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Thread: Main stack & offset walls: Run Horizontal?

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    DIY Senior Member speede541's Avatar
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    Default Main stack & offset walls: Run Horizontal?

    This is a follow-up question of sorts to something I asked the other day regarding installation of a second toilet, but is a new subject. The previous thread is here: http://www.terrylove.com/forums/show...-vent-waste-CI

    My 4" soil stack shifts approximately 16" due to the walls not being aligned. This shift occurs in a 26" dead space inside of a dropped ceiling. Due to space constraints, the plumber accomplished this by jogging the pipe at a 13 angle, which apparently was signed off by the city code inspector.

    I'll be in here connecting a Wye for an additional toilet (probably in the lower vertical section). This would be an opportune time to correct this slope, if it's wrong.

    My concern is that, at such a slope, am I up to code? Is this setting me up for a clogged waste line? I am working under the impression that anything less than 45 is no longer vertical, and that a 13 slope is well over the recommended 1/4" per foot for a horizontal run.

    However, I don't have room to run 45 in this space, due to the space taken up by the Tee connecting to the existing toilet. As I see it, I have three choices:

    1. Should I leave it as is?
    2. Should I / can I transition to horizontal for 16", then back to vertical?
    3. Should I remove the existing Tee, run the stack transition at 45, and re-connect the existing toilet using a Wye?


  2. #2
    In the Trades Wally Hays's Avatar
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    that offset would be fine
    Perception is 3/4 of reality

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    DIY Senior Member speede541's Avatar
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    Left as-is, or would you run yours horizontal or at a 45?

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    Plumber jimbo's Avatar
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    1/4" per foot is the MINUMUM slope, and although the topic is hotly debated on these forums ( wanna start a fight...ask about water outrunning the waste!!!!).......there is no MAXIMUM slope.

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    DIY Senior Member speede541's Avatar
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    Roger that, Jimbo.

    So... A "roughly horizontal" jog is OK in the main stack?

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    You are allowed to offset horizontally. But there are rules and the offset you have drawn would not violate any codes.

    An offset at 45* would not be considered a horizontal offset.

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    DIY Senior Member speede541's Avatar
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    Cool, thanks!

    What are the specifics if I wanted to turn this into a truly horizontal jog (2 90's)? If I could do that, it would certainly make connecting the second toilet an easier job.

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by speede541 View Post
    Cool, thanks!

    What are the specifics if I wanted to turn this into a truly horizontal jog (2 90's)? If I could do that, it would certainly make connecting the second toilet an easier job.
    Up here you would be allowed to go 1.5m, or about 6'.

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    DIY Senior Member speede541's Avatar
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    Ok, thanks, I'll run that by my inspector.

    Unless... well, you know -- any practical implications that would cause me to NOT want to go that route? Like increased noise from flushes?

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by speede541 View Post
    Ok, thanks, I'll run that by my inspector.

    Unless... well, you know -- any practical implications that would cause me to NOT want to go that route? Like increased noise from flushes?
    If you can go with two 45* elbows you'd be better off. If not you can go with 90* elbows a bit of insulation.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    There is a limit on the number of degree change of the pipe before a cleanout is required. So, you need to be careful about how many you have. I don't know the specifics. Keep in mind, the more angles, if something ever gets clogged, you may not be able to get a snake around the bends. And, each angle (90-degree) would slow the flow down.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member speede541's Avatar
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    I'd like to do 45 angles, but that would leave me with no space for the Tee for the existing toilet. Since that one is vented by the stack, I'd prefer to keep the Tee to avoid having to re-vent it.

    If I go with 2 90 angles, that leaves lots of room for the Tee, and I can probably slide a Wye in right underneath it for the second toilet (which will be vented separately).

    Or, I can go with approximately the existing layout, but I would have to put the Wye on the lower vertical section, and that would require some inventiveness on my part to run the second toilet wast pipe to that location.

    Here's a pic of the existing setup. The Tee receiving the existing toilet is connected to the hub, just above where the pipe disappears behind the framing at the top of the photo. You can see the lower section of pipe peeking out behind the wall to the left.



    Here are the two other options I'm looking at, if I don't stick with the existing layout.



    Lastly, here's the stack diagram if I add the two 90 angles. You can see that I have two 90's and two 45's down stream, before the cleanout. It wouldn't be too much trouble to add a cleanout on the first floor just before the lower set of turns.

    Last edited by speede541; 07-14-2010 at 10:01 AM. Reason: edit photos

  13. #13
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    The reason it goes at an angle, and I am not sure if it is really 13 degrees or not, is that someone either made a bad measurement and came up short, or they used a piece of pipe they had and did not want to insert a short piece to make it the correct size. If we were there, we could decide which, of several methods, would be the best one, and inserting a "Y" might not even be one we would consider.

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    DIY Senior Member speede541's Avatar
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    I don't know how he (the previous plumber) achieved 13, but that's what I'm seeing on my digital level.

    Well shoot, there's not as much space in here to do exactly what I want, so I'm combining options 1 & 2 from my previous drawing and doing:
    - horizontal transition with a medium sweep 90
    - Tee at the top as drawn
    - Wye in the lower wall for the 2nd toilet
    - cleanout at the base before moving into the basement

    Off to the plumbing supply with a long list. Wish me luck!

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by speede541
    Off to the plumbing supply with a long list. Wish me luck!
    Good luck!

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