I can't seem to find out how to connect to an old cast drain pipe for my bathroom sink drain. There is a 4" to 3" reducing branch y that had a broken piece coming out of the 3" part. I chiseled out the broken piece and now I am stuck. I found some rubber boot things at lowes that are supposed to go inside the 3" part, but the are like 3.5" and the opening on the cast is 3 1/8". So my question how do I connect to this cast drain with modern typed plumbing.

My only other option that I could think of, would be to by like a 4" or 5" Ferring rubber boot and go on the outside of the cast, but I don't think that is the best solution here.

Thank you to anyone that can tell me what I need to buy,

A plumbing noob,

Extendoplumber

Go to a plumbing supply house and ask for a 3" 'no caulk cast iron hub gasket'. You will need to bevel the edge of the PVC pipe and lube it with silicone caulk before inserting it.

Is that what you are talking about? If so it is 3/8" too big. That is the rubber insert I was referring to in my original post.

Thanks for the reply

Joe



Edited 2 times.

Is there a hub on the wye, that the broken piece came out of? If yes, I take it the lead and oakum are still in the hub and need to be removed, before the donut can be inserted.