Hide trap below floor for Pedestal sink

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by gorman, Jan 7, 2008.

  1. gorman

    gorman New Member

    Messages:
    3
    I am installing a new bathroom with a pedestal sink. There is not enough room in the sink column (base) to hide the trap and AAV. My wife was hoping to just see the sink and not the plumbing. Is it possible to mount the p-trap and AAV directly below the sink in the floor? There is plenty of room to do this and still get enough slope for the drain water. Putting the drain in the wall is not an option in this case.
  2. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Licensed Grump
    The stand pipe above the trap would exceed 24"...potentially causing it to siphon..and smell.
    The correct way to pipe a pedastil is inside the wall with a stub out height at about 20-21" off finish floor.
    Not easy, but if you want it done right...thats the way.
    Also, the AAV (not legal in my state, but legal in many) should be 6" above the flood rim of the basin if possible to prevent water bringing debris into it when it drains.
  3. Redwood

    Redwood Master Plumber

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    Connecticut
    Depending on where you live it may be your only option.
  4. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Apparently I stand corrected by Redwood, in WI at least...I'm told code WI allows it.
    Further fuel for the UPC, IPC, national uniformity debate.
  5. Redwood

    Redwood Master Plumber

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    Location:
    Connecticut
    In wisconsin they have a special lite water they use when they make lite beer. It doesn't carry the same momentum through the trap so on pedestal sinks only they allow traps below the floor.:rolleyes:

    All other places I know of do not allow it!
  6. canton

    canton Plumber

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    66
    Location:
    Massachusetts
    Massachusetts

    Not allowed here.
  7. gorman

    gorman New Member

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    3
    Thanks for the timely advice! I will reposition the sink to make use of the back wall for the drain. Does it matter if it is an exterior wall for the drain? The supply lines will still come from the floor. Your help is very appreciated. This forum is the best!
  8. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    A drain in an outside wall is okay, Supplies through the floor is highly recommended. How are you venting this sink? An AAV cannot be stashed in a wall.
  9. Terry

    Terry Administrator Staff Member

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    15,124
    Location:
    Bothell, Washington
    I've put them in walls with venilated access covers. (grills)

    Or you could run a vent up to the ceiling and tie into the other plumbing vent that the other fixtures are using.
    Or if they are on the same wall, that would even be easier.

    In Washington, the drain must be in the wall too.
  10. Nate R

    Nate R New Member

    Messages:
    472
    Location:
    Milwaukee, WI
    Looked it up. Amazing that they (WI) allow this much fudge factor with a pedestal sink:

    82.32 (4)(b) b The vertical distance between the top of the fixture drain outlet of a pedestal fixture or a cuspidor and the horizontal center line of the trap outlet shall not exceed 60".

    The Wisconsin code specifies 15" as the max vertical drop for most other fixtures. (It notes exceptions.)

    If I have a 2nd floor pedestal sink, (I'm in Wisconsin) I read this as the trap could be below the floor level, or does the trap need to be accessible so it couldn't be enclosed in between floors unless there was an access panel to it?
  11. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    If you can put the trap below the floor, not allowed where I live either, but if you can then what about the AAV, would it still not have to be 6" above the flood rim. The only exception I know of for that is under sinks and they still say as high as possible. So if they allow the trap below the floor then is as high as possible under the floor, I can't see you getting two pipes up the pedestal.
  12. gorman

    gorman New Member

    Messages:
    3
    In Pennsylvania, I was told by a licensed plumber, we can put the AAV in a wall or ceiling, if there is an access panel for maintenance. I didn't ask about installing it in the floor, but based on what I have read here, it would not be a good idea. I am planning on putting the drain and AAV in a pipe chase to be built behind the sink, and with an access panel. The trap arm will extend from below the sink drain horizontally into the chase. From what I have gathered, the problem with the trap under the floor is the distance the waste travels before going into the trap. That's it, I just need a pedestal sink with a very short pedestal (LOL).
  13. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    If you live in PA as I do it is illegal to put the AAV under the floor, it is also illegal to make a stand pipe that long too for a pedisatal or anything else. Water flows the same rate down a drain as it does in the rest of the world excep where this guy lives. I was just wanting to know if they are allowed to put the trap under the floor because they can't get up the wall, then what about the AAV?
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