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While removing the toilet the The previous flange came off with it. We suspect that is what was causing a leaking issue on the ceiling below. So we went to replace it with an extender flange but the 4 inch extender flange is not getting a tight seal on the cast iron pipe. What are my options?

  • this may, or may not work ... look about 1/2 way down this page ... doityourself.com/forum/plumbing-piping/… .... use the "donut" in the cast iron pipe and use a regular flange with a glued on short piece of pipe
    – jsotola
    Dec 13, 2019 at 0:29
  • I guess you don't have any access to the inside.
    – Ride Sun
    Dec 13, 2019 at 0:54
  • I have access from below. There is a spot in the downstairs ceiling that we are fixing and I can clearly see the pipe from there. Dec 13, 2019 at 1:06

4 Answers 4


It sounds like you can get at the pipe from below. I would highly suggest cutting some of the cast iron away and using a rubber gasket coupling (i.e. a Fernco) to transition to PVC. Then you can put a regular PVC pipe flange up there and avoid the problem of depth entirely.


Open the Floor from rafter to rafter(circular saw). That gives you access to the area you are working on. Later you cover that area with a piece of plywood of the same thickness and support the piece with the existing rafters and some sistered in 2x4's.

I bet the old cast iron is laying on the ceiling below and that's why you don't get a tight seal. Support and lift the cast iron a bit up that you get the right heights. That will give you the seal. The key is that you really see what you are dealing with. Good luck.

  • I have access to the pipe from below because we are repairing the leak damage. It looks like they have some metal support s tied to the 2x4's. Because of the age of the house (1964) I can tell they the supports were added on later so it may have been laying on the ceiling. I bought the house with this damage and am trying to make sense of thier attempted fix. Dec 13, 2019 at 1:12
  • See if you can lift the pipe by hand and bridge the gap. If you can I would tie the pipe again. Maybe, this time more durable. Maybe a 2x6 with a round cutout holding the pipe. Pictures would help ...
    – Ride Sun
    Dec 13, 2019 at 1:20

They have toilet flanges that are longer then the one in your photo. Yours looks like four inches. The one pictured below is 6 inches long and might be long enough to solve your problem.

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You'll probably need to go to a plumbing supply store to get one. Good luck.


That style of PVC flange will not provide a good seal to the cast iron hub below. Originally, the flange would have been cast iron and was connected to the soil pipe using a combination of lead and oakum, which is a hemp fiber. The oakum would be packed in around the fitting, and lead solder would get ladled over the top to make it water proof. The purpose of the oakum was to prevent the solder from falling through the gap in the pipe before it solidified. The original flange must have been removed as part of a bathroom remodel at some point.

Using lead and oakum is still used occasionally, but many installers have switched over to hubless fittings, which are connected by a type of coupling known by the brand name Fernco. To install the new one, use a reciprocating saw to cut the bell off the end of the cast iron pipe and use a piece of PVC pipe the same diameter to extend it to the proper length. Once that part is done, you can then install a standard toilet flange, and it should not ever leak again.

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