Water towers -- how does water go up to the tank and then go the tap in the house?

Answer 1

There is a pumping station at the bottom of the tower (in a small block building, usually). At night when electricity is at its cheapest, the pump is turned on and pumps water up into the tank/tower from whatever source it is attached to (well, purified river water, etc.)

There are usually separate pipes to fill the tank/tower and to empty it toward your tap.

Gravity causes the water to flow down the tower/tank to water mains, which are further split into smaller water mains, like the one running under the middle of your street. A small (3/4"diameter) tap line takes water (still under pressure from gravity) from the street main into your house.

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Answer 2

The inlet pipe is at the top of the elevated water tank and the outlet pipe is at the bottom.
During winter, pumps are also used to keep the water moving in the distribution pipes so that it won't freeze.

Answer 3

It is a 'stored energy` system.
The water is pumped up into the tank. - (Energy input.)
It flows out by gravity. - (Energy returned.)
It's an easy way to maintain pressure at the taps.