PEX Pressure Rating
PEX is generally rated at 80 PSI for 200F:
Hydronic Heating Applications
- This appears to say that if pressure is less than 80 PSI, then a pressure regulator is not necessary- https://www.nachi.org/forum/f22/max-pressure-cross-linked-polyethylene-73346/.
- PEX appears to be compatible with standard P&T relief valves - . But this does not say whether the P&T valve can be connected directly to the PEX, or only upstream of it, prior to the PEX transition.
- This says not to use PEX for P&T valves as there is a chance the P&T valve will fail -