Hello! I would like to add a 2" waste line (with appropriate venting so not to "wet" vent) for a new washer located a couple of feet from the main waste stack in my 60 year old house. The waste stack is 4" cast with a cast c.o. tee and threaded brass c.o. plug just above the concrete floor. After this arrangement the waste stack turns into 4" copper. I was thinking if there was a chance of removing the threaded plug, threading a 4" male adapter (?) into the clean out hole and then putting a 4" PVC tee wye onto this with a new 4" PVC clean out plug and a 4 X 2 reducer bushing to accept my new 2" waste line.
HOWEVER, I found that the nominal 4" brass plug is actually 4" in diameter and not 4.375" (thread diameter) as I had anticipated. Soooooo, it seems that a typical 4" PVC adaptor (with 4.375" diameter across the threads) will not fit into a 4" exactly hole - at least not without magic shrink compound.
I have searched the net in my own feeble way in search of either a threaded reducing bushing (exact 4" OD to 3" FPT) to fit a 3" adapter and tee wye into the system with a 3" clean out plug and 3 X 2" reducer bushing - but, cannot find anything true 4" exact OD to adapt to the existing hole. I'm thinking there must be a simple solution out there but, so far, it has evaded me.
What are my options or what have I missed in readily available plumbing fittings?
bbB