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Thread: Venting Question

  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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    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... :)

  8. #8
    DIY Senior Member TedL's Avatar
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    Dabensys:

    You may be a quick learner, but you also seem to be a one who wants everything served up to you, with little effort on your part. Or, you think plumbing is so simple, anyone can learn with a 15 minute lesson.

    Specifically: If you spent any time reading previous postings here, or with a decent plumbing book, you would have known that the 1/4 in pitch was a min, not a fixed requirement. So, you come and essentially ask "Somebody take the time to give me a class on basic plumbing. And don't expect me to waste my time reading anything that's already been written." I agree with the patience remark.

    I'm a DIYr myself, and I've asked a lot of questions, but I try to respect the helpers' time by doing some homework first.

    BTW, if your demonstrated skills are such that your wife doesn't trust you to R&R a few screws to expose the wall behind a cabinet, you should step back and reasses whether your skills are up to handling plumbing work. There are a lot of fundamentals that go into every step (sweating a fitting or selecting fittings for and s/w a DWV connection) that nobody will (or s/b expected to) detail out for you. And then there's DWV layout.

  9. #9
    DIY Senior Member seaofnames's Avatar
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    You dont want too much pitch especially for toilets because the liquids will 'run' away from the solids leaving the solids to dry up and harden, causing a blockage in the pipe.

    There are two other reasons you dont run a lot of pitch. Joist space and if your pipe distance is very long, you can siphon the trap from the fixture you are draining.

    Use the least amount of pipe possible with the correct pitch and venting and its easy. If you take pictures or have a city inspector come over, I'm sure they can give you some good advice on how to run things. Hell, even call a plumber and pay him for an hour to design it for you if you want to do the work.

  10. #10

    Angry

    Quote Originally Posted by TedL View Post
    Dabensys:

    You may be a quick learner, but you also seem to be a one who wants everything served up to you, with little effort on your part. Or, you think plumbing is so simple, anyone can learn with a 15 minute lesson.

    Specifically: If you spent any time reading previous postings here, or with a decent plumbing book, you would have known that the 1/4 in pitch was a min, not a fixed requirement. So, you come and essentially ask "Somebody take the time to give me a class on basic plumbing. And don't expect me to waste my time reading anything that's already been written." I agree with the patience remark.

    I'm a DIYr myself, and I've asked a lot of questions, but I try to respect the helpers' time by doing some homework first.

    BTW, if your demonstrated skills are such that your wife doesn't trust you to R&R a few screws to expose the wall behind a cabinet, you should step back and reasses whether your skills are up to handling plumbing work. There are a lot of fundamentals that go into every step (sweating a fitting or selecting fittings for and s/w a DWV connection) that nobody will (or s/b expected to) detail out for you. And then there's DWV layout.
    Ted.

    Thanks for the reply. I already admitted my mistake in assuming the 1/4" minimum was an absolute, but am I not allowed to make mistakes?

    I did not just wake up this morning and decide, 'Hey, I'll see if the professionals will give me all of the answers!'. I came to this forum only after spending the last 2 months reading through the 3 different plumbing books, including the 2009 IPC code book and then making a design based in part on how the original layout was done. I assumed that the original layout was 'correct', but now I question that.

    I do respect the time of the contributors and I am not looking for it handed to me on a silver platter. And as for my skills, I grew up helping my uncle who is a carpenter do general framing and roofing jobs for 5 summers, so I'm not a novice DIY'er. And, I've already done all of the outer wall framing (adding a new picture window) and run all of the supply lines in the bathroom in question. Those things are 'easy' for me, because I've done them before, several times. However, I have never run dwv, and I do not want to do it wrong.

    That's why I bought the books and spent many hours studying. However, UI am smart enough to know that reading a book is not a substitute for practical experience or knowledge from an experienced resource. Hence, I'm here trying to get advice. Unfortunately, I'm spending most of my time in this forum defending my right to be here at all.

  11. #11

    Talking

    Quote Originally Posted by seaofnames View Post
    You dont want too much pitch especially for toilets because the liquids will 'run' away from the solids leaving the solids to dry up and harden, causing a blockage in the pipe.

    There are two other reasons you dont run a lot of pitch. Joist space and if your pipe distance is very long, you can siphon the trap from the fixture you are draining.

    Use the least amount of pipe possible with the correct pitch and venting and its easy. If you take pictures or have a city inspector come over, I'm sure they can give you some good advice on how to run things. Hell, even call a plumber and pay him for an hour to design it for you if you want to do the work.
    Thanks for the reply 'sea of names'...interesting handle btw.

    I took HJ's advice and am in the process of rerouting the shower and tub drain layouts, sending them straight back to the wall where I can then drop them into the 1st floor wall and tie them in to the 3" that is already there. At the wall, I'll vent the fixtures individually and tie them together in the attic. That should correct all of the issues pointed out so far.

