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Thread: Fernco donut or similar product for 4" XH cast iron hub

  1. #1

    Default Fernco donut or similar product for 4" XH cast iron hub


    I've run into a snag and I'd appreciate help.

    I just removed a pipe (4" toilet drain) from the 4" hub of a cast iron sanitary tee (I think...plumbing terms frustrate me). This was an arduous task. After much advice, I accomplished it by drilling as much lead as I could from the oakum and lead sealant until the drain turned (reluctantly with help from a 4' piece of pipe for leverage). I then cleaned out the rest of the lead and oakum and prepared to insert the Fernco donut and PVC adapter (4" PVC to 3" PVC) sold to me by our local plumbing supplier.

    The fit was very loose and not at all as described (I was told I would need to use considerable force to insert the donut). I've since read in this post (http://www.homerepairforum.com/forum/showthread.php?t=3106) that I have a 4" XH (stands for "extra heavy?") hub and that the Fernco won't fit as it is too small.

    Went to the Fernco web site and they claimed that they need to know the exact dimensions within 1/32" as well as the manufacturer to supply the correct donut as they make hundreds of configurations and precise fit is crucial for a tight seal.

    Regarding the dimensions, the inside diameter varies from 4.98" to 5.25" and I doubt they need to know the dimensions within in 1/32" as the surface variations in the cast iron certainly exceed those tolerances. The hub appears to be 2.5" deep to the start of the "bevel." The manufacturer is most likely Sommerville (as stamped on the cast iron) and there is also a stamp of SIW (Sommerville Iron Works???).

    I like the idea of using a PVC bushing or donut as I have little skill with oakum and plastic lead. Is anyone familiar with this issue and do you have a solution?

    How do I mate a 4" cast iron XH hub (5.25" ID, 2.5" deep) with 3" PVC pipe?

    I can provide pictures if it is helpful.

    Thanks in advance for any input. I plan to call Fernco as well as talk to our plumbing supplier tomorrow. I will post anything I learn.


  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default hub

    Are you guessing you have an XH hub, or do you actually see the letters XH on the fitting. Early cast iron pipe hubs were made to very loose tolerances because the lead would accomodate any variations. Personally, I woudl repour the joint rather than go through the hassel of trying to mate a rubber gasket with the joint.

  3. #3


    The letters XH are stamped on the side of all of our cast iron fittings.

    The only problem with repouring with oakum and plastic lead is that I wouldn't be able to use the existing hole in our floor joist.

    I'm calling Fernco right now.

    One of the other solutions (suggested by the plumbing supplier) is to "shore up" the connection with the very slightly loose donut with some sort of sealant (such as silicone or gutter seal).



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