Removing Galvanized from Cast Iron . . . What are my odds of success?

[Hip2u77]

Update: I got impatient and grabbed my 24" pipe wrench and it started unscrewing before I could even lean into it. Of course, a very small part of the thread either broke or rusted away. I was able to get a male adapter to start and turn maybe 3/4 - 1 full turn. I would assume I need to hunt down a 1-1/2" pipe tap now? And speaking of pipe . . . the removed pipe looked a lot better than I thought it did. I think it would have been fine to use. Hindsight, amirite?


Original:

Happy Thanksgiving everyone! For my turkey day, I have to fix a bathroom sink drain before I can reset the only toilet in our house.

Strange question here. Is it possible to tell by pictures if my chances of removing the galvanized stub from the cast iron is decent or prone to fail? (Or if it's clean enough to use "as is") The inside looks like hell, but the outside seems solid and in good shape. I've got it soaking with a 3 part penetrating solution of PB Blaster, Loosey Goosey and WD40's rust penetrant.



The long story, if it helps. The bathroom wall drain hasn't been used since '99. After I bought the house in '98 I got tired of the slow drain, so I drilled a hole through the floor, ran an S-trap off the sink drain to a 90 in the basement and tied that into the main drain. I've got an unfinished basement, so it was quick to do and has worked fine for 20 years now.

A couple weeks ago I decided to replace the vanity and floor and wanted to start using a wall drain again. (I also read that S-traps were not to code.) Last week I tried a spade on a drain auger and got exactly 2" before hitting a solid rust clog. Today, I opened the wall, cut out the galvanized and planned on using a no hub coupling with a couple of extra hose clamps to go from the galvanized to PVC but I'm worried the inside of the pipe might be too rough and will just get clogged in a short amount of time. Kind of at a standstill trying to figure out if I should use the coupling or try to remove the stub piece.

 

[ImOld]

You need to remove every trace of galvanized in your home.

End of story.

 

[Sponsor]

 

[Terry]

You may want to run a tap for the lav drain into the cast, unless somehow you can pick out the remaining bits with a flat blade screwdriver
For the water lines, it's best to replace all of it if you can.

 

[Hip2u77]

Thanks for the replies. A friend had a tap which bit into the broke off piece and I was able to easily spin it out with the tap. The threads looked really good. I've got a temp setup in there now with a p-trap to block the odors and check for leaks. The weird thing is, last night it seemed like we were getting a slight sewer gas smell out of our kitchen drain which is the highest drain and first thing on that whole line.

That bathroom drain line was the only galvanized left in the house, which is a '56 ranch with one bathroom. The toilet drain and main stack in the basement (and vent) are still cast but everything else was changed to PVC (along with copper water lines) before '78 when we moved in.

Thanks again!