Is this wrong or right way to run a drain?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by stevevaiamd2006, Jun 29, 2020.

  1. stevevaiamd2006

    stevevaiamd2006 New Member

    Joined:
    Jun 29, 2020
    Location:
    Austin
    Hello,

    I installed a double sink vanity in my bathroom, but the drain pipe is in the middle. Over the weekend I ran the PVC pipe. I inserted an image of the drain.

    Can I use a P-trap on both sinks like this?

    What should I correct? How do I fix this?

    Thanks!

    [​IMG]
     
    Last edited by a moderator: Jun 29, 2020
  2. Reach4

    Reach4 Well-Known Member

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    Location:
    IL
    The flaw, at least the main flaw, is that the traps have no vents.

    Austin uses UPC. They probably allow AVCs, but maybe not. If they do, you could put a double fixture fitting where you have a tee, and put an AAV at least 4 inchs above that.

    To the left and right of the double fixture fitting, I would go to slip drain lines instead of glued, but glued is certainly good. Glued is harder. Those drains plugs at the bottom of your traps don't really contribute. To convert to slip, you would put trap adapters.

    The elbow into the wall should be a long sweep elbow. You might be able to unscrew the AAV, and put a snake down there if that elbow clogs. Awkward.

    [​IMG]

    Another possibility would be to use two Oatey 39225 in the trap arms. Probably saving that tee where your trap arms join is not going to be right, but may work OK.

    It is also possible you could use two Studor 20396, but those must be exactly in line. Odds of that fitting in with what you have are low.
     
    Last edited: Jun 29, 2020
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  4. Terry

    Terry Administrator Staff Member

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    No proper venting of the traps, you made an S trap out of it and traps will siphon.
    Wrong fittings for the drains. Those are water supply fittings, not waste fittings.
    Raising the plumbing to clear the drawers was not the right thing to do unless you add an AAV for venting.
     
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  5. stevevaiamd2006

    stevevaiamd2006 New Member

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    Should I just start over?

     
  6. Reach4

    Reach4 Well-Known Member

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    How would that work? Would you get a tool to cut out what you glued to the wall?

    Rectorseal 97402 looks very interesting. Cheaper and easier to find than the Oatey product. This device can mount an AAV.


    [​IMG]
     
  7. wwhitney

    wwhitney Active Member

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    Location:
    Berkeley, CA
    Seems reasonable to me. The conventional arrangement would be this, I think, starting at the wall and going upstream:

    Horizontal PVC DWV pipe (trap arm)-> trap adapter -> horizontal tubular pipe (trap arm) -> tubular P-trap -> vertical tubular pipe -> tubular tee with two horiziontal inlets -> tubular horizontal tailpiece (each side) -> tubular 90 elbow (each side) -> tubular vertical tailpiece (each side) -> sink basin (each side).

    Or if it fits better, you could put the P-trap under one sink, and use a 45 on the horizontal at the wall to get the trap arm pointed towards that sink. Then your tubular tee would have one inlet vertical, and only the other sink would need the horizontal tail piece.

    Cheers, Wayne
     
  8. stevevaiamd2006

    stevevaiamd2006 New Member

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    Thanks! I'll try the second option.
     
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  9. WorthFlorida

    WorthFlorida The wife is still training me.

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    It'll probably be easier to pull the vanity out and open the wall. If you have PVC pipe it be very easy to change. I had a one sink vanity and I had it changed for two drains. I had a plumber do this since I was short on time for the tiler. The home is all CPVC and he used PEX to expand it to two sets of stop valves. Drywall is easy replace with what you cut out. Taping and final finish was not needed because the entire wall would be covered up by the vanity. Here ar ebefore and after pics. The center section of the new vanity was a three draw cabinet.
    2 sink.jpg one sink.png
     
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  10. stevevaiamd2006

    stevevaiamd2006 New Member

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    It is 30 inches from the left sink tailpiece to the right sink tailpiece. Do I need an extension for the horizontal tail piece?
     
  11. wwhitney

    wwhitney Active Member

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    So, I hope someone else will comment, because I don't really know if the layout I indicated is reasonable for sinks 30" apart. It's common on double or triple bowl kitchen sinks, but those are typically closer together.

