Nice site here... Solid answers...

I'm installing a wet bar to a finished basement... And a shower bathroom to existing rough-in plumbing... The bathroom is all vented to what appears to be a secondary vent that is a 2" pipe...

The wet bar will be around the corner and will be approximately a 10' run if I tap into the bathroom rough-in...

Directly behind the wet bar is a 3" stack that has a 1st floor toilet attached... And a cleanout... I believe it is not to code to tap into any stack that has a toilet upstream... Is this correct??

Can I install the 1 1/2" wet bar drain underground and 90 up into the wall cavity, keeping it lower than the wet bar trap??? And can I tap into that 3" stack with the 1st floor toilet attached??

If I take it around the corner to the bathroom rough-in it will be a 10' run... Is that too long??

Basically I want to know if I can tap that 3" stack with a 1st floor toilet attached... And if it meets code to run basement plumbing underground and 90 up into a wall cavity as long as I stay below the trap level of the wet bar... Or should it be run underground the entire way to that bathroom rough-in and tapped in underground...

.. I believe it is not to code to tap into any stack that has a toilet upstream... Is this correct??
And can I tap into that 3" stack with the 1st floor toilet attached??
I would keep the underground drainage at 2". . You may connect to that stack only if you vent the bar sink.

If I take it around the corner to the bathroom rough-in it will be a 10' run... Is that too long?? I would use a short sweep to get around the corner. Since the bar sink vent will come off the top of the san tee and revent back to a dry vent a 10' run is acceptable.

Can I install the 1 1/2" wet bar drain underground and 90 up into the wall cavity, keeping it lower than the wet bar trap?? Or should it be run underground the entire way to that bathroom rough-in and tapped in underground... You are proposing to install a "dog leg" in the bar sink drain line. I would keep the drainage underground and hold the 90's to a minimum. Good luck, Tom