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Thread: Vanity Plumbing Options

  1. #1
    DIY Junior Member JD3263's Avatar
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    Default Vanity Plumbing Options

    Hello,

    I'm trying to determine the best option I have for plumbing our vanity. There was initially only one sink, but we're installing two now. I intend on using a splitter for the water lines to both sinks and having the drains from the sinks lead to the single pipe in the wall. I drew a couple sketches of options I was thinking about, but one has somewhat of an S I think...

    Which would be the best option? Or is there another possibility? Also, please explain "why", as I'd like to learn as much as possible. These are not exactly drawn to scale
    The distance from the farthest sink to the pipe in the wall is approximately 48 inches, of which I would decline no more than 1/4" per foot.

    Option 1:
    The distance
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    Option 2:
    This option would have one P-trap directly attached to the wall. Both sinks would eventually connect to a drain tee leading to the P-trap.
    Name:  IMG00812-20130422-2312.jpg
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    Thank you,
    Jared

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    The trap arm nust be vented within 42" on 1.5" pipe, and not below the trap arm. If you put a bend in there, it becomes an S trap that siphons the trap dry.

    I believe that 30" is the max you can go with an arm to the second bowl.

    You also have way too many bends there. Have you considered pulling drywall off and putting real plumbing in the wall?

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    DIY Junior Member JD3263's Avatar
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    That wall is an exterior block wall, so I think I'm stuck with what is there, right?
    So, Option 1 is definitely out because of the S trap. I'm not sure where else to go from here. Aside from the distance issue in Option 2, does that seem like a viable option?

    Thanks for your help.

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    Test, Don't Guess! cacher_chick's Avatar
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    You must have a vent, or the sewer gas is going to come back up the drain when the trap siphons.
    If the drain needs to be moved, move it. It might not be as easy as you had hoped it would be, but doing it right will be worth it when it is finished.

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    DIY Junior Member JD3263's Avatar
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    So, if I have a single P trap like in Option 2, would I put the vent directly above the Drain Tee that connects both sinks to it?
    If I were to move the drain, what would something like that typically involve? I understand it's tough to say without seeing it...

    Thank you.

  6. #6
    Test, Don't Guess! cacher_chick's Avatar
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    The vent must rise off the trap arm before or at the point the drain turns downward. This is often done with a sanitary tee if it is a vertical branch drain. The best way to install the drain depends on what is there to connect it to.

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    DIY Junior Member JD3263's Avatar
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    What if I did something like in the image below? Would it still be necessary to have a vent since neither arm is that long? Each sink would have its own P trap.

    If I still need a vent, can I use this connected to the double wye where the two P trap arms meet? Home Depot
    Also, how high does the vent need to be if i attach it to the double wye? I likely won't have too much room to raise it very high so...

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  8. #8
    Forum Admin, Expert Plumber Terry's Avatar
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    Every trap needs a vent.
    If you use an AAV for venting, it would be "above" the trap arms.
    What you are considering "short" is what we call within legal distance, with a vent.

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    DIY Junior Member JD3263's Avatar
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    Thank you for all the responses. I really appreciate the help!

    So, just to clarify, I should not put an AAV on the double wye. Rather, I should have an AAV directly after each P trap. Wouldn't that sort of be the same thing since the double wye is also after each P trap?

    Thanks again!

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    DIY Senior Member asktom's Avatar
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    You should only use one trap, after the two lines hook together. From the way your drawing looks, you could do it and not need an AAV.

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    Forum Admin, Expert Plumber Terry's Avatar
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    You would put an AAV above the double fixture cross.
    That would vent both traps.



    A double lav setup.



    A single



    A single wet venting the toilet.
    Last edited by Terry; 04-24-2013 at 09:20 AM.

  12. #12
    DIY Junior Member JD3263's Avatar
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    Like this, right? It would go in the red box...

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    Test, Don't Guess! cacher_chick's Avatar
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    Don't use a "double wye", use a double fixture fitting. DO put the vent valve up as high as possible, because any backup or splashing into the vent valve will cause it to fail.

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    DIY Senior Member asktom's Avatar
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    There is no 1 1/2" double fixture tee, it would have a 2" outlet. A double wye could make the traps syphon, so that leaves a double san tee. Not the ideal fitting, but for two lavs not so horrible. Maybe I am missing something, but why not tie the drains together and drop into one trap?

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    Test, Don't Guess! cacher_chick's Avatar
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    Quote Originally Posted by asktom View Post
    There is no 1 1/2" double fixture tee, it would have a 2" outlet. A double wye could make the traps syphon, so that leaves a double san tee. Not the ideal fitting, but for two lavs not so horrible. Maybe I am missing something, but why not tie the drains together and drop into one trap?
    I agree. He said the pipe was going into a block wall, so I assumed the drain is going below grade, and should be 2".

    If it were my project I would be framing a wall to do the plumbing & electric right, but it's not my project.
    Last edited by cacher_chick; 04-24-2013 at 12:56 PM.

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