Splice a Tee into cast iron stack

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DIYorBust, Jul 20, 2020.

  1. DIYorBust

    DIYorBust Active Member

    Joined:
    Mar 5, 2019
    Location:
    Long Island, New York
    Hello,

    I would like to add a tee to a cast iron 4" stack to run a branch for a washing machine. I'm thinking about using a riser clamp and 2x4s to support it above the cut.

    I'm also concerned that I won't have enough play to get the tee and the couplings installed. Is this likely to be a problem? Am I missing anything else? I really want to be careful with this project.

    Thanks!

    DIY
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    You intend to use two cuts and two shielded couplers, right? I expect you will final-cut the PVC assembly after cutting the cast iron, and measuring the gap.

    You will measure the OD of the cast iron to make sure you get the right couplers.
     
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  4. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    The cut is 1/4" more than the fitting assuming you cut it square. You can get by with a little more than that too. The rubber gets rolled back, fitting placed inline, and then the rubber rolled back over the new fitting. The the shielded part slides up and over it.

    You can use a snap cutter which cuts a a square cut, or use a sawzal blade designed for cast. Diablo makes the best ones.
    Eve protection always.
    I do not use a grinding wheel. Too much bad stuff can happen.

    Sometimes I pick up a no hub cast fitting to insert there.
     
  5. DIYorBust

    DIYorBust Active Member

    Joined:
    Mar 5, 2019
    Location:
    Long Island, New York
    Thanks folks. @Reach4, I am planning use two cuts and two shielded couplings, yes, but I'm planning to use a no hub cast iron tee rather than transitioning to PVC.

    @Terry I'm planning on the sawzall to cut this with a diablo carbide blade. I'm toast if the pipe breaks in bad way as I don't have good access to the next coupling, and I've heard that the snap cutter can damage the pipe. I guess I'll just have to be careful to cut it square. Any tips on this?
     
  6. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    If you are absent minded, and forget to slide the shield on first, you can still add the shield later. It's more work than if you did not forget.
     
  7. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    You can place some tape around the pipe to added as a visual guide when cutting.
    The Diablo blade is what I would use there. Snap cutting works okay on new pipe. With the old stuff it can get a little weird.
     
  8. Jeff H Young

    Jeff H Young In the Trades

    Joined:
    Feb 27, 2020
    Location:
    92346
    Good advice above! i gotta get a real blade for cutting cast its a PITA sometimes with standard blades on saws all. I think its cleaner/better putting a cast iron fitting even if then going to plastic for something new.
    The cut is critical to a degree not too much or too little!
     
  9. gagecalman

    gagecalman Member

    Joined:
    Nov 25, 2016
    Location:
    Baltimore, MD
    As already stated the Diablo carbide blades work great. I use some oil to lubricate the blade while cutting.
     
    Jeff H Young likes this.
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