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Thread: Please help make heads or tails of my bathroom rough in

  1. #1
    DIY Junior Member ironfist's Avatar
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    Default Please help make heads or tails of my bathroom rough in

    Hello all,

    My first post here -- hopefully first of many as I begin to finish my basement!

    The first task I will be tackling myself is the framing and, in order to do that, I need to figure out what the bathroom pipe configuration is. Long story short, I can't tell what fixture is supposed to go where. Below are two pictures. The first one is the original blueprint for the relevant part of our basement. The room on the top is a bedroom; the middle is the to-be bathroom; the bottom is storage. There are no walls between these rooms currently... the walls in the picture are indeed the only walls in real life. The second picture is my sketch of where the actual pipes are.

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    Some notes/observations:
    1. The red dashes are not real walls. They are invisible lines from the corner to the foundation wall, just used as a point of reference.
    2. All the measurements in relation to the pipes are on center (not to the edges of the pipes).
    3. The pipes obviously do not match up with the blueprint. The most obvious is that the tub would be facing the wrong way.
    4. I'm fairly certain Pipe A is the toilet drain.
    5. If Pipe A is the toilet, and I need 12" to the back wall, then that pushes the wall back into the bedroom quite a bit. Then what is Pipe B? How do I frame around that without closing off the bedroom door?
    6. One person's idea was that Pipe B was for a standup shower (not tub), given the pipe size. Then that begs the question: what is all that room for on the Pipe C side of the bathroom... and how would I frame for Pipe B?
    7. But my thought was that Pipe B was for the sink (like in the blueprint) -- but it seems too far into the bedroom. And I've been told that Pipe C would be too small for a shower?

    What do you guys make of it? Is something messed up? If so, how can I work with it without tearing up the slab?

    Many thanks
    Tom

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Pipe B is in the wall. A lav that wet vents the toilet.
    Pipe A is 13" in front of the framed wall. This is for a standard 12" rough toilet.
    Pipe C needs to be in a wall and it's for the tub drain and vent. This vent will either go through the roof, or tie in at ceiling level and revent to the toilet/Lav vent.
    The tub should drain on the inside wall, not the outside wall in a perfect world.

    We measure by interior dimension.
    It looks like you have 3" and 2" pipe there.
    Last edited by Terry; 05-21-2013 at 05:10 PM.

  3. #3
    In the Trades Tom Sawyer's Avatar
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    And.......ain't no such thing as 3 1/2 inch PVC and 2 1/2 is a special order
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  4. #4
    DIY Junior Member ironfist's Avatar
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    Quote Originally Posted by Tom Sawyer View Post
    And.......ain't no such thing as 3 1/2 inch PVC and 2 1/2 is a special order
    I just went by measuring the diameter, outside to outside. I'm not good enough to "eyeball" it. Terry Love thinks they are 3" and 2".
    Last edited by ironfist; 05-21-2013 at 06:12 PM.

  5. #5
    DIY Junior Member ironfist's Avatar
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    Terry, thanks for your insight.
    Quote Originally Posted by Terry View Post
    Pipe B is in the wall. A lav that wet vents the toilet.
    Pipe A is 13" in front of the framed wall. This is for a standard 12" rough toilet.
    That is what I originally thought, but I can't get the math to work. If A is for the toilet and needs to be 13" from the framed wall, then I think Pipe B winds up being a couple inches in front of that wall -- inside the bathroom, not inside the frame. Does it make sense for the pipe to not be in the wall itself?

    Pipe C needs to be in a wall and it's for the tub drain and vent. This vent will either go through the roof, or tie in at ceiling level and revent to the toilet/Lav vent.
    The tub should drain on the inside wall, not the outside wall in a perfect world.
    Somewhere around here I have pictures of the underground system taken during construction. I think I recall some kind of wet vent configuration going on, with everything connecting off towards the side of the house where the drains are.

    Assuming 3" pipes for A and B, and 2" for C like you said, are those the correct sizes for toilet, sink, and tub, respectively? I would have though the tub drain would have been larger and the sink drain smaller?

    The distance from C to the outside wall is 64" (center of pipe to inside of slab wall). Assuming a 5'1" rough-in for the tub (and assuming not framing on top of the slab wall), that should leave enough room for Pipe C to allow for the main trap and an overflow, correct?

    We measure by interior dimension.
    It looks like you have 3" and 2" pipe there.
    Ok, I measured the outside, thanks. That makes sense... I'm not experienced enough to "eyeball" them. They have caps on them, too.

    Thanks!
    Tom

  6. #6
    Moderator & Master Plumber hj's Avatar
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    If pipe "A" is 6" from the center of the wall and pipe "B" is 9" behind it, that is 15" and gives you 12" for the toilet and 3" from the face of the finished wall to the center, which is about normal. The 2" pipe could either be a vent for the bathtub trap, or the opening to the trap. No way to tell which without looking into the pipe. But, if it is a vent, the trap could be by the outside wall where the drawing shows it. In that case, tapping on the floor might reveal a thin layer of concrete over the trap "box".
    Licensed residential and commercial plumber

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    DIY Junior Member ironfist's Avatar
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    Quote Originally Posted by hj View Post
    If pipe "A" is 6" from the center of the wall and pipe "B" is 9" behind it, that is 15" and gives you 12" for the toilet and 3" from the face of the finished wall to the center, which is about normal.
    I think I see what you are saying. My diagram is measured from the center of the pipes to that dashed red line, not to the center of a wall.

