Water heater drain pipe

[foplumbing]

I use IPC
is there a code section that restricts routing the pipe underground and essentially making a p-trap with the exterior? The exterior outlet would, of course, be at a lower elevation

 

[GReynolds929]

IPC 504.6.(8)

https://codes.iccsafe.org/content/IPC2018/chapter-5-water-heaters

 

[foplumbing]

IPC 504.6.(8)

https://codes.iccsafe.org/content/IPC2018/chapter-5-water-heaters

ah, didn't consider the pipe to be a safety device so i overlooked it

is it the same for AC drain? Tried looking in the mechanical code