Plumbing would be a hassle. Getting water up there to flush toilets, etc.
That’s true as well.
Plumbing would be a hassle.
It is done in stages, an approx half a pound of pressure per foot of elevation.
5280/2= 2640 PSI, a bit too much for your drinking fountain!
Also, the waste pipes make a 90-degree offset every so often, to prevent noise... would not want the pipes to crack if something solid was flushed.
You would have to have reservoirs within the building. Essentially, a built in water tower.