    Assuming that the 13" spacing required for a toilet rough-in is measured from the center of the pipe to the wall, it seems like I might be ok. It is 6" from the center of Pipe A to that line, and then probably 7" from the edge of Pipe B to that line. That's 13" exactly.

    However, if the 13" spacing is measured from the edge of the pipe, then that drops down to about 11.5" - 12".

    Which is correct? Do you measure the 13" for the toilet rough-in from the center or edge of the toilet drain?

    The 2" pipe could either be a vent for the bathtub trap, or the opening to the trap. No way to tell which without looking into the pipe. But, if it is a vent, the trap could be by the outside wall where the drawing shows it. In that case, tapping on the floor might reveal a thin layer of concrete over the trap "box".
    I will see if I can find those pictures tonight and that should tell me without having to tap the concrete. I hope the trap is covered up, but I suspect that Pipe C is just a vent with no trap.

    If Pipe C is both the drain and vent for the tub -- is that big enough? 2"?

    Thanks for everyone's help!

    Tom

  8. #8
    DIY Junior Member ironfist's Avatar
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    Ok, I found the pictures of the pipe configuration before the slab was poured. Here are some...
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    I am guessing, from what I've learned here, that Pipe C is the shower drain/vent. There does not appear to be a trap there already, either on Pipe C or near the outside wall. So that means I will have to elevate the tub, correct, in order to make room for a trap?

    Does this picture confirm the wet vent configuration?

    Lastly, what is that short pipe coming out from Pipe C (that I have marked)?

    Thanks, everyone.

    Tom

  9. #9
    Moderator & Master Plumber hj's Avatar
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    YOr picture is too poor for us to tell anything about pipe "C", other than if it is connected to any of the drain lines it points to, without a turn, it is connected backwards. It "might' be a trap but again, the picture is too vague to tell for sure. Also, the "hole" had better be a sealed "ejector pump hole" and NOT a "sump pump hole". A toilet needs at least 11 1/2" so anything greater than that is "good". We usually make it 13" to allow for construction variations for the wall placement.
    Last edited by hj; 05-23-2013 at 06:33 AM.
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    Forum Admin, Expert Plumber Terry's Avatar
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    C is the vent for the tub, and the pipe extending horizontally is the trap arm before the p-trap is glued on. We always install the trap "after" the walls are up.

    Pipe B is the wet vent for toilet, and the lav is also there.

    Didn't I say all this in my first post?

  11. #11
    DIY Junior Member ironfist's Avatar
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    Quote Originally Posted by hj View Post
    YOr picture is too poor for us to tell anything about pipe "C", other than if it is connected to any of the drain lines it points to, without a turn, it is connected backwards. It "might' be a trap but again, the picture is too vague to tell for sure. Also, the "hole" had better be a sealed "ejector pump hole" and NOT a "sump pump hole". A toilet needs at least 11 1/2" so anything greater than that is "good". We usually make it 13" to allow for construction variations for the wall placement.
    As for the hole... I know nothing about pumps that go in basements. But after reading about what the difference is and seeing that the pipes all lead to the hole... yes, an ejector pump!

    I think I will be good on the toilet/wall configuration.

    Thanks for your help!

  12. #12
    DIY Junior Member ironfist's Avatar
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    Quote Originally Posted by Terry View Post
    C is the vent for the tub, and the pipe extending horizontally is the trap arm before the p-trap is glued on. We always install the trap "after" the walls are up.

    Pipe B is the wet vent for toilet, and the lav is also there.

    Didn't I say all this in my first post?
    Mostly, yes. User hj said, "The 2" pipe could either be a vent for the bathtub trap, or the opening to the trap" -- hence, the new picture which I thought might confirm what that 2" pipe is really for.

    Would you mind fleshing out the trap arm idea? My understanding -- which, being a novice, is probably wrong! -- is that if the intention of Pipe C was to be both vent and trap, then either:

    a) The trap would already be in the ground, and I would expect 2 holes near each other.
    or
    b) The trap would have to be installed above the floor which means I have to raise the tub.

    Which made me wonder what that horizontal pipe is. You said it is the trap arm... but that would make the trap arm underground, right? Dumb question, I'm sure, but how would I put a p-trap on that arm (assuming that's what it is) if it's under concrete?

    Also, could you please confirm whether a 2" drain is sufficient for a bathtub, and 3" is sufficient for toilet and sink?

    Thanks!
    Tom

  13. #13
    Forum Admin, Expert Plumber Terry's Avatar
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    Pipe C needs to be in a wall and it's for the tub drain and vent. This vent will either go through the roof, or tie in at ceiling level and revent to the toilet/Lav vent.
    "this vent" isn't clear enough?
    Last edited by Terry; 05-23-2013 at 12:18 PM.

  14. #14
    DIY Junior Member ironfist's Avatar
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    Quote Originally Posted by Terry View Post
    "this vent" isn't clear enough?
    Maybe we are talking about two different things. My last round of questions wasn't about venting. I understand the bit about Pipe C being a "tub drain and vent" as you said. My question now is about understanding the drain part of Pipe C. How does the trap for the drain attach to Pipe C? Above ground or below ground? A pictures is worth a thousand words:

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    Where is the trap in relation to the concrete slab floor, given what I have?

    Again, I am novice... I appreciate your advice but... talk... real... slow.

    Thanks
    Tom

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