") above the flood rim of the sink into the existing vent.

07-05-2012, 10:41 AM
Thanks Guys! my diagram wasn't very clear. Every fixture in the house has its own vent going through the roof (they don't tie together so I have lots of holes in the roof!). The current bathroom sink tees within the wall into the drain which goes up to though the roof to vent and then down through the floor where it runs horizontal (with the correct pitch) into the main drain line.

I need to move the bathroom sink and I want to make use of the existing drain/vent line. I can't tie the drain into the stack within the bathroom becuase I'd have to go through all the studs in a load bearing wall. My idea is to take the drain through the floor and then tie in to the horizontal part of the existing line (so basically a few feet further down the line from where the curent sink tees in).

07-05-2012, 10:47 AM
So in my diagram above looks like the vent would tie in below the p-trap, which as Terry said I'm not allowed to do right? So can I tee the drain within the wall, run down into existing drain AND run up to existing vent. See below...

07-05-2012, 11:54 AM
So can I tee the drain within the wall, run down into existing drain AND run up to existing vent. See below...

Yes. Something like that.