    Also, I recommend WorthFlorida's suggestion, you'd end up with a better result and it's not that hard to cut drywall.

    But assuming it's OK to have a horizontal 30" tail piece (not sure that's the right name if it's horizontal), then it seems like you'd need a slip joint extension in there, unless you can find a 30" tubular part.

    What size is the PVC at the wall?

    Cheers, Wayne
     
  12. stevevaiamd2006

    stevevaiamd2006 New Member

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    The PVC from the wall is 2 inches in diameter.

    According to Summerville-home-inspector website, that the horizontal tailpiece cannot exceed 30 inches. I am not sure how creditable that source is but it might lead me in the right direction. Does anybody else have any advice or information regarding the maximum length of the horizontal tailpiece?
     
  13. wwhitney

    wwhitney Active Member

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    Just to double check, do you mean it's 2" trade size? So the OD of the pipe is 2-3/8", and OD of a hub on a fitting is around 2-3/4"?

    Or is it 1-1/2" trade size, which means the OD of the pipe would be 1.9" and the OD of a hub on a fitting would be around 2-1/4"?

    FWIW, if you go with the central p-trap location (my first suggestion), then the horizontal pieces on each side will be only 15".

    Cheers, Wayne
     
  14. stevevaiamd2006

    stevevaiamd2006 New Member

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    Sorry, I meant 1 1/2 diameter inside.

    I rather do the second option if possible because then I do not have resize my drawers.

    Can I use kitchen slip joints on a bathroom sink? I found everything using slip joints but the end of the horizontal tailpiece has a nut on it. It is used for kitchen sink.
     
  15. wwhitney

    wwhitney Active Member

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    Looks like if you go with tubular, the tees are all 1-1/2", so you'll need to 1-1/2" from that point onward. If your sinks have the usual 1-1/4" tail pieces, you'll need to figure out where to transition on each side from 1-1/4" to 1-1/2". I don't know enough about tubular to know whether it is the case that any 1-1/2" slip joint fitting will accept a 1-1/4" x 1-1/2" reducing washer to make the transition, or if the fitting has to be specially designed to be compatible with the reducing washers for it to work.

    In case you haven't found it, this is a 1-1/2" tubular set up that works for dual sinks on up to 26" centers:

    https://www.supplyhouse.com/Sioux-Chief-230-270625104-1-1-2-x-25-Centers-with-Baffle-Tee-White

    So with an 1-1/2" extension, and a way to change the top inlets to 1-1/4", it should do what you want. Unless, of course, there's some prohibition on >26" centers that I'm unaware of.

    Cheers, Wayne
     
  16. stevevaiamd2006

    stevevaiamd2006 New Member

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    The 45 degree elbow off the wall is not angled enough. Can I use a 60 degree elbow off the wall instead?
     
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  17. wwhitney

    wwhitney Active Member

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    The P-trap gives you some flexibility because you have two joints to rotate, that's not enough to make it work?

    You also have the option to use the central tee configuration (elbows under each sink, the tee has two horizontal inlets) and just move it as far off center as you can get to with the 45 as close to the wall as you can get it. If that clear your drawers properly. That would also allow the horizontal tailpiece on each side of the tee to be a single piece.

    But if you really need more than 45 at the wall, better would be to use a 45 and a 22.5, because the radius on a 60 is smaller than either the 45 or 22.5.

    Cheers, Wayne
     
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  18. stevevaiamd2006

    stevevaiamd2006 New Member

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    Location:
    Austin
    Thanks for the reply.

    If I move the central tee off center, then the horizontal waste arm connecting to the right sink would be more than 18 inches from trap.

    I found a video on Youtube by This Old House. The show installs a double vanity on a single drain. It looks like they use a Y adapter that tees off to the trap for the left sink and branches off towards the right sink which curves around along the wall to reach the right sink. It's called "How to add a second sink to a bathroom vanity." The drain configuration looks interesting. If I could do that, then I think it'll work better. What do you think?
     
  19. stevevaiamd2006

    stevevaiamd2006 New Member

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    Jun 29, 2020
    Location:
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    I talked to my plumber. He said he can do it without resizing my drawers for $425. Is that too high? I would guess not since it is extensive and custom. It is not any normal drain configuration.
     
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