peter wrote:
peter wrote:
When I stand right next to the water heater, I smell a little bit of
gas at certain height. If I move to 1 foot away, I no longer can
smell it.

....
The installer did not use any joint compound on these tube fittings, so they
leak a little. Instead, he overtightened the large nut, but that still
doesn't work.
....

Then you need to replace the fittings--joint compound is for _threaded_
pipe fittings where the threads make the seal, _not_ for tubing
fittings. In a tubing fitting (or a pipe union, as well) the seal is
the mating between the taper and the sleeve _not_ the threads at all.

Sounds like they tried to reuse an old fitting that has either corroded
enough to no longer have a precise matching or, in trying to make that
connection, overtightned and likely crushed the ferule.

The real solution is to replace the fittings if you have sufficient
length to get a fresh tubing end or the tubing and fittings if not.