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Thread: Venting Question

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  1. #1

    Question Venting Question

    I am remodeling our 2nd floor bathroom. I have a permit so work will be inspected. I have all drain lines planned out and am happy with the layout. The 3" vertical drain line in the wall of the bathroom is part of the old work and cannot be moved or accessed (including the 90 long run at the top of the vertical drain). It will serve as the main drain for the water closet, shower and tub.

    Notes:
    1. The lavs are connected to another branch with its own venting so they are ommitted from this layout.
    2. All 90's in the layout are long run 90's.
    3. I am under the IPC and local code does not modify the IPC materially w/r/t venting.
    4. Assume the drain layout is fixed, please.


    Fixtures:
    WC - 1.6 gpf (2 dfu's)
    SH - 11.6 gpm (1.6 gpm shower head and 4, 2.5 gpm body sprays) (3 dfu's)
    BT - (2 dfu's)

    I have come to the conclusion that I have to vent each fixture independently based on my drain layout. I decided this because of the following:

    1. I cannot use the 2" vent off the WC to wet vent the shower and tub.
    2. If use a wet vent to vent both the shower and tub, I would have to go up to a 3" vent (because I'd be wet venting a total of 5 dfu's). The wall is 2x4, and I cannot run a 3" vent in a 2" wall.
    3. I cannot tie the tub into the dry vent for the KS and DW because then the KS would be wet vented which I believe is not to code. Also, the DW is 2 dfu's and the KS is 2 dfu's, so the 2" vent would have to be upsized to a 3".

    I am ok with venting like this, but I'm looking for suggestions two things:

    1. Alternate venting solutions
    2. Advice on how to tie the vents in once I'm in the attic (or can I tie some of them in 6" above the flood level of the tub?

    Thank you.
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    Last edited by dabensys; 07-24-2009 at 08:56 AM. Reason: Updated picture.

  2. #2
    Master Plumber nhmaster's Avatar
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    Default

    Vents can not run horizontal for any distance until they have been piped vertical to a point 6" above the flood level rim of the highest fixture served so none of your vents will meet code.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default vents

    None of your vents would pass the way you show them. And, if we were there, I am sure there would be much better ways to run the drains and vents. That shower drain making almost a complete circle would be a disaster. What is on the first floor? Specifically, is it the vent for the lower level bathroom?

  4. #4

    Question

    Quote Originally Posted by hj View Post
    None of your vents would pass the way you show them. And, if we were there, I am sure there would be much better ways to run the drains and vents. That shower drain making almost a complete circle would be a disaster. What is on the first floor? Specifically, is it the vent for the lower level bathroom?
    Thanks for your reply I appreciate the information on the vents not being legal. The kitchen is just below the master bath. You can see the sink and dishwasher in my drawing.

    More info to help explain the layout:

    The 3" drain that I am tying into is part of the old work. The center line of the drain, just before it turns vertical and goes down the wall is only 3" off the drywall for the 1st floor ceiling. I cannot access the 3" drain to raise it up because there is no access to it on the first floor (new Kitchen) nor the basement (new game room).

    I am using a 2" trap for the shower drain (b/c of the fact that the shower system is rated at 11.5 GPM, and the IPC calls for a 2" trap in this case. The center line on the output side of the trap, when resting on the drywall, is 6+". Thus I have a 3+" drop between the shower and the 3" drain. At a 1/4" per foot slope, that's a run of over 12 feet. This is why I've got the shower drain going in a circle. My total length is actually only a little over 7' 6', but that still puts the slope between 1/4" and 1/2". I'd love to just run the shower trap straight into a wye on the 2" section that runs into the 3" drain but the slope would end up being way too steep.

    Regarding the venting, if I were able to convince my wife to allow me to drop some of our new kitchen cabinets and cut into the wall to gain access to the 3" drain, AND if I could remove the 90 elbow and extend the 3" drain pipe up into the attic and through the roof, would that vent then satisfy IPC requirements? This would also allow me to remove the shower circle drain and run it more directly.

    BTW...I got the idea for venting from the original layout of the bathroom, which had a 2" vent running horizontally for 2' from the wall and wying into the WC. I assumed this work was acceptable as the work was done when the house was built in 1985.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default Dwv

    WHY do you have a 3" pipe running where it does? Normally it would only be there if it had to be, and the usual reason for "having to be" is that it is connected to another bathroom, and if so your ENTIRE drawing is wrong. As for the shower, you are going at it backwards. You DO NOT figure out how long a pipe has to be to "use up" the available pitch and then decide how to run that much pipe. You run the pipe the shortest distance and use as much pitch as necessary or all that you have, as long as it is AT LEAST/MINIMUM 1/4" per foot.

  6. #6

    Question dwv

    Quote Originally Posted by hj View Post
    WHY do you have a 3" pipe running where it does? Normally it would only be there if it had to be, and the usual reason for "having to be" is that it is connected to another bathroom, and if so your ENTIRE drawing is wrong. As for the shower, you are going at it backwards. You DO NOT figure out how long a pipe has to be to "use up" the available pitch and then decide how to run that much pipe. You run the pipe the shortest distance and use as much pitch as necessary or all that you have, as long as it is AT LEAST/MINIMUM 1/4" per foot.
    Good morning. Thanks for the response. I cannot tell you why the plumbers who worked on this house back in 1985 ran the 3" line from the second floor bath to the building drain, but they did. And I know that it does not serve any other fixtures on the second floor, first floor or basement because I've seen the plumbing in both walls when we had the kitchen and game rooms renovated. So, the drawing is accurate... I won't comment on it being *right*...that's why I'm posting my questions here on this forum because I do want things to be right, safe for me and my family and last for years.

    Regarding the pitch...thank you for the clarification. I received advice some time back on the proper pitch for a drain pipe and was told that an inspector may fail a layout that has too steep of a pitch. I incorrectly translated that to mean that I had to abide by the minimum pitch requirements. The 2009 IPC code book does not specify a maximum pitch (only that it is uniform). Based on your extensive experience, what do you consider 'too steep' of a pitch for a shower or tub?

    For further consideration, I am attaching 2 new, scale drawings showing only the existing work and the rough in locations for the WC, SH and BT. I apologize that they are not iso-drawings, but I wanted to show what I'm working with, with regard to the floor joists. To get a complete picture, line these drawings up side by side.

    Again, thank you for your time and attention.
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  7. #7

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    Quote Originally Posted by nhmaster View Post
    HJ you are a man of great patience.
    You are a plumbing instructor, correct?

    I am an eager learner who wants to do things right. When I read a comment like this it only tends to demean me and make me feel stupid, and I hope that was not your intention.

    I know that DIYers are the bane of existence to plumbing professionals b/c we take work away from them and we usually do things wrong, causing more problems in the end. But I am trying my hardest to do things right.

    All I ask for is your support in accomplishing that. My wife and I simply cannot afford to contract everything out on this job and she's been waiting for years for a new bathroom. This is my gift to her.

    You will find I'm a quick learner.

    Thank you for your patience.
    Last edited by dabensys; 07-25-2009 at 07:49 AM. Reason: Counted to 10... :)

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