PVC DWV connection to Cast Iron Hub

[MrPither]

This is related to an earlier question I had.

I have a 1928 era cast iron (CI ) DWV main stack (I believe it is extra heavy rather than service weight). It has two hubs/bells right next to each other - one is ~3" ID and the other is ~5" ID (more like 5.2"). I found a Fernco donut (22UX-205) that fit quite tightly into the 3" bell and it now holds a short section of 2" PVC DWV pipe. It was difficult to get in (as it should be) but should make a water tight seal.

The 5" bell, however, I could not get to work with a Fernco donut (Fernco 44UX-305 (5.05" OD) for use with a 3" DWV PVC pipe inserted). The bell is probably just a bit too large for the the donut. The donut does fit, and is somewhat snug, but not nearly as tight as it should be to be safe. The next size Fernco donut will be too large to fit.

My question is, since this is going to be the toilet DWV hookup to the main DWV stack, how should I approach connecting 4" (or 3") PVC DWV pipe to this 5.2" ID CI bell? My current plan is to insert a short section of 4" PVC sched 40 pipe into the bell, pack around it with oakum (half the depth of the bell) and then use plumber's epoxy putty to seal in the oakum. I'll then hookup the rest of the toilet PVC DWV line using a 4" to 3" reducing coupling, etc..

Does this sound like the best plan? Thanks in advance for your help.

As I had shown before, here's an old photo of the CI stack and two bells (I have since removed the ABS DWV piping, lead wool and oakum seal you see going into the 5" bell on the left) ... I abandoned all hope of hooking up ABS pipe and fittings to what was there, as ABS DWV plumbing has become impossible to find.

[MrPither]

Well, I went ahead and filled in the area between the 5" CI bell and short section of 4" PVC pipe with oakum thread (half way up the depth of the bell) and then I used Plumbshop's Plastic Lead to fill in up to the flange of the bell.

I found the Plumbshop Plastic Lead part #PS2960
(http://catalog.plumbshop.com/Default...tID=M375&Abs=1) to be rather crumbly and difficult to pack into the space. It claimed it was like putty, but as crumbly as it was, I don't how well it will work. I suppose its main job is to hold in the oakum and keep the pipe in place, so it may do the job. However, my experience with plumber's epoxy is that it is quite firm and a bit sticky but never crumbly. It's much easier to work with. I may end up having to redo it using plumber's epoxy. Either that or apply plumber's epoxy to the outside as a final seal.