Lateral transitions in vent stack

Discussion in 'Remodel Forum & Blog' started by Texas_RSA, Mar 22, 2021.

  1. Texas_RSA

    Texas_RSA New Member

    Joined:
    Mar 22, 2021
    Location:
    Houston
    I have some a question on plumbing code relating to a vent stack modification in a shower/bathroom remodel on the ground floor of a Texas home (cement slab, no basement, pictures attached).

    This remodel will convert what was a small (and badly leaking) shower (3'x3') to a larger, walk-in one, move the shower drain to the center of the larger area (3'x6'), and relocate the h/c water lines and shower assembly to a rebuilt near wall on the other side of the shower.

    To summarize what I've done so far:

    The original framing enclosed the vent stack in a wall recess between the shower and the garage. I've replaced this framing, and used the recess to expand the shower area (pictures 1, 2, and 3):

    p1.jpg
    p2.jpg

    p3.jpg

    I've built new framing to contain all the new shower plumbing as well as the vent stack that serves the toilet. I removed the original near wall and rebuilt it using 2x8 lumber so that I could fit 3 inch PVC (3.5 inch OD, 4.0 inch OD at flanges) without violating any building codes (4.0/7.25 < 60% stud width), and to avoid any interference between the vent stack flanges with backerboard, sheetrock, etc. I also changed the path of the vent stack with two 90 degree bends to keep the PVC and clean-out access close to the garage wall, and to keep it from interfering with the shower valve rough-out and water lines (pictures 4 and 5):

    p4.jpg

    p5.jpg

    My questions:
    1. Does this dogleg (pictures 4 and 5) at the clean out put me in violation of any plumbing codes? I've read elsewhere that there is a minimum height (6 inches?) for lateral transitions above any overflow associated with the waste line being vented, and transitions below this minimum need to be made via 45 degree bends at most. The vent stack line immediately serves the sewer line from the toilet. Should I reroute these elbows farther up in the wall?
    2. Does anyone see a problem with with framing itself -- two neighboring 2x8 studs penetrated by 4 inch diameter holes?

    Sorry for the lengthy post, hoping someone has seen this sort of thing before. Thanks in advance.
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Houston is under UPC. https://www.houstonpermittingcenter.org/help/codes

    1. EDIT: I see this is vent-only, so that santee is very probably OK with UPC. img_2.jpg was drawn with drainage in mind, but it would make for easier snaking.

    2. Your cleanout may or may not be impossible to use IMO. What will the panel give access to-- both the hole and the cap? Why not extend the pipe thru the hole into the garage before putting the cleanout cap?
     

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    Last edited: Mar 22, 2021
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  4. wwhitney

    wwhitney Well-Known Member

    Joined:
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    Location:
    Berkeley, CA
    1) It would be helpful to know what the below slab layout of the drains and vent takeoffs is. If the vent riser is connected to the WC fixture drain as a dry vent, then yes the dog leg should be at least 6" above the WC flood rim level. On the other hand, if the vent take off is for the shower trap arm, and the shower is wet venting the WC, then your horizontal segment would only have to be 6" above the shower curb. Presumably you are going to be opening up the slab to move the shower drain, so you'll gain some insight at that time.

    If you decide to adjust it, you obviously could move your quarter bend/san-tee on its back configuration up. Another option is to replace it with a 45 and a wye, and then your cleanout would be pointing up at a 45 degree angle. That configuration is never horizontal, so the height is not limited. Not sure how you are going to be accessing the cleanout, if that would work.

    2) Not entirely sure what the OD is on a 3" Schedule 40 plastic hub, but I think it's close to 4". So if your lumber is green (wet), and you have a fitting hub inside a 4" hole, there's a risk that as the wood dries, the hole shrinks and it clamps around the plastic. Leading either to unnecessary force on the plastic or the wood splitting.

    Another option with a 2x8 plate is to use two 2x4s flatwise studs on either side of the plumbing, with some bridging between them maybe 24" o.c. vertically.

    Cheers, Wayne
     
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  5. Texas_RSA

    Texas_RSA New Member

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    Mar 22, 2021
    Location:
    Houston
    Reach - thanks for the answers, pic. As assembled, the socket of the clean-out came through the stud and the plug was removable. But I will redo the stud around the clean-out (was trying to keep the fixture from sticking out into the garage bay, but there may be no way to avoid this). I used a santee as this was the original configuration -- except without the lateral transition.
     
  6. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Is this vent for the shower? You may have been just fine with no changes. These are 1-1/2 inch pipes?

    Is this wall at right angles to the garage wall? You could use a flush cleanout with a flush plug in the garage, and with more wood around the cleanout, have a big-enough hole. With your cleanout, if you ever had to use it, I would worry about smelly stuff falling in the stud space during cleanout.
    [​IMG]
     
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  7. Texas_RSA

    Texas_RSA New Member

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    Mar 22, 2021
    Location:
    Houston
    Wayne thanks for the speedy reply. Yes, the vent riser is dry. I can raise the dogleg 6 inches above the WC flood rim. The shower is not wet venting the WC -- I had a plumber snake the vent stub and he said the WC sewer line heads off and is not connected to the shower drain at this point (see "trace of subpad sewer line" in picture 2). The shower P-trap is vented separately and ties into the washer drain on the far wall (see picture 3); that smaller 2 inch vent stack doesn't tie into the main vent stack until the attic.

