Hi.

I am in midst of finishing the roughed in full bath and want to put a bar sink on the wall behind the tub.
I will add pictures later- once I am able to get some good shots....

The way it was roughed in- I have the lav sink on the left, and the toilet on the right. On the opposite wall is the tub drain. Here is a mock up:

[drive.google.com]
I am assuming that the rough-in for the full bath is correct, and everything is vented properly. The solid red lines are what is there today as well as the vent stack- at least what I believe is there. I can only see the rough ins sticking out of the floor for the toilet, and the tub drain in the ground. The dashed lines are what I was planning to do. My plan is to tie the bar sink drain to the tub drain- since they share a wall. I was hoping that however the tub is vented- the bar sink would just use the same vent. But after reading many threads on here I am not so sure.
If this is not a good idea, please help me to figure out what I can do.

Thanks!

i would hope that your drawing is not representative of what you actually have. neither the tub nor the toilet are vented. your adding a bar sink to the tub drain further complicates this.

So right now there is nothing there- no tub, no toilet, no bar. It is a rough in. I have framed the bathroom walls to match my drawing. I assume that when the house builder installed the rough in- he took into account the venting of the tub and the bath. That was my assumption going in. Is there a way to verify that these are vented? It must be done under the slab- the only pipe going up near by is the vent that I have drawn to the left of the toilet. I thought it would be a wet vent for the tub/toilet and bath lav that are tied in under the floor.

Without being there we are just guessing, but there should be a vent in the wall between the sink and bathtub with those two connected to it. The toilet would go to the other vent and the lavatory tied into it above the floor.

OK.. so even if all the bath fixtures are vented or wet vented there is no legal way to tie a bar sink into the tub drain and not vent it. depending on your local code you may be able to tie into the tub drain and put an AAV for the sink drain.
you might be able to pass a sink drain right thru the open area where the tub apron is. that drain could tie into the stack right above floor level. this would not disturb the existing tub venting. then either vent the sink back across the ceiling or use an AAV.

Thanks packy. I think I follow what you are saying. I know I will have to vent the sink- either with an AAV if allowed or if not- I was thinking I could run the sink vent up the wall and then over to the existing vent stack- in the ceiling of the bathroom.
I am not sure I follow when you say that the sink drain could tie into the stack right above the floor level. The tub drain is under the floor. There is nothing above the floor, except the tub overflow.

Here is what I had done for the tub. The taped off piece was where the sink drain is going to go. Both would have their own p-traps.
Picture1: [drive.google.com]
Picture2: [drive.google.com]
Video1: [drive.google.com]



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Your pictures have restricted access.

just fixed access to pics- sorry about that.

you have made a full "S" trap under the tub. that is an illegal set up and is subject to syphonage. also the sanitary tee laying on its back can not be used for a sink drain.

Thanks for all the info! I think it is time to hire a pro. There seems to be too many variables and too many things that can go wrong.



Edited 1 times.