Thank you for your replies all of you
It means a possible amount of up to 1.5 tons to carry on and keep at a positive temperature during the flight.
Might be even heavier on Emirates A 380, "offering" in flight shower possibilities ...
I guess the "potable" water means "pure water", not drinkable either than heated for hot bewerages; otherwise when and how were the tanks desinfected ?
The cabin air is filtered, same for the water with carbon filters ?
Sorry to be so curious and picky