    You're right, OD on 3 inch hubs are just shy of 4 inches. I will ream out these holes for extra clearance. Reach4 also suggested 45's and a wye, I just don't know if this would be a problem for practical access to the clean-out within wall, clearance-wise. Just to make sure I'm understanding correctly, is this picture more or less what you mean?
    s1.jpg

    The other possibility is just to run the vent stack vertically as before, although this might mean some tight spaces when installing the h/c water lines and shower rough-in. In that case, I would still need to have a ~16 inch horizontal arm to the clean out to reach through the wall to be accessible to the garage. Is there any problem with an extension like this?
    s2.jpg

    Thanks again.
     
  8. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Extension is not a problem.

    2 inch vent is enough for a toilet.
     
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  9. Texas_RSA

    Texas_RSA New Member

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    Mar 22, 2021
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    Hi Reach4, thanks for replies above. No the vent is for the toilet only. This wall is perpendicular to the garage wall. Vent stack PVC is 3 inch. Thanks for the suggestion re flush plug, hadn't seen these. I will keep the clean-out itself completely free of any studs, sitting just behind sheetrock and immediately accessible with via a removable panel.
     
  10. Texas_RSA

    Texas_RSA New Member

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    The vent is for the W/C (it just happens to be located adjacent to the intended shower pan); the shower drain vents separately (2 inch) in the back wall (see picture 3).
     
  11. wwhitney

    wwhitney Well-Known Member

    Joined:
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    Location:
    Berkeley, CA
    Thank you, sorry I missed that on my first read through. Looking down the vent opening in the slab, can you see how the vent is taken off the toilet drain? Given the geometry you have drawn, I would assume you have a san-tee with the toilet on the side inlet, and below that a LT 90 for the WC drain to go horizontal again. [I'm mostly just curious.]

    Is this WC at the end of the line on the building drain? If so are you confident there's not an end of line cleanout already? I think there's supposed to be one, and if there is, you obviously wouldn't need to add another. [Edit: rereading I see you mention that there was a cleanout before, so you need to put one in.]

    Not quite what I meant, and the fitting you've labeled "wye" is drawn as a combo. To get to my suggestion, replace the upper 45 with a wye where the side branch is vertical. Then the straight branch can continue through the wall to present itself as a cleanout at a 45 degree angle. Or if you want the cleanout entry to be horizontal, put another 45 on the cleanout leg.

    Of course, your drawing would be fine too. The advantage of using 45s is you don't have to be 6" above the flood rim level of the WC (if you use my suggestion and use a 45 for the cleanout to be horizontal, not sure if that horizontal cleanout should be 6" above the flood rim or not). 45 degrees from vertical is still considered vertical, DWV wise.

    Cheers, Wayne
     
    Last edited: Mar 22, 2021
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  12. wwhitney

    wwhitney Well-Known Member

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    Location:
    Berkeley, CA
    If it's 6" above the flood rim level. Below that elevation, UPC requires all vent fittings to be of a drainage pattern, so it would need to be a combo. Except that then the vent couldn't go horizontal, since there's no structural obstruction to just using 45s and staying vertical.

    Cheers, Wayne
     
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  13. Texas_RSA

    Texas_RSA New Member

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    Mar 22, 2021
    Location:
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    P_20210322_160542.jpg
    Hi Wayne, thanks for the clarification, sorry for my confusion. So, something like this?
     
  14. wwhitney

    wwhitney Well-Known Member

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    Location:
    Berkeley, CA
    Yes, that was precisely my suggestion. If you want the cleanout flush with the wall surface, then you'd need to use another 45. And if you do that I guess I think it doesn't matter if that 45 is not 6" above the flood rim, as that short horizontal section is not part of the vent path, it's a cleanout. The vent path is all vertical.

    Cheers, Wayne
     
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  15. Texas_RSA

    Texas_RSA New Member

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    Mar 22, 2021
    Location:
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    Got it, thanks very much for your suggestions. Guess I've got some more visits to Lowe's in my future.

    Also, in re to your post above,
    "If the vent riser is connected to the WC fixture drain as a dry vent, then yes the dog leg should be at least 6" above the WC flood rim level. On the other hand, if the vent take off is for the shower trap arm, and the shower is wet venting the WC, then your horizontal segment would only have to be 6" above the shower curb."
    When I had a plumber fish his camera through the vent stack stub coming up through the slab, he reported that it vented the toilet sewer line only at that point; the sewer line from the toilet heads downstream in the direction shown by the red dashed arrow in picture 2. I don't know why the builder used 3 inch PVC for a dry vent here, and the plumber remarked (as others have above) that he thought 3 inch was overkill for this purpose. He insisted that the shower drain does not tie in at this point, and the shower trap is vented separately in the rear wall (wall at the top of picture 1, also shown on LH side of picture 3).

    "Presumably you are going to be opening up the slab to move the shower drain, so you'll gain some insight at that time." Yes, indeed.
    Thanks again for your help. Cheers //rolf
     

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