Increasing the slope of a drain from level copper to sloped PVC

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by LikeABigFriedEgg, Sep 12, 2021.

  1. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    Hey everybody,

    I am replacing a horizontal six foot section of 1-1/2" copper drain pipe in a wall with 1-1/2" DWV PVC. The holes through the 2x4 studs are 2" and round.

    The section of copper I'm replacing was almost level (1/4" in 5 feet), which led to corrosion, which is why I am replacing it. I'll be vertically enlarging the tops of the holes to get get some room to put some slope on the new pipe. I have two questions.

    How can I join the more sloped (1/4" per foot) PVC to the almost-level copper? Does anyone ever apply a heat gun or similar to PVC so as to produce a local bend of say 1.2 degrees (about the same as a 1:48 slope). I'm planning on DWV pipe, but I could use schedule 40 on the section being heated and bent. Would that matter?

    The house was built in 1968, so I expect the studs are stronger than 2x4's are now. Is there much reason not to enlarge the holes vertically? One of the holes would have to be enlarged about an inch vertically, the others less.
     
    Last edited: Sep 12, 2021
  2. wwhitney

    wwhitney Well-Known Member

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    To join the 1-1/2" copper DWV to 1-1/2" PVC you'll need a Fernco 3001-150 or a Mission CK-115 coupling. Hopefully they will accommodate a 1 degree misalignment. Ideally you'd correct all of the mis-slope, so you don't need to accommodate a 1 degree misalignment.

    Increasing the hole size in the stud vertically by up to an 1" shouldn't do much or any additional weakening of the stud. Depending on how many studs are involved, and whether the wall is a bearing wall, it may be appropriate to double the studs and/or to use metal stud shoes to reinforce the drilled region.

    Cheers, Wayne
     
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  4. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    Thank you, Wayne. I'm looking at the label of the Fernco 3001-150. Could you help me with the abbreviations? It says
    1-1/2" CI, PL, or ST to 1-1/2" Copper or 1-1/4" PL

    https://www.pipingengineer.org/piping-abbreviations/
    CI seems to be cast iron.
    What are PL and ST? Plastic and steel?
     
    Last edited: Sep 13, 2021
  5. Jeff H Young

    Jeff H Young In the Trades

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    cast iron , plastic , steel = ci pl st
    sure open the holes up to allow fall keep it to a minimum though we are talking 4 studs hopefully non load or minimal . might need a plate over those studs or a shoe
     
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  6. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    One of the studs is a king stud, next to a window. It seems to be two 2x4's nailed together. One of its 2x4's is cut off about 7-1/2" above the sill plate though. The other 2x4 is bearing all of the king stud's load on the sill plate. Is that something I should try to correct? Of the five studs I can see, the tops of the holes of three of them are bearing down on the existing pipe. That king stud is one of them. I don't detect any rot in the sill plate or studs.
     
    Last edited: Sep 13, 2021
  7. Jeff H Young

    Jeff H Young In the Trades

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    sorry not a carpenter or structural engineer
     
  8. wwhitney

    wwhitney Well-Known Member

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    A picture would help. Sounds like a load bearing wall, so some reinforcement is likely in order.

    Cheers, Wayne
     
  9. Reach4

    Reach4 Well-Known Member

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    Is this for a kitchen or bathroom, or what? You understand that 1-1/2 inch PVC is considerably bigger diameter than 1-1/2 inch copper.

    Some people have bent PVC, and packing sand inside before applying the heat prevents the pipe deforming. However PVC will bend slightly. There is solid PVC and foamcore PVC. They look the same except on the cut end, but foam core. I think I would want solid for heat bending. I have never done it.

    How about running a new drain pipe under the floor, in the basement or crawl space?
     
  10. Jeff H Young

    Jeff H Young In the Trades

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    possibly, don't know why they'd be hacking up king studs and such if just drilling a hole in floor was a
    simple option you never know with no pictures or idea what this job is about, 1.2 degree bends and odd ball stuff going on here
     
  11. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    Sorry to leave out some details.

    Yes, I know that the PVC DWV replacement pipe is 1.9" OD. I was going to replace with copper until I got into the wall and found that the stud holes were already 2" so that I wouldn't have to enlarge them horizontally.

    This is for a vented kitchen drain pipe. Part of the wall is behind the kitchen cabinets, and that is the part of the wall that I have opened. There is another 3' of wall downstream, behind drywall only, that I have not opened.

