Where did you get this info?
Just wanting to know.
I’ve seen top mount tpr valves with a curved drain pipe which would not be a restriction like 90 degree elbo, is a 90 degree elbow ok?
Well,I’ve known this code/rule, but you can find it in the Code Check Plumbing third edition book or you can read about it here:
Yes, four 90’s max
Ok thank you
From what I gather so far, it is the manufacturer recommendation and not IRC or UPC.
But it sound correct to me…
Thanks
It could be, but that would require extra piping and drilling a hole. I would bet dimes to dollars it is not.
Many manufacturer’s call for it to be piped to a suitable drain or the exterior. 
Am new any tips or suggestions?
If TPR discharge can be outside as you have suggested then how can an air gap be in the same room without the water heater being outside too? #item no.2
Blow off leg??? Is that what you called it???
Learn proper terms.