Has anyone seen PEX being used as the drain line for the TPR valve. Is it OK to use in this location. I know PEX is good stuff and inspect it alot in new construction, but this is the first time I have run across it on the TPR. Also, the plumber used 3/4 inch PEX on the hot water drain pan coming off an inch fitting. Thoughts please
IRC 2803.6.2 says it’s okay, UPC 608.5 says no.
The drain-pan piping does not matter. It can be whatever is available. . .
I see it fairly often in new construction and it’s normally the Red on the TPV…
maybe they expect it might get Hot 
Thanks for the help.