How to remove PVC nut sandwich

Question

Pictured below is the drain for a tub that I need to take apart (to fish out a rubber drain stopper that fell down).

I don't understand what was done in the PVC area (or what these things are (called)) and how to undo it so that I can take it apart.

What should I loosen to undo this and in what order? It seems like PN.a and PN.b are in eachother's way and neither can be loosened.

Is it likely that there is a pipe between PN.a and PN.b that I cannot see and both of these nuts are slip fittings over that pipe? (This is a clawfoot tub to it's possible they lowered it)

CP.a and CP.b slip into CT.a and I cannot simply undo CN.a and CN.b and remove them (as it's not a union joint).

Appreciate any help.

Answer 1

All the nuts should be slip fittings, though PN.a is odd, and may actually be capturing the end of a flanged-end slip tube stuck into PN.b - usually on a plastic drain tee that's just a slip-tube extension of the tee, but given a metal drain tee it might well be different. Image search appears to confirm that likely difference.

You have to remove the overflow and drain shoe (the "tub ends" of CP.a and CP.b) to get freedom to move things for further disassembly. That involves unscrewing parts inside the tub. Then you loosen CN.a and CN.b and those parts can be pulled out (which may be all you need to get your stopper) at which pont you are free to rotate and pull on the drain tee to get it to come up from where it's slipped into PN.b (which you may loosen with an adequately sized wrench, leaving PN.a alone, but letting it be pushed by PN.b if it's jammed tightly.)