A bunch of us were bored at lunch today and we started wondering, "Where does the water go when you wash your hands for flush a toilet on the 70th floor of a skyscraper?"

A google of the topic uncovered some cool technology that collects and actually treats and recycles water every few floors of a modern high-rise.

What about old school? From the top of the empire state building, I can see water getting pumped UP to supply different floors but simple math would tell you that a gallon of flushed water falling straight down 800 feet would blow out any pipe. Does the pipe spiral down? how many pipes are there? Do they put septic tanks in every 5 floors and treat/empty them every so often?

It's bugging me.

Another show-stopper seems to be, "why does the hotel maid always stop up the bathtub drain after she cleans it?" I can't find the answer to that one either.