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Thread: Replacing Cast Iron Pipes

  1. #1

    Default Replacing Cast Iron Pipes

    My husband and I are in the midst of renovating our 1st home, built in 1850. Needless to say, we are having some problems.
    While tearing down wallboard in the first floor bathroom, I came across the cast iron pipe for the plumbing to the upstairs half bath. (The toilet had been leaking, so we had previosly shut off the water to that upstairs room.)
    The pipe had 3 pieces of metal flashing-type sheets, wrapped with wire to hold it to the pipe. When I took off the flashing, I discovered that the back of the pipe had disintegrated, thus the leaking. It is approx. 4 feet in length that will need to be replaced. Should we remove the whole pipe and install new PVC plumbing, or just cut the damaged piece and go from there? Oh, I forgot to mention that we have NO plumbing experience!
    Any advice is great!
    Thanks!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Those pipes served that home well, probably for nearly 100-years or more. It's probably time to replace them. These things are HEAVY, and can injure you or damage the building if they fall. So, some would consider having a pro to do this. It is doable if you are careful.

    A saw to cut the stuff is slow and a pain. Better to rent a cast iron chain cutter. This wraps around the pipe, you tighten it up, and it cracks the pipe. Yours may crush, but the end result will be the same, you will have made a break in the pipe. Wear gloves, safety glasses, and long sleeves in case a shard decides to jump out at you. Where the pipe goes through a floor or ceiling, ensure it is supported so it won't fall - there are special clamps designed to do this.

    Both PVC and cast iron will last a long time. The cast iron will be quieter but harder to install. If allowed in your area, they also make a foam core pvc that is supposed to be a little quieter (and lighter). It is NOT as strong, so that might also be a consideration. Most places just use the solid stuff. Maybe one of the pros will comment.

    If the drain lines out to the sewer are cast iron, they could be in fine shape, or similar to the stuff in the house. Hard to tell without a good inspection.

    Last thing I can think of, there's probably a lot more. What you have probably doesn't match current codes and practices, so you probably shouldn't just copy what is there; you'll need to get some advice to get it right. Come back with questions as you have them...
    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
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    As Jim notes, it's feasible to do this yourself, but it's an awfully big job especially for your first plumbing experience. I think it would be very prudent to have your entire system inspected. Have a camera check the underground line. I would really hesitate to try to patch this up. How many more places have failed or are ready to fail. I would bet there are numerous connections that are not even close to code in regard to vents, traps, pipe size, etc.. As far as what material to use for replacement, cast iron is probably the best but is not a DIY job and is spendy. Plastic pipes (PVC or ABS) are much easier to use, are less expensive, and will last as long as you will ever need to worry, but the water does make noise as it passes through.

  4. #4
    Plumber Cass's Avatar
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    What is the diameter of the pipe you want to replace?

  5. #5

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    The pipe is 16" in diameter.
    The whole thing is in very rough shape, as is most of the plumbing. We want to do the right thing, as inexpensively as possible, without compromising the integrity of the job. This is only one thing in a very long list of projects to accomplish.
    Thanks!

  6. #6
    In the Trades Gary Swart's Avatar
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    I don't think you mean 16" diameter. Most likely 4".

  7. #7
    vaplumber
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    If you can replace all of the pipe, great! If not, then support it correctly with riser clamps, cut it off, and use the proper connectors to add to it with the pvc or abs. I prefer abs on inside waste lines, but pvc will also work great. Your underground piping may be either tile, or cast iron. I would recommend the camera inspection, and replace anything that is questionable.

  8. #8
    Plumber Cass's Avatar
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    If you don't do the job right you might have the whole pipe come crashing down on you and the house. I'm talking about the part that go up through the wall and roof from where you cut it. Cast iron is very heavy. It needs to be supported corectly B4 cuting it. I suggest getting a few estimates then decide if you want to tackle it.

  9. #9
    In the Trades Bob NH's Avatar
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    Since you are in a renovating process, you might as well consider renovating the plumbing.

    You might start with a plan that is based on "What do we need to continue living here?". Then do a systematic removal and reconstruction of the plumbing system while the sheet rock is off the wall. I would never cover up a 100 year old cast iron pipe, regardless of its apparent condition. And I would never cover up iron supply pipe.

    Maybe you can find an easier place to start your plumbing experience and work up to the 4" cast iron.

    While you have the sheet rock off you might also look at the wiring.

  10. #10

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    We are updating all the electrical as we go (knob & tube everywhere)....we have finished the kitchen and the full bath was our next project. There is no doubt that all of the plumbing has to be updated as well but we were hoping to do it as we are the electrical, one thing at a time. We would never try to patch this problem and then put the walls back up as the previous owner has done, we want to do everything once - and correctly! This sounds like a very big job, but we can't afford to do everything at once. Would a licensed plumber do just one job, even if he noticed other things that were wrong?

    As far as the size of the pipe - my husband has told me the error of my ways...4" in diameter (16" circumference). Thanks!

  11. #11
    I&C Engineer (mostly WWTP) Lakee911's Avatar
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    I figured you meant 16" circumfrence. That's actually a good way to findout the diameter of a pipe when you can't see the cross section. Divide by pi and then lookup in a table with OD to find ID of a given type.

    Jason

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