Tub drain - galvanized waste/brass/PVC/I'm over my head

[mar504]

Looking for suggestions on how to handle this situation. We removed the old cast iron tub that's been in a bathroom for 50 years. The attached picture is the waste pipe, house is on a slab. I can't get that nut off the waste pipe, tried spraying lots of WD-40 and let it sit but did not help enough to get a turn on it. The awkward angle does not help, I'm using some channellocks to try and turn it but they are at an angle because the nut is below the slab.

I may not be able to get the nut off the pipe, if that's the case, what's my next step?
And if I do get it off, at least the PVC drain kit leaves a slight gap going into that drain... will I need a no-hub coupling?
A brass kit was there before, any advantage to that over PVC?

 

[mar504]

Another view of the drain... so, yeah, its pretty much welded together with rust and corrosion, no way its coming off unless I cut it off somehow.

 

[Sponsor]

 

[Jadnashua]

WD40 isn't that great for this application. Something like PBlaster may work, but you may need a bigger wrench. See what one of the pros has to say.

 

[Standardairconditioner]

No liquid will work on that frozen nut.

No amount of torque will turn that nut. You'll be turning the entire pipe before the nut gives from it.

Cut a gap in the nut, but not deep enough to the threads. Get a pry bay into the gap you cut, to widen the nut away from the threads. Several gaps cut around the nut may be necessary.

 

[mar504]

Thanks guys! Cutting the nut off worked well, I did manage to damage the top 2 threads however. May not matter, the threads below it are corroded to hell, I'd either need to use a giant gasket or another solution. Can I use one of those fernco couplings to transition from the old pipe to PVC? It may be on part of the threads of the old galvanized pipe, is this going to be a problem?

 

[Jadnashua]

It depends on the OD of the pipe. They make a variety of banded couplers, but not for all types of pipe.

 

[Standardairconditioner]

Thanks guys! Cutting the nut off worked well, I did manage to damage the top 2 threads however.

Don't worry about it.

Can I use one of those fernco couplings to transition from the old pipe to PVC?

Yes.

It may be on part of the threads of the old galvanized pipe, is this going to be a problem?

No.