The season has a lot to do with how much we use. But as far as refills, our rack holds a #1 gallon tank but we fill it ourselves with a larger fiberglass
unit. If we run into a place where they only have exchange, we take the tank and transfer into our tank ...
Its easy and safe to transfer with the right fittings.. you conect both tanks
with a.common hose, turn the full tank upside down and set it higher than the empty tank, open both and let set. The fluid will drain into the lower tank. Very common to carry multiple fittings as different countries used different conections. Even in the US there are two, an old style screwing inside and new version using a plastic knob on the outside..