This system, often called a hydraulic ram, works by converting the potential energy of the falling water in the drive pipe into kinetic energy (velocity of the water). This kinetic energy is then transformed into pressure energy when the valve closes. This high pressure is finally used to lift a portion of the water to a height greater than the pond level by storing the energy temporarily as potential energy in compressed air. The conservation of mass is observed in the total amount of water, some of which flows out through the valve before it closes, while the remaining portion ends up in the water tower. The conservation of energy is illustrated by the continuous conversion of potential energy to kinetic energy, then to