Single sink drain hookup with dual connections below floor.

Contractors plumber who is now out of the picture left me a different and unknown setup. I believe one connection is for drainage and the other is for venting. Not sure how to best hook up to single hole sink.

Main floor kitchen


Below floor in basement




Thanks in advance.

 

Strange. What is that plastic tube doing? It looks like it is hooked to the output of the trap. RO units etc would go to the upstream side of a trap via an air gap.

Only one pipe has a p-trap shown, so the sink would go there if that is the only trap. However there may be a trap not shown, so you would need to figure that out. If that is a vent line as you suspect, the vent line is flawed I think; should have hooked in within 45 degrees of vertical, but may be that is OK. I guess they expected to vent with an AAV under the sink. Will you keep access to the backside? The AAV input could be redone I think. Are AAVs permitted where you are?

Below floor... I think Canada allows traps under the floor.

 

Could the plastic tubing be for an ice maker or water supply to a refrigerator? (future)

 

I ran the 1/4 line beside the drain hole. My R.O. system resides just below in basement. I live in Ontario Canada and was able to find the following.

“Article 7.5.9.2, which covers AAVs states that, "air admittance valves shall only be used to vent fixtures in buildings undergoing renovation, and installations where connection to a vent may not be practical".

This is a main floor renovation with kitchen being moved from original location.

 

looks like the one with trap hooks to sink, the other planned for AAV. But the wye should have been rolled up on 45. Same as Reach 4 said.
There you go Rob Pin You have the code , Its one that has some discretion of inspector but go with that if he asks why your putting an aav.

 

Thanks gents, 45 degree of vertical seems logical and may have to correct this. Will drain to P-trap and add AAV Oatey or Studor depending what I can find today.