I flew LHR-DXB and DXB- LHR on the A380 in J last month. During both flights the water in the toilets ran out an hour or so before the destination.

Does the A380 have a centralised water supply system? And if so did the water run out because all the F pax decided to shower? I thought that each toilet had its own tank in most aircraft?

Ive also wondered if the water which is carried by aircraft varies as per load/ duration of flight ? As weight plays a significant role in fuel costs.