inserting 3" PVC in old 3.5" cast iron as a liner!!

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by switchex, May 30, 2014.

  1. switchex

    switchex New Member

    Aug 11, 2006
    I have to replace old and cracked cast iron that goes from the basement into the street about 6 feet before reaching the city sewer line. I am calling a couple companies to get estimates for either a liner or a total replacement. Once they give me a line to the inside of the house, i can do the rest of the job.

    However, I have been thinking of a way of doing the job myself!!! assuming the old line is straight with a 3.5" diameter, would it be possible to clean it out and insert a 3" PVC in it? I can use a camera to see how far I should insert the PVC in and stop few inches before reaching city line.

    Did a lot of research have not seen anyone doing this .. whether it is a good or totally stupid idea, i am surprised no one has tried it!! what do you think?

    Do I have any other do it yourself/cheap options?

  2. Tom Sawyer

    Tom Sawyer In the Trades

    Nov 29, 2010
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  4. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    The plastic pipe WOULD NOT slide inside the cast iron. but if it did your plastic would have to be undersized. IF the cast iron is really 3 1/2" that would be the O.D. which is the same as 3" plastic ".No one has tried it, because they realize it would be a "dumb idea" for many reasons.
    Last edited: May 30, 2014
  5. dj2

    dj2 In the Trades

    Aug 13, 2013
    1. First you need a camera check to see the inside of your main drain line.

    2. Another option to pipe replacement is relining. However, you need to find out if it's feasible in your case. If not, you're looking at replacement. Prepare money.
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