    Call me henpecked, but my wife is going to kill me. We just spent nearly $20k having new cabinets, counter tops and a custom backsplash put in, and by all looks of it, I'll have to bust out some of the backsplash (in addition to removing the upper cabinet) to gain enough access to the wall cavity to run the new drain.

    Oh well, what can you do...

    Thanks for giving me advice instead of a sermon!

  12. #12
    DIY Senior Member TedL's Avatar
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    You and your wife and family are the ones who will have to live with the results of your efforts. A well functioning indoor plumbing system is a wonderful thing that you can pretty much forget about. A poorly done one can make daily living annoying or even unsafe.

    You have dismissed as "too costly" hiring a plumber to do even the planning. The best advice you received was to have a plumber in the room do the layout, (even if you do the actual work), but you dismissed that out of hand.

    If you can get your inspector to discuss your plans (in detail) in advance, that's about as good as you can possibly get with your approach.

    If you can't get the inspector to talk to you about your plans before you start, you probably are dealing with someone who is at best busy and impatient; at worst, a hard-ass sob who doesn't like DIY plumbers. You will most likely regret plunging ahead on your own design when you have to rework it after it's installed, say, because you used the wrong (or no) primer.

    It's always least expensive to make sure you do it right the first time.

    Good luck. And remember that the advice that's often most valuable is that which does not agree with what you already know or wish to do.

  13. #13

    Default

    Quote Originally Posted by TedL View Post
    You and your wife and family are the ones who will have to live with the results of your efforts. A well functioning indoor plumbing system is a wonderful thing that you can pretty much forget about. A poorly done one can make daily living annoying or even unsafe.

    You have dismissed as "too costly" hiring a plumber to do even the planning. The best advice you received was to have a plumber in the room do the layout, (even if you do the actual work), but you dismissed that out of hand.

    If you can get your inspector to discuss your plans (in detail) in advance, that's about as good as you can possibly get with your approach.

    If you can't get the inspector to talk to you about your plans before you start, you probably are dealing with someone who is at best busy and impatient; at worst, a hard-ass sob who doesn't like DIY plumbers. You will most likely regret plunging ahead on your own design when you have to rework it after it's installed, say, because you used the wrong (or no) primer.

    It's always least expensive to make sure you do it right the first time.

    Good luck. And remember that the advice that's often most valuable is that which does not agree with what you already know or wish to do.
    Thanks for the advice Ted.

    Something I guess I haven't made clear is that, other than the demo, I have not and do not plan to do any new DVW work until I show the inspector my design and get his approval. I've talked to him once and he 'seems' like a nice person, but busy like you said. All the work I'm doing relating to the DWV is on paper right now.

    You know, one problem with this type of communication method is that you all can't read my mind, nor can I read yours. Ommitted information can quickly lead to misunderstanding, which I believe has partly happened here.

    I'll stop posting to this thread and only repost to a new thread if I have specific questions. Thanks again.

    PS: How did you go about doing your first DWV layout?

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Default vents

    You asked what is "too much" pitch. The answer is there is none. Vertical pipes have "infinite" pitch and they work quite well. The only requirement is that they have at least the minimum pitch. There is an interdepence between the pitch, the length of the drain line to the vent, and the size of the pipe which can restrict you from having excess pitch, but it a restriction caused by math and physics, not flow.

    As for the
    "You dont want too much pitch especially for toilets because the liquids will 'run' away from the solids leaving the solids to dry up and harden, causing a blockage in the pipe",

    comment, it has been debunked by MANY testing lab and university studies.
    Last edited by hj; 07-25-2009 at 02:05 PM.

  15. #15

    Smile pitch question

    Quote Originally Posted by hj View Post
    You asked what is "too much" pitch. The answer is there is none. Vertical pipes have "infinite" pitch and they work quite well. The only requirement is that they have at least the minimum pitch. There is an interdepence between the pitch, the length of the drain line to the vent, and the size of the pipe which can restrict you from having excess pitch, but it a restriction caused by math and physics, not flow.

    As for the
    "You dont want too much pitch especially for toilets because the liquids will 'run' away from the solids leaving the solids to dry up and harden, causing a blockage in the pipe",

    comment, it has been debunked by MANY testing lab and university studies.
    Thanks HJ! I appreciate the feedback. I have heard many times the story that too much pitch will 'leave the poo behind'. If you have any links to info on the any of the studies, please post them, I'd be interested in reading them.

    Also, I want to thank you for all your posts, to me and others. I often see you answering many questions every day, and I know it takes a lot of your time. As a novice w/r/t plumbing, I appreciate that you are willing to deal with my (on many occasions) stupid questions/mistakes. So long as you don't mind answering them, I'll keep asking.

    Thanks again.

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