so, this is it.
That tub is actually connected to drainage, but has no means of water
input. In that huge black tank is lots of (freezing cold) water that
we use to pour down the toilet bowl to "flush" it. The bottom of the
tub doesn't really have any lacquer left, so it's not very
comfortable, or clean, to sit in, but it's still a nice place to get
clean and feeling clean always feels good!