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Thread: To Replace Cast Iron or Not to Replace That is the Question

  1. #1

    Default To Replace Cast Iron or Not to Replace That is the Question

    So here is my problem. As you can see from the photos, my existing stack is cast iron. I need to tie a new 4" branch into from a new bathroom.

    My problem is that the new branch is lower than the current 4" PVC branch from the old bathroom. So I can't tie into the old hub. The old vertical WYE on against the wall is a 4x4x2. So I have to change that WYE in either case.

    So inclined to replace all off the cast iron with PVC up until the house trap as shown in the photos. My 2nd photo includes my suggested layout and use of new PVC fittings.

    If I do change all the CI to PVC, then I guess that I have the option to lower all the fittings and bring the new branch in right under the stack, instead of extending it to the WYE.

    I would appreciate comments and suggestions.

    How hard would the CI removal ?

  2. #2
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
    Join Date
    Jun 2009
    Penticton, BC


    Quote Originally Posted by highpeakscontracting View Post
    I would appreciate comments and suggestions.

    How hard would the CI removal ?
    How skilled are you with plumbing?

  3. #3


    Depends what you consider skilled. I'm NO master plumber, but I've done about 25 bathrooms over the past 10 years or so. I've just never had to work with CI that much except for a lead toilet bend replacement or a saddle. Why do you ask?

  4. #4
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    I think he is asking about your experience because this is a fairly big job for a DIYer, especially one with little experience. Many folks think the hard part of plumbing is installing all of the water supply lines, but in reality, water lines can be run in pretty unorthodox ways and still work quite nicely. However, the sewage system has many pitfalls. It's very easy to use the wrong fitting, or even use the right fitting the wrong way, and venting is a challenge especially in redoing an older home. Does your local area still require whole house traps? They are pretty much a thing of from the past in most places. In your favor is the fact the pipes are all pretty well accessible, but it's still a major job.

  5. #5
    Extreme DIY Homeowner Scuba_Dave's Avatar
    Join Date
    Jan 2009
    South of Boston, MA


    Sledge hammer worked for me
    Cut it where I wanted to leave the rest
    But I ended up changing my mind after I had part cut & taken out
    Good thing too as the stuff in the basement was clogged solid for 2'
    DIY Handyman (not 4 hire)
    I have enough to do to my own house

  6. #6
    Network Engineer rmelo99's Avatar
    Join Date
    Jul 2006


    From one DIYer to another. Removing that stuff is a pain. Cast isn't too bad if u have a snap cutter and can break it into small enough sections that are easy to handle.

    I removed all mine bc i didn't want to have any old piping buried in the walls after doing a major remodel. I have 3 stacks in my house, 2 of which were 4" galvanized pipe! Your lucky bc that stuff can't be cut with a snap cutter.

    The pros of PVC is that if you do your own work at the house it is a million times easier to work with down the road.

    Since yours is in the basement you can easily get to anytime...

    One gotcha that I don't think anyone mentioned is that if you remove cast iron from below that stack the upper/vent side needs to be very very well supported or you will have hundreds of pounds of piping coming down on you fast.

    Some juristictions do not allow pvc below cast...FYI


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