Which coupling for 3" PVC to 4" Cast Iron

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by takelargebites, Dec 15, 2011.

  1. takelargebites

    takelargebites New Member

    Messages:
    18
    Location:
    NC
    I need to connect my new 3" PVC drain line to the old 4" cast iron drain. The pipes are on the horizontal in the basement. Which Fernco coupling would be preferred? The 1056-43 Flexible coupling or the ProFlex 3000-43 ? It looks like either coupling would accomplish the same thing but it seams like the ProFlex would be more resistant to shear since it's banded.

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    Last edited: Dec 15, 2011
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,062
    Location:
    Cave Creek, Arizona
    You are correct, especially since the "Fernco" cannot be used for that application.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,316
    Location:
    Bothell, Washington
    Above ground is when you need a shielded coupling; required by code.

    Plumbers always use shielded couplings.
    There are times in the ground, when you can use a non-shield coupling, since the ground is supporting.

    When you join pipes, it's important to measure the OD of the pipe.
    A new 4" cast iron pipe would be 4-3/8" OD
    An old 4" cast iron pipe can be as small as 4-1/8", which is considered a copper pipe size.
    If I have copper pipe size cast, then I use a mission copper coupling x no-hub. Which does work with PVC if it's standard waste sizing.

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    Last edited: Nov 7, 2013
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,062
    Location:
    Cave Creek, Arizona
    quote; I generally only use banded ones myself, but thought they were only required underground.

    That is the ONLY place they are NOT required, but usually outside the building.
  5. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,705
    Location:
    Chicago, IL
    In Illinois shielded couplings are required underground. And above ground we are allowed to use no-hub couplings but must use a no-hub transition adapter on the PVC and or ABS pipe.

    Attached Files:

  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,062
    Location:
    Cave Creek, Arizona
    When I was in Chicago, we never used PVC, ABS, OR No-Hub cast iron.
  7. takelargebites

    takelargebites New Member

    Messages:
    18
    Location:
    NC
    My cast iron measures 4-1/4" OD. Does it sound like a Mission CP 43 (4" CI to 3" PL, ST, or XH CI ) would be the way to go? I'll see what the supply house has tomorrow morning and then track down an inspector to get his ok too.
  8. SewerRatz

    SewerRatz Illinois Licensed Plumber

    Messages:
    1,705
    Location:
    Chicago, IL
    I did not say Chicago, said Illinois. When I work in Chicago, we do not use PVC, ABS or no-hub. Still lead and oakem.
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