What is water pressure caused by?

Answer 1

In a typical municipal water system, water pressure is caused by gravity.

It works like this:

Water is stored in a reservoir which could be underground or above ground. From here it is pumped through a filtration and treatment system, then into tall water towers. From these towers it is gravity fed to the water mains under the street that supply water to the houses, shops and factories.

The reason for pumping the water to a tower first, and not directly to the mains, is to avoid fluctuations in pressure during periods of high and low usage.

In a rural or cottage system, there is often no buffer tank, so the pressure fluctuates up and down constantly as you use the taps.