Vanity Plumbing Options

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by JD3263, Apr 22, 2013.

  1. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    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 :D
    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
    IMG00810-20130422-2225.jpg


    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.
    IMG00812-20130422-2312.jpg



    Thank you,
    Jared
  2. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
    Bothell, Washington
    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?
  3. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    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.
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
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    Location:
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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.
  5. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    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. cacher_chick

    cacher_chick Test, Don't Guess!

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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.
  7. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    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...

    IMG00815-20130424-0118.jpg
  8. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
    Bothell, Washington
    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.
  9. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    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!
  10. asktom

    asktom Member

    Messages:
    529
    Location:
    Victor, MT
    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.
  11. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
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    You would put an AAV above the double fixture cross.
    That would vent both traps.

    [​IMG]

    A double lav setup.

    [​IMG]

    A single

    [​IMG]

    A single wet venting the toilet.
    Last edited: Apr 24, 2013
  12. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    Like this, right? It would go in the red box...

    Vent.jpg
  13. cacher_chick

    cacher_chick Test, Don't Guess!

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    Location:
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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.
  14. asktom

    asktom Member

    Messages:
    529
    Location:
    Victor, MT
    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?
  15. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
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    Location:
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    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: Apr 24, 2013
  16. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    What if I used a 2" double fixture tee and used 2" pipe instead, or reduce down to 1.5" when necessary.

    How would I go about framing a wall? Would i be building a new wall in front of the block wall? Is that only done to hide the pipes in the wall?
  17. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
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    There can be no decrease in the size as it goes downstream.

    It is common to install a regular wood frame wall and wallboard on the inside of a block wall. This is how many basements are finished. It also provides a place to run electric and plumbing in the wall.
  18. JD3263

    JD3263 New Member

    Messages:
    22
    Location:
    FL
    I was at Home Depot today looking at the air admittance vents and saw these two:

    [​IMG]

    Vent 1
    Does not meet ASSE 1051 which is required to meet the Interior Plumbing code.

    [​IMG]

    or Vent 2
    Which does meet plumbing code.

    There is a pretty significant difference in price if they both accomplish the same thing; however, I don't mind paying a little extra if it's worth it. Is Vent 1 really what I'm looking for?

    Thanks again for all the help!
    Last edited by a moderator: Apr 27, 2013
  19. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
    Land of Cheese
    All I can say is when I held #1 in my hand it felt like a piece of crap, so I would buy the other one.
  20. Terry

    Terry Administrator Staff Member

    Messages:
    14,904
    Location:
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    Last edited: Apr 27, 2013
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