Need Help with Basement Bathroom Venting/Plumbing

[Steve K]

I'm starting to plan a bathroom in my basement. When my house was built, there was some preparation for a bathroom. I can see where the toilet and shower drains are. I see two pipes coming from the floor where the sink will be. I want to understand how to determine which pipe is the sink drain and how this system could be vented. I've attached a picture.

 

[frodo]

I am going to ASSUME the pipe i drew coming from the shower is the vent

here is how you tell, cut the caps off both pipes

using your tape measure, snake it down both drains. you will be able to ''feel'' the fittings

the drain should allow you to push your tape all the way

the vent should be very/more difficult because of the connection

try it and post back

 

[frodo]

 

[Steve K]

View attachment 19823

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Thanks for the input “frodo”. I’ll try it in a few days and let you know.

 

[Steve K]

frodo - I checked the pipes per your suggestion.
The pipe on the left was fairly easy to snake the tape (9 ft), but it didn't come out at the shower drain.
The one on the right was difficult (2 ft).
I also noticed that the shower drain in the floor goes perpendicular to the way you drew it (see red line in the attached picture).
Please let me know your thoughts.

 

[frodo]

the left is the drain as you have it marked