Pex as a TPR tube

[Rebecca Davis]

Checking in here for some feed back. I have found this code relating to pex as a TPR tube. However a property manager has asked around with several plumbers and all of them seem to believe that using 3/4 Pex with crimp connections is okay. I want to make sure I'm interpreting this correctly. Is this is requiring a one inch TPR tube?

P2804.6.1- Point 3 and 14 are relevant.
3. Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap.

14. Be one nominal size larger than the size of the relief-valve outlet, where the relief valve discharge piping is installed with insert fittings. The outlet end of such tubing shall be fastened in place.

If using PEX, the pipe must be one nominal size larger than the size of the relief-valve outlet, where the relief valve discharge piping is installed with insert fittings. The outlet end of such tubing shall be fastened in place.

 

[BN4537]

You are reading it correctly. 3/4" PEX with crimp fittings is not OK for a water heater discharge pipe.

I would be OK with expansion PEX fittings (erroneously called PEX A, you can expand PEX A or PEX B as long as it is listed to ASTM 1960, which most PEX B is anymore) because they do not reduce the pipe diameter. They are still insert fittings, so one could argue they don't meet the code either, but I am OK with it. The caveat would be that it is even more important to fasten the end in place with expansion fittings because they will rotate much more freely than crimp fittings.