Eigenvector wrote:
In my house I have a run of PEX tubing that runs right past, almost touching
in fact, the gas vent for the hot water heater. My concern is that the PEX
is in danger or melting or accelerated decay due to the heat. Is there some
way I can shield the PEX from the gas pipe, would there be a code or fire
reason why this particular section needs to be rerouted away from the
exhaust pipe?

Just to clarify the exhaust from the water heater would have traveled about
5 feet before reaching the point where it is near the PEX so I presume it
would have cooled down some.


I suggest that you touch that part of the exhaust
while the water heater is firing to see whether it
really is hot.

To answer your question, you if you put a piece of
thin aluminum like flashing between the exhaust
pipe and the PEX with just 1/8 to 1/4 inch space
between pipe and aluminum and between aluminum and
PEX that would end your heat problem. If you
don't have that much room, you could take aluminum
foil crush it (do not make neat folds) and place
that barrier between the pipe and the PEX.
Chances are essentially no heat would transfer to
the PEX. The real question is whether this is PEX
for hot water or PEX for cold water, since since
tubing for hot water needs to be designed for at
least 140 degrees and the exhaust pipe not even be
that high in temperature.

Of course, the real solution, if the exhaust pipe
actually gets hot, is to cut the PEX and insert a
short fitting to gain room. That would be about
$2 for the fitting and $6 for several steel bands
and $10 to rent the crimp tool for 2-4 hours.