I'm certain the 3" pipe on the left is the toilet drain (it is about 12" form the wall and has a rounded cap on it). I'm guessing the shorter 2" capped pipe on the right, up against the wall, is the vanity drain. Then there is a 3.5" pipe on the bottom right that has a plug that looks like it's screwed in, but is actually not screwed in (it pops straight out). From what I understand, this is definitely not for the shower and is most likely a cleanout. Looking down it, I can see the water go by as my wife flushes the toilet up stairs. This seems like an odd place to put a cleanout, given the location of, what I believe is, the vanity drain. Also, I think the pipe that goes to the ceiling in the center of the picture is the vent stack. There appear to be larger pipes that come down the wall further to the left that I believe is the main drain that runs under this set of pipes.

Here's a photo (click for full size):

Photo of pipes

So, 3 questions:

  1. Is that 2" pipe most likely for the vanity?

  2. If so, does this mean I'll be tying in to the vertical pipe for a dry vent, although there is no roughed in horizontal pipe pointing at the 2" drain?

  3. Is that horizontal pipe pointing to the left a vent pointing to where the shower is intended to be located (as in that is the dry vent for the shower)?

1 Answer 1


A shower drain needs a trap, so check under the cap on the left to see if there's a trap or a straight drain. If it's straight, then your assumptions are likely right that it's a toilet and the other one is a clean-out (fix that cap, you don't want sewer gases getting it). If you don't have a shower drain here, then I'm guessing it's only roughed in for a half bath.

I don't imagine the 2" would be anything other than a vanity drain.

With the "vent," I'm left wondering if it's really a drain since I see a clean-out installed on it. I'd recommend tracing that line up the walls, as best you can, to verify it really is a vent.

As for where the horizontal line is going to the left, perhaps a washer dryer, or perhaps the plumber screwed up the T and it should be pointing to the right for the sink. It's hard to tell from here.

  • I cut the cap off of the 2" pipe on the right and it has water standing in the bottom, so I guess that means it has a p-trap and ergo is my shower drain. Thanks, BMitch for the suggestion of cutting off the cap and looking down the pipe. Now, a couple more questions: 4. Can I use that horizontal pipe as the drain for the vanity? 5. More importantly, what do I do with that 3.5" pipe? I'd like to have a fairly large shower, and it is right in the way. How do I confirm what it was intended for?
    – Jesser
    Nov 9, 2011 at 1:22
  • @Jesser Hmm, that 2" is awfully close to the wall to be a shower drain. Perhaps it's intended as a floor drain in case there's any flooding. That would put this back into being plumbed for a half bath. For the horizontal, I'd first verify whether it's a vent or a drain by tracking it up, or opening the cleanout and seeing if water goes down from any drains above. It might be too high to use as a vanity drain.
    – BMitch
    Nov 9, 2011 at 2:14
  • The pipe going up appears to be a vent, given that another pipe connects straight into it that is definitely a vent for a floor drain by the water heater. I think I'll end up moving the 2" pipe at least a few inches out from the wall, in order to use it as a shower drain. Thanks for your help.
    – Jesser
    Nov 10, 2011 at 2:53

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