Hi all,

I'm finishing a basement and am adding an extra sink to service a small kitchenette in a theater room. I have a few drain options. It turns out it is on the wall exactly opposite the bathroom tub, so I could tie in to the pipe between the tub overflow and the tub bottom drain (with a vent at the sink trap to avoid double trapping). Other option is I could tie into a drain stack that is draining the laundry. Tie in would be a few inches above the cleanout. Those are the two most direct drain options and both are within feet of the sink. Anything I need to consider in deciding which option is optimal--or do neither work and I need a third?



Edited 1 times.

you need a third option.

Any particular reason those options don't work? A third would be to route over to the existing bathroom sink drain--that would involve two 90 degree turns and a total of about 30 feet. It's doable though if the first two are no-no's. Fourth option would be to break into the cement floor, though I would prefer not to do that unless necessary.



Edited 1 times.

can you get to this bathroom sink vent that you mention?
if you can, I don't see anything wrong with using the laundry drain as long as you vent the new sink into a proper vent stack.

Yeah, I would add a vent for the new sink. I should be able to tie in to the basement bathroom vent stack without too much trouble--it's nearby and exposed. (Or my jurisdiction does allow Studors, so I could use that as a last resort if for some reason I cannot tie into the existing vent.)

Just want to make sure there are no problems with tying into a drain stack for upper floor waste, either with code or otherwise. (As I would really love to not have to cut into the floor for this particular job...!)

I would not use an AAV if you tie a lower floor sink into a an upper floor stack.
an AAV will not compensate for the positive pressure created by the upper floor washing machine draining. a real live vent pipe will give the positive pressure a place to go.

Roger that. No AAV in this situation makes sense. While I'm at it, a closer inspection of the laundry stack revealed the following:

[postimg.cc]

The trap on the left is for the washing machine, so the branch at the top of the picture must be the vent, right? In which case, can I tie the sink vent in here somehow as well? It's much closer and easy to access than the bathroom vent.



Edited 1 times.

you can tie into it but you must tie in 6 inches higher than the flood rim of the washing machine.

If you somehow successfully tie it into the tub overflow pipe, make sure you take a photo and share it here!

I actually saw om a forum somewhere where some guy claimed to do just that. That's where I got the idea. Based on the response here... definitely *not* going that direction!