system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 what do water towers do and how do they work?
gpt
Engineer here! 

Water systems are driven by pressure, through either pumps or gravity. In places where there are hills, a RESERVOIR near the top of a hill will spurs the pressure through a water conveyance system to the lowest locations of the water conveyance district. (NYC gets its water from the catskill mountains, about 100 miles north)

In places without many hills, water is pumped to the top of a water tower that will feed the municipality with pressurized water (so it's an artificial hill that water will push down from to allow water to rise up to the second story bathroom of your house)

Water flows through big pipes, then smaller pipes as it branches through the city or town you live in. The water mains in residential streets vary from 4" to 24", or larger. The pipes in the street tend have valves to isolate them, and at the end of each dead end is typically a fire hydrant, both to help put off fires and to drain the water line from stagnant water.

To get to the house, two cocks (lol) are used; they are small valves that isolate your individual house from the main line. These are called curb stops and corporation stops. These can be opened or closed to allow water to flow into the house.

Any other water or storm drain questions?