Just go to Menards and look at the PEX tubing they have there. The pressure and temps are printed right on the PEX tubing. The Pressure does decrease as temp rises. When it is cold it withstands more pressure. If one were to bury it below the frost line, the temp would be approx 50 to 58 degrees. Well below any temp rating given. That being said, it will withstand 125 psi just fine. When placing PEX for radiant floors, it is pressurized to 100 to 125 lbs for 24 hours for testing before pouring concrete.
