I need to fix a leak that I probably started in the first place when
gutting out my bathroom. There’s some cast iron fittings under my toilet between the closet flange and the main soil pipe leaving the house. One of them has a 90 deg. elbow that I’m presuming is 2″ dia. A 1.5″ dia galvanized pipe used to fit into this elbow like this: The end of the galv. pipe is threaded and there’s a sleeve about 2″ wide screwed onto it, presumably to increase the O.D. of the pipe by about 1/4″. This goes into the hub (I hope I’m using the right terminology. The end of the fitting flares out to receive another fitting and this is what I’m calling the hub) with some kind of fabric wrapped around it and then about 1/4″ thick solder is added. It took me ages to get the pipe out. I want to replace that galv. pipe with plastic. It received waste from a bath and sink only, both of which are being replaced. It was just easier for me to change everything to plastic. The question is how do I connect my plastic to the cast iron hub? I
went to a plumbing suppliers and posed the question to them. He got three gaskets of different sizes and I bought the one that I thought would fit – the middle size. The bigger one was bigger than the O.D. of the hub. It’s a Serco 2″ Service Multi-tite. This fits inside the hub reasonably snug but there’s no resistance to pulling it out. A 1.5″ dia. plastic pipe fits in the hole in the middle of this thing, again there is no resistance to sliding the pipe in and out.
Is this gasket the right size? The plumbing shop said to use 2″ dia. plastic pipe. Is it the case that the 2″ pipe will expand the gasket so that there is a tight fit between itself and the hub? If so and I do have the right piece, what’s the best way to fit it? Put the gasket in the hub and then force the plastic pipe through the hole? This seems a lot easier than pushing the pipe through the gasket and then fitting it all into the hub. I appreciate any replies and sorry for rambling.
David

PS. We haven’t been able to shower in the house for about 5
weeks now. Next time I’ll hire it out.