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Thread: Basement Bath groundwork

  1. #1
    DIY Junior Member gt2nome's Avatar
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    Default Basement Bath groundwork

    I'm building a house in VA and wanted to rough-in plumbing for a future basement bathroom. My plumbing knowledge is 1/4" per foot, it all flows downhill and vent pipes are a royal pain to figure out.

    My questions are:

    1) I have placed a 6" sleeve under the footer before it was poured, so I assume the main stack should go about 16-24 inches away from the wall, directly in front of sleeve (upstairs baths and kit. directly above)?

    2) To tie the toilet drain (4") into main stack do I use a long sweep T-Y, or a regular T?

    3) The toilet drain is only 3'6" away from main stack. Shower and sink are on either side of toilet. Should I relocate to obtain more room to place Y fittings for shower and sink? Or is there such a thing as double Y (4"x4"x2"x2")?

    This is what I have sketched out so far:

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    Thanks,

  2. #2
    DIY Junior Member jc60618's Avatar
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    Are you trying to figure out how to tie in the bathroom to the underground? Where is the upstairs bathroom in relation to the location of the soil stack? To tie in the toilet to the stack we usually use a sanitary tee with side inlets to accept the other fixtures. And yes they do make a 4x4x2x2 double wye
    Last edited by jc60618; 04-27-2010 at 02:22 PM.

  3. #3
    DIY Junior Member gt2nome's Avatar
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    Thanks jc,

    I read a few dwv books at the local library and went to work. I will attempt to attach a pdf of my plumbing layout (only doing basement rough-in for future bath addition, the rest of the house I will pay a plumber).

    Also attaching pics of what I've test-fitted so far.

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  4. #4
    DIY Junior Member jc60618's Avatar
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    The tub is not vented, the solution is to put in a sanitary or combo( depending on your local code) on its back between the wye and p trap. Also check your code to see if you are allowed to wet vent the toilet. Here in Chicago every fixture has to have its own vent and no wet vents are allowed.
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    Last edited by jc60618; 05-02-2010 at 08:06 AM.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Your tub is not vented.

  6. #6
    Master Plumber-Gas Fitter shacko's Avatar
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    Depending on you code, the UPC will not allow a double wye laying flat on a sanitary line.

  7. #7
    DIY Junior Member gt2nome's Avatar
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    Thanks for input. I will check the code regarding wet vents and the double wye on its back, then glue it all and call the inspector. I just wanted to get to the point where I could pour the slab.

    A few more questions:

    1) To fill in around the pipes should I use dirt and then the slab gravel, or just the gravel?
    2) For the tub I will build a box to allow room to work later. Should the top of box end up flush with slab, or like 1 inch below slab surface with a thin layer of concrete over it? Ideally the floor wouldn't have a square hole in it, but rather a marked area to be easily cut out later.

    Thanks again

  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
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    I'm not a big fan of the double wye that is laying flat without grade.
    Or am I happy that the vent for the toilet does not come off above the flow line.

    I would have used two wyes, one straight up for the toilet vent, and then you could have used a santee and armed over for the lav.
    The second wye could have been for the shower, and a 2x1-1/2" combo for that vent.
    A tiny bit more in fittings, and you are assured it all works fine.
    We know that you will be tying those two vents together.

    Last edited by Terry; 05-02-2010 at 06:27 PM.

  9. #9
    In the Trades Gary Swart's Avatar
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    It would appear you have dry fit all of your pipe and fittings. That is a major goof when working with PVC (also ABS) These are an interference fit which means the pipe will not bottom out in the fitting without the proper solvent (aka glue). If you try to really hammer the pipe in, you will have a very difficult time getting joints apart. If/when you do separate the joints, then apply the "glue", you will lose about 1/4" per glue joint.

  10. #10
    DIY Junior Member gt2nome's Avatar
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    Thanks Terry, so I should end up with 3 drain pipes and 2 vent pipes coming out of the concrete, right? I don't mind re-doing it with more fittings, it's cheap compared to the $2K I was qouted for having someone do it. The only doubt left in my mind is that I peeked at other new constructions at this same stage and none of them had more than 2-3 pipes coming out of the slab.

    Gary, I was aware of the PVC not going in all the way when dry, I split my chin open a few years back pulling apart some other pvc after test fitting it the way I thought it should fit. I plan on cutting exact lengths of pipe when I get it all good to go. Is there any substance (oil?) you can use to make the fittings bottom out?

    Thanks for your help.

  11. #11
    In the Trades Gary Swart's Avatar
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    No. What makes the pipe and fitting bottom out is the solvent (glue) actually melts the surfaces of the pipe and fitting which allows them to fit. Usually you need to hold the joint together for a few seconds to keep the pipe from pushing itself out. I'd suggest you cut and fit the pipe as you go, allowing for the extra distance on the inside of the fitting. When I looked at the picture of your layout, it appeared pieces were assembled but seeing no primer, I assumed the dry fit. Glad that you are on the right track. Just be sure you follow the other suggestions regarding the kind of fittings and their orientation. And, of course, get the venting right.

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