When water is poured into a U-shaped water-hose, the water reaches the same height on both sides. This result is generally expected. Now the hose is wound up a few times around a reel. Water is poured into one end of the hose. Observe how the water level is different on both sides.
Explanation 1: . Think about that and you will understand how you can pour tea out of a teapot! When the pot is tilted sufficiently, the level of the tea in the nozzle exceeds the edge of the nozzle. Then the tea is poured out.
The wound-up hose forms no real communicating system, because some air is locked in.
Explanation 2: According to the law of the 'communicating vessels' the levels in both legs of the U-shaped water-hose are the same. The water has free contact between the two vessels, and the same (atmospheric) pressure is exerted on both surfaces of the water.
When water is poured into the wound-up hose, this law of 'communicating vessels' will hold for as much as the first half loop of the hose is completely filled with water. When more water is poured in, the water will flow over the highest point of the loop and it will settle at the bottom of the next loop. At this moment an amount of air is locked up in the second half of the loop. When more water is poured in, that amount of air is compressed. One needs more pressure (higher water-column) of the water that is poured in, to let the water pass the first loop. The same holds for the next loops.