island vent a bathtub??

Discussion in 'Shower & bathtub Forum & Blog' started by Weakenedwarrior, Apr 21, 2007.

  1. Weakenedwarrior

    Weakenedwarrior New Member

    Messages:
    9
    Hi,
    I am currently in the process of converting an old bedroom in to our new bathroom. The job has been quite the challenge. Our house was built with concrete block exterior walls. The bedroom was added on to the home after it was built, so all four walls are block. To make matters worse, there is no basement under the addition, and the floor joists are 2x8. They run in the most inconvenient direction for running drain plumbing.

    This all has caused many challenges for this particular job. Especially when it comes to running drain vents. I had to add a soffit to run some of the vent pipes, as well as fur out a section of one wall behind the shower and tub to run the main vent stack.

    Where I am getting stuck is on the bathtub vent. It is a deck mounted whirlpool type tub. The way the bathroom is being laid out is making it near impossible to put in a drain vent without boxing out a section of the wall near the tub. It will be real unsightly to do this. That wall is concrete block, and has 3/4 furring strips with 1/2 drywall attached. There is no room to run a vent behind the drywall.

    So. Can I run an island vent for a bathtub? MN does not allow an AAV. I have included these images so I don’t have to describe the current layout, or what I am intending to do. My only other option is to run the vent up at a 45 until it hits the nearest wall, and have it meet up with the vent inside the soffit. If I do that, it will have to be boxed out right there.


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  2. in your 4th photo, a red oval area is where the drain is under the floor. To avoid sending a vent up "45 degrees", that drain is supposed to head to a vent first, not to the rest of the drain system. After it turns wherever it needs to, to get vented, it connects to other drains. That is what i know or think i know about drains and vents.

    I would ask all the same questions if I were in your situation, and i would probably be planning right now to put an AAV in: after the P trap, under the floor, on a pipe that sticks straight up and comes through the floor, leaving me with an AAV inside a tub podium built to let air access to feed the AAV.

    Other people, and real plumbers, will help you more.

    David
  3. Weakenedwarrior

    Weakenedwarrior New Member

    Messages:
    9
    From what I have read, AAV are not allowed in MN. They were temporarily until 2005, but not anymore. The vent is currently before the rest of the drain system. It is after the trap, and before it hits any other junction. This is currently the only method I KNOW is per code:

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  4. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    I don't believe you mean an island vent. Island venting is for fixtures that rough in above floor level, like a sink. Tubs rough-in below floor level. From the picture it appears all you need to do is bring the vent up ito the tub enclosure then route it to the wall of the closet and up to the vent in the soffit. Use regular or long sweep elbows below the flood rim, do not use vent elbows. It would also be a good idea to put a cleanout on the vent inside the closet.
    Last edited: Apr 21, 2007
  5. Weakenedwarrior

    Weakenedwarrior New Member

    Messages:
    9
    For an Island vent to work properly, does it matter if the trap is above floor level or not? My original plan for the vent was exactly as you suggested, but code says I cannot make a horizontal vent run unless it is 6" above highest fixture water level.
    Last edited: Apr 23, 2007
  6. Terry

    Terry Administrator Staff Member

    Messages:
    14,763
    Location:
    Bothell, Washington
    I don't know about MN, but UPC would allow the vent to be below the flood level if done with waste fittings and then revented above the flood level.
    This is where you call the local inspector and ask for verification.
  7. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    the p-trap has to be below the floor, otherwise the tub will sit too high off the floor, the vent takes off the drain and runs into the tub box and up as we described earlier.
  8. markts30

    markts30 Commercial Plumber

    Messages:
    630
    Location:
    Phoenix, AZ
    I agree with Terry...
    I would take the vent off the waste bleow the floor and then run it at 1/4" grade up to where it can run in a wall then re-vent it...
    Just have to make sure you use drainage fittings below the tub's floodrim....
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