Okey, here you can see four different frames of the operation:









I'll also show some calculations soon, as it is pretty easy to calculate the height it will reach. When you have a normal piston with water resting above it it absorbs the weight of the water, but in this case that does not happen, it will just use the hydrostatic pressure. Still, when the surface area of the output-pipe is smaller than the surface area of the water inside the tank we get a leverage we can use to push the water higher up. If the surface area was twice that of the output-pipe, we would not only get twice the height of the source pushing, but it would also had have to be added together with the height of the water being pushed up, thus at a ratio of 2:1 we'd get about three times as much height.

Naboo