Kitchen Sink into cast vent stack.
 

HI

Doing a Reno on a kitchen and it has 3" cast vent pipe/drain pipe and I need to tap into the existing kitchen drain point with ABS.

Before I go and put the pipe wrench to this puppy, anybody tell me whether it will unscrew or?

Looks like a union. Your going to need some heat or penetrant on that to get it to budge. Start by soaking the connection with PB-Blaster. If that doesn't do the trick, hit with MAPP gas and then try to unscrew it.

Thanks kok328

I take it that it is the 1 1/2 copper that will unscrew from the cast?

Maybe I a missing something but why not just use a no-hub connector with an ABS stub to transition? That will allow you to keep the existing undisturbed and make for a fast fix.

Am I missing something here?