Which drain pipe to use?

[TroyS]

Hi all,

I am adding a bathroom to my basement (it is already stubbed out for a shower, toilet, and vanity).

However, where the vanity will go there are 2 DWV pipes next to each other, and I'm not sure which one I would need to drain the new sink to. Can I use either one? I'm sure there's a reason there are two and that I need to use the correct one.

Thanks for any help you can provide!

 

[Sylvan]

The one LEFT is most likely the vent

 

[Sponsor]

 

[wwhitney]

So, the left hand one is 2" up to a reducing coupling, and everything else is 1-1/2"?

Then another logical possibility is that the 2" is the intended lav drain, and all the 1-1/2" is meant for vents.

Seems like it's impossible to tell without putting a camera in the pipe. A wider shot showing the other bathroom rough-ins might help.

Cheers, Wayne

 

[Terry]

Wayne has a point. The 2" part way may be a wet vent with the lav.
And without scoping it out more, how would you know?

 

[wwhitney]

FWIW, Wisconsin has its own code and both requires all horizontal wet vents to be at least 2", like the UPC, and allows a 1-1/2" dry vent for a WC (up to 2), like the IPC.

Cheers, Wayne

 

[Helper Dave]

My guess is that the 2" is the drain. We're in WI, and plumb basement sink roughs exactly like that.

The sink wet vents the bathroom group. The other vent is usually a floor drain.

 

[Jeff H Young]

with little to go on other than a tiny pic. I am pretty sure everyone is correct and using the 2 inch side makes most sense to me