    The wall is atop a slab (around 20' x 24') which is next to the basement. The pipe goes inside the wall about 10' then goes down to the basement, from there to the sewer. At some point hidden in that wall there must be two elbows with a roughly-one-foot vertical section of pipe in between so that the drain pipe can enter the basement horizontally just above the poured wall.

    The pipe looks horrible, but somehow the leak came on suddenly, and the sill plate seems sound.

    IMG_3343.JPG IMG_3344.JPG IMG_3346.JPG

    Diagram forthcoming.
     
    Last edited by a moderator: Sep 13, 2021
  12. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    Here I've laid things out in a diagram.

    kitchenDrainRepairDiagram01.jpeg
     
  13. Terry

    Terry Administrator Staff Member

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    It's common for copper DWV to rot out over the years on a kitchen drain.
    I would consider giving that some grade by drilling new holes, a bit bigger so that you can run PVC or ABS.
    It's too bad where if finally connects isn't open. Whatever is left is due for replacement at some point. If you could find that area, I would consider dropping the line a bit so that you can just drill new holes over to the sink.
    2-1/8" is the smallest hole you can use for 1.5" PVC, and 2-1/4" is even better.
     
  14. wwhitney

    wwhitney Well-Known Member

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    Sounds like it's worth opening up the 3' of drywall to replace that section of copper DWV as well; drywall is repairable.

    I don't see a picture of the king stud and the cutoff stud next to it. Is the cut off stud on the window side of the king, or the other side? If it's on the window side, a picture up the stud bay towards the rough sill of the window would be of interest; if there's a remnant jack stud up there, it would probably make sense to do a repair. But it's not necessarily a problem, the lack of a jack stud is a little unusual, but they could have used a header hanger to support the header over the window from the king stud.

    As to the holes in the studs, I would carefully enlarge them as required, and then reinforce each single stud with a Simpson HSS2-SDS1.5, or HSS2-2-SDS3 for double studs.

    Cheers, Wayne
     
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  15. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    What about a coupling that would be more flexible? That Fernco fitting can handle 4.3 psi and is designed so that it can be buried, a bit more capability than I need. It's a one-story house, and only the kitchen sinks drain into that line. The greatest pressure on this fitting will be a couple feet of water in case the sinks back up, just about 0.6 psi.

    I'm not worried about the $7 for that coupling: I find that the stub of the remaining copper pipe is a pretty thin on the bottom, so I'm kind of worried about crushing it. It would be good to replace all the copper in the wall right now, but some of it is a little tricky for me, and I want to save that for another time.
     
  16. wwhitney

    wwhitney Well-Known Member

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    Actually if you look at the product page on Fernco 3001-150 you will find that it is listed for above ground use only. The more long, more flexible style without an outer shield is listed for underground use only.

    Assuming you are in Iowa, you're subject to the UPC, and the following section applies:

    https://up.codes/viewer/iowa/upc-2018/chapter/7/sanitary-drainage#705.10

    Basically your only choices to connect copper to plastic as I see it are to use one of the two shielded couplings I mentioned, or to solder on a copper female adapter and use a plastic male adapter with pipe dope to make the connection. And the shielded coupling has to be the better option, I would think.

    Cheers, Wayne
     
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  17. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    Presumably you are quoting code about the minimum diameter. I have removed the old copper and am able to fit the 1.5" PVC through each hole pretty easily. What can you say about the rationale for a minimum 2-1/8" hole?
     
    Last edited: Sep 13, 2021
  18. Reach4

    Reach4 Well-Known Member

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    How far is the left edge of the cabinets from the space above the basement?
     
  19. LikeABigFriedEgg

    LikeABigFriedEgg Member

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  20. LikeABigFriedEgg

    LikeABigFriedEgg Member

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    Something like 40 inches.
     
  21. wwhitney

    wwhitney Well-Known Member

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    Not listed for above ground use.

    As to the holes, if the pipe will fit, that's fine. But if you are only testing the holes one at a time, you may find out they are not aligned in the dimension perpendicular to the wall.

    If you can drill your new 2" holes accurately enough, it will work, but it's hard to be that accurate. You could make a guide fixture to ensure your new holes are the same distance from the front edge of each stud, and then find out those front edges aren't actually all in plane with each other.

    So 2-1/8" is a practical minimum.

    Cheers, Wayne
     
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