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Thread: Leak between CI hub and Fernco donut...

  1. #1

    Default Leak between CI hub and Fernco donut...

    First, thank you for a great site. Since I found this web site and I found valuable answers to many problems. I usually use the search option and there is always an answer to problems that are similar to the problem at hand. Well, except today, here is my problem:

    I am remodeling a bathroom. The cast iron pipe under the toilet had a hole in it (pease see pic 1,) besides that the flange was loose. I removed the pipe. Removed the lead and oakum fiber, and cleaned the CI hub in order to install a 4" PVC pipe.

    I installed the PVC pipe in a Fernco donut, and used water and soap to insert the donut in the CI hub. I also used a block and a hammer to install the pipe/donut in the CI hub.

    From the other side of the pipe, I primed the pipe, then with PVC cement, I attached the 90 degrees elbow.

    Now, after two hours, I tried to test my installtion, and poured a bucket of water into the new pipe, and it leaks between the donut and CI hub.

    I removed the pipe, reinstalled it by reorienting the donut. Still leaks. It looks like the donut is not holding tight to the CI pipe (hub.) Although it is holding tight to the PVC pipe.

    Am I missing something here? Or should I use some type of glue/cement between the donut and the CI pipe? I thought this would be a straight forward solution.

    Please, I need your input. This is the only bathroom in the house. And during the remodeling process, I install the toilet at least one time a day, when I done working for the day. Unless I have to work for long hours, the kids would go to their grandmother. Well, I guess the kids will hit the trees tomorrow morning.

    Please find attached some pictures of the installation.

    Thank you,
    Attached Images Attached Images    
    Last edited by Terry; 07-23-2006 at 12:29 PM. Reason: to reattach pictures

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

    Default donut

    First, you have to realize that not all cast iron hubs were designed for a donut. If yours is old enough, it could have been cast with imperfections that make it impossible to seal a donut to it. But, normally, once you insert the PVC pipe into the donut, it should be almost impossible to remove without a jack of some kind. If it is separating easily, then it must not be putting sufficient force on the outside surface to force it against the hub.

  3. #3
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    Pull it out and check that the hub is clean. I wire brush mine till they almost shine. If it is fitting tight but has imperfections and continues to leak look very closely and see if there is a crack in the hub. If there is no crack and it is clean and fits tight but continues to leak you could try putting a thin film of silicone caulk on the donut and in the hub and assembling it. I see you like purple, maybe you should try primeing the pipe more.

    Last edited by Terry; 09-24-2009 at 04:43 PM.

  4. #4
    Plumber/Gasfitter dubldare's Avatar
    Join Date
    Sep 2005


    Also, look for either an SV(service) or XH(extra-heavy) stamped on the san tee you are connecting to. XH cast iron fittings have a larger hub than SV weight fittings. Likewise, the donuts need to be sized accordingly.

    If you used the correct donut, it should've been a pretty good fight to install the pipe and donut into the hub. (Lot's of beating and cussing!)

    If you used a ty-seal, get a donut instad.
    --Customers of plumbers: Never be afraid to ask for proof of licensure of the plumber servicing your equipment. A licensed plumber will be proud to show you his personal license.--

  5. #5



    thank you for your input. I just realized that it was easy to install. Little hammering and it was there. It was not made for this CI hub.


    If I like purple, would I install it in a drainage pipe?
    I thought of priming the pipe from both sides to clean it, and since the pipe was kinda short, I primed all of it.

    Well, I removed the donut, and cleaned the hub; tried again, and it was not holding tight. I did not even want to test it with water.

    I Insertted the PVC pipe alone in the CI hub. Took some of the old oakum fiber, and pushed it around the pipe very tight. It took more than an hour with a small screw driver. Until it was tight, and I filled the openening half way with oakum. Just like when it was under the lead. I supported the piple with some 2x4's.

    I had one stick of 2-oz of Plumber's Epoxy Putty. I wanted to try it out. I mixed some and push it around the pipe on top of the oakum. A little later, I was trying to adjust the support from under and around the PVC elbow, and it the pipe was tight.

    I went down to HD, and got 5 stricks of 4-oz of plumbers epoxy putty. It is very hard to mix a whole one of the 4-oz, let alone mixing all the sticks together. So, I mixed half a stick at a time, and pushed it inside, and made it very tight. Well, I was left with 2 sticks after I filled it and made sure it was tright.

    Now, after 4 hours (I got some sleep.) I just tried it and poured water and there are not leaks. The PVC pipe, and elbow don't seem to need any support. They are like a piece of the CI hub. But, I think I should support it.

    I hope what I have done today does not voilate any code, because next week when I am done connecting the bathtub, I will call for inspection.

    I don't think I will ever use the Fernco again. It seems from what I read, it is either too hard to install or too easy with leaks.


    Yes, exactly as you said, "XH" is stamped on the san tee. I checked it with a flash light. I saw the X, and I read the other letter with my fingers like the braille language. But it is there, the XH.

    I think, the donut I got from HD was for the Service hub. I saw one last week at Lowes that was a lot thicker. Probably, that would fit the XH. But, as you say it takes alot of beating and cusssing. Well, I've probably was cussing enough since yesterday, last night, and all day today. What a mess. I wish I left the brass ferrule on, it would have been much easier with the no-hub coupling. But, when I was cutting the lead piple, the recip. saw went into the brass ferrule, and I had to remove it.

    Thank you for your imput, I wish I read it yesterday. Well, we learn.
    Last edited by knight_2004; 05-15-2006 at 08:23 PM.

  6. #6
    I&C Engineer (mostly WWTP) Lakee911's Avatar
    Join Date
    Aug 2005
    Columbus, OH


    Cool. Hope that works for you. I've heard of leading a PVC/CI joint before too...but I'm sure thats more work than the donut would have been anyhow,


  7. #7


    I am going throught the same thing and the donut won't hold well. I am planning to switch to a 6.5" x 4" no-hub coupling. I was going to ask why didn't you go this route insead of all that work but then saw your last post. I really don't want to have to do that.


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