Toilet drain code for remodel

[browncow]

I'm have a toilet drain running in the ceiling of my kitchen, then into the exterior 2x4 kitchen wall. In this transition from horizontal to vertical, the 3" copper pipe has a long sweep (two 45s connected by a short straight section). This runs in front of the top plate of the wall. It protrudes into the room a few inches, but was covered by a builtin wall section (bulkhead?) above the kitchen cabinets.

Now we would like to remodel our kitchen and remove the bulkhead. A 3" copper drain pipe protruding into the room near the ceiling is less than ideal, so it would be good to know what our options are.

I understand that wider turns are better for drains.. . But are they required on a horizontal to vertical drop?

ideally for this kitchen remodel, I could cut through the top plate of the wall, and put a tighter 3" elbow through it.
Is that allowed? (I understand I might have to provide extra studs to shore up the framing)

If it matters, there is an elbow at the bottom of the wall (in the basement), where it runs horizontally for a bit before joining the main horizontal run.
There is another elbow in the ceiling before the pipe enters the wall at the top. It seems convoluted - but there are reasons (I think).

Help and education is very welcome.

 

[Terry]

From horizontal to vertical a medium 90 is fine.

 

[Sponsor]

 

[browncow]

Thank you very much! That's very good to know.

If I do this, I will completely destroy the top plate in that section (it's mostly cut-through already, but I would most likely finish the job). I believe this means I will need straps to hold the now-completely-severed top plate together.

About the strapping requirements: I could ask a structural engineer that I have working on some other bits of this remodel, or I could leave him alone just go all-out and get four 48" straps, and put one on each of the two top plates, on the interior and exterior (it will all be exposed for this remodel anyway).

Do you have any advice?

 

[browncow]

Also, should I be worried whether an inspector will approve work on a pipe in an exterior wall? I know there are prohibitions about plumbing in exterior walls, but I'm not sure if that applies to DWV, or just supply lines.
Also, I'd expect some small amount of leeway given that it's a remodel of an old house, but I might also expect to hear "if you touch it, it must be up to code"