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Thread: another bathroom rough in

  1. #1

    Default another bathroom rough in

    Hi, I am trying to figure out what these pipes mean in the rough in for our basement. The 3 inch is obviously for the water closet, and the others I'm not sure. Any help? The 2 inch pipe on the left will be in the wall and 16 inches from wall behind shelves. Is the pipe coming up in the middle the vent/lav drain? I don't hear water coming down this when any of the other bathrooms are in use.

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  2. #2
    Engineer chassis's Avatar
    Join Date
    Sep 2005
    SE Pennsylvania


    Not a pro, but here's my guess.

    3" is toilet waste drain.

    Short capped pipe on left is sink/lavatory waste drain.

    Pipe in the middle is vent.

  3. #3


    I was curious to know if it doesn't look like there is a shower/tub drain roughed in. Anybody else?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    A sink drain and a toilet drain go straight down to the main sewer line - they don't have water in them normally and no trap. On the other hand, if you had a pipe in the floor for a tub or a shower, it must have the trap below it, thus, it would be in the floor. If you looked into this, unless it dried out (which is quite possible), you'd see standing water. It is not uncommon to leave a box around the drain for a tub or shower so you can get the trap centered on the thing once installed. Without being there, it is sometimes hard to tell (in fact, often hard to tell!).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Senior Member Cal's Avatar
    Join Date
    May 2005
    Northern Virginia


    Cut that shorter pipe off a few inches from the floor and pour some water down it to see if it's trapped. I think it looks like a tub rough in.

  6. #6


    Thanks, I'll try that later today.

  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Bothell, Washington
    Blog Entries


    I would think it's a half bath.

    The 2" would be the toilet vent, which is reventing at 42" on the next floor.

    The 1.5" pipe would be a lav drain, which needs to be revented over to the 2" vent.

    Unless I'm wrong, because I'm not there and I'm guessing off of a picture.


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