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Thread: 2nd bathtub, slab construction

  1. #1

    Default 2nd bathtub, slab construction

    Greetings. First time post. Nice forum.

    I am building a 2nd bathroom in a basement. 4-inch concrete, etc. The new tub will be approximately 8 feet away from the original one. My question, hopefully a simple one:

    Can I tie into existing plumbing as shown in my drawing below? Specifically, the P-trap for the old tub is pretty deep, approximately 3 feet down. I'd like to tie into the existing drain pipe as shown and share the P-trap (red in my drawing is the planned new stuff).

    Also, I assume I need the vent pipe, or do I?
    (I believe all drain pipe is 1-1/2".)

    Thanks in advance for any help offered.


    (Note: Edited drawing 7/8/05)
    Last edited by comabereni; 07-07-2005 at 11:19 PM.

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    The above drawing looks good. (dated 7/8/2005)

    If you have two tubs, you should have a 2" waste line.
    The trap arms and trap can be 1.5"
    The vents can be 1.5"

    The fittings below ground would be wyes with 45's, or you could use a combo fitting.
    Last edited by Terry; 07-08-2005 at 11:51 AM.

  3. #3
    Plumber jimbo's Avatar
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    Default

    In your diagram, the vent is on the wrong side of the trap. I suspect your daigram just doesn't show what is really there.

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default drain

    The way you show it, the second tub would not need a vent, but since the entire installation is improper it is academic. You need at least a 1 1/2" line to the new tub, (2" would be better), with its own trap, and that line needs a vent within 42" to 60" from the trap depending on the drain's size.

  5. #5

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    Thanks all. I want to do this right. I think the 1-1/2" drain pipe from the original tub joins 2" pipe 3' down. I haven't unearthed enough of it to say for sure yet, but I'd be very surprised if it didn't. The building is about 30 years old.

    Yes, the vent pipe isn't drawn in correctly--I just know there is one for the original tub and was trying to indicate that I'd be joining into it for the new tub, unless I don't really need the vent pipe at all. Judging from the varying replies, it appears to be code but would work in reality without it.

    So, doing this right means I should drop the drain pipe from the new tub down to same 3-foot depth and do a new P-trap, then do a horizontal (1/4" slope per 1') to the main drain (downflow the original tub's P-trap) and wye into that. Also, I should add a vent within a foot or two of the new fixture and tie it into the vent on the original tub. Do I have this correct?

    (Note: I edited the original drawing to reflect my new understanding.)

    Thanks again.
    Last edited by comabereni; 07-07-2005 at 11:21 PM.

  6. #6

    Default

    Quote Originally Posted by hj
    The way you show it, the second tub would not need a vent, but since the entire installation is improper it is academic. You need at least a 1 1/2" line to the new tub, (2" would be better), with its own trap, and that line needs a vent within 42" to 60" from the trap depending on the drain's size.
    Seeing a diagram for the drain on a double sink (two drain pipes join above a single P-trap) led me to consider that these two tubs might be able to work the same way. I suppose the main difference is distance between the water basins (and volume of water being discharged).

    Thanks.

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Default drawing

    The new drawing looks good. Use 2" pipe for the drain, 1 1/2" for the vent, and put a 2" cleanout in the vent riser before reducing to 1 1/2".

  8. #8

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    Quote Originally Posted by hj
    The new drawing looks good. Use 2" pipe for the drain, 1 1/2" for the vent, and put a 2" cleanout in the vent riser before reducing to 1 1/2".
    That's how I'll do it. Thank you very much.

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