Hi,

I am trying to use a Fernco flexible rubber connector to mate 3 inch PVC (3.5 inch OD) to existing cast iron having an outside diameter of 5.875 inches. No problem with the PVC side, but hard to find the cast iron size. A Fernco 1002-43 has internal diameters of 5.25 inches and 3.38 inches. The outside diameter of the cast iron is 5.875 inches.

Will the 5.25 inch ID Fernco stretch enough to cover the 5.875 inch OD cast iron?

If it does, will it be extremely difficult to attach it to the cast iron?

How much larger diameter can a Fernco fit on?

I know that there may be closer fitting Ferncos, but no one has them in stock and they would take over a week to deliver.

Sounds like you are trying to install the fernco over the cast iron hub… it will expand with some heat or search for cast iron x clay fernco, although this is not a preferred connection

Thanks, yes it is over a hub. The pipe above rotted away over 80-95 years. The cast iron section remaining is about 2 feet down and through an 18 inch wall when it changes to clay pipe. Most of it is hub or elbow and seems solid. All PVC above. Sort of an emergency to get a toilet running though.

I plan to remove the cast iron and add a new bathroom in the future, so this is just a temporary work around.

i only did this once in an emergency.

if i remember right, i used a 6 inch fernco to go over a 4 inch hub. it clamped right to the hub.

i believe it was a 6 x 4 fernco ???

I took a slightly different approach in dealing with old cast iron, and the pros here will likely spit a little a coffee reading this....

I had a similar situation with a 2" inlet on a cast iron san tee. I cleaned out the hub, degreased it with Brakleen, threaded a male adapter into the hub as far as it would go, and then poured fast setting epoxy between the PVC pipe and hub. The epoxy bonded well to the cast iron and once it was set it was a solid joint, didn't leak a drop. Then just glue up the PVC stub to the rest of the plumbing.

You could do the same here with the 3" section. I don't like a Fernco on the outside of the hub when it's on the bottom side of a vertical connection, it will take a miracle for it not to leak.

Here's the epoxy I used [www.homedepot.com].

If the hub is still solid, no crack no rusting, why can't you get a short piece of cast iron pipe (or even PVC) and join to it, you can use cold caulking compound instead of molten lead, then from the other end of this short CI pipe joint to the PVC with the proper Fernco coupling?



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You might try the 1051-44 with a 4x3 bushing in the cast iron side. It will be easier to stretch from 5 3/4" to 5 7/8".



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How about a 4x3 donut?

Well, can't finish job before trip to big city, so I hope to find a 1006-43 which is 5.61 to 3.53.

Problem is living in a small town, there are limited choices.

Most of these specialty items can be ordered online. Even a big city plumbing supply store may not carry all the items and they may need to special order.

CONCLUSION: Amazingly, I found a Fernco P1006-43 on eBay with interior dimensions of 5.61 inches and 3.53 inches. Even though space was tight, I got the Fernco over the 5.87 cast iron. As for the 3 inch PVC it slid up and down through the Fernco so the 3 inch PVC extended about 14 inches into the old cast iron and I was able to avoid using a repair coupling. I inserted a 3 inch hub/hub/test tee for future clean out in the vertical line and was done.

ANSWER: I doubt if a Fernco 1002-43 with a 5.25 inch diameter would ever stretch enough to go around the 5.87 inch cast iron. Especially with restricted access like I was faced with, it couldn't be done. The 3.53 diameter was nice because it allowed the PVC to slide up and down. Hence, when using a Ferno, forget their descriptions (Clay/cast iron/Plastic/Concrete); instead use the appropriate Fernco interior dimensions needed for your job.



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