Originally Posted by
weero
Do the toilets need water to be considered operational?
No they do not. Bottled water and hand sanitiser are used whenever there is an issue with the toilet faucets or potable water. The vacuum system will still continue to work, and even if the vacuum blower is unserviceable, above 16,000 ft the laws of physics will ensure the ability to clear the wreckage of one’s constitution.
It isn’t very common at all to run out of potable water, but it is always a possibility. More likely is the odd failure of pumps etc occurring inflight.
Demand must have been high on the OP’s flight.