(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 5 of 5

Thread: Removing waste pipe from foundation wall

  1. #1

    Default Removing waste pipe from foundation wall

    My home's cast iron 4" gravity waste pipe fractured comletely off at interior edge of 15" thick foundation wall. A second complete fracture exists 9" outside foundation. Pipe is strongly bonded to foundation concrete, and the concrete is over 50 years old. Is it acceptable to descale interior of pipe and retrofit by running 3.5" PVC through existing hole and using reducers at each end to unite remaining waste pipe?? Otherwise, is core drilling the only way to remove pipe/enlarge hole to fit 4" piping to match? -- Desperate for solutions. thanks!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Hammer and chisel? If the pipe is 4" elsewhere, you can't throttle it down to go through the wall.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    If I read your question correctly, you want to go for 3" PVC (no such thing as 3.5") to 4" cast iron then back to 3" PVC. If that's what you are suggesting, the answer is no. You can not decrease the size of a drain. If it was my job, I'd use a rotary hammer/drill with a long 1/2" bit and drill around the CI from both sides, removing as much material as possible. Then a good sledge hammer on the end(s) of the CI should break it out.

  4. #4

    Default Thank you, Gary and Jim

    That's what I was afraid of...not OK to reduce a waste pipe. Time to earn some of that sweat equity!

  5. #5


    Took your recommendations to stick with 4" piping. Rather than chisel, rented ($70) a chipping hammer which melted the concrete like butter, easily loosening the existing cast iron and also allowing me to slightly enlarge the hole so that I can pass the thicker walled 4" PVC through. Worked like a charm, now will add a backflow preventor outside the wall. Thanks again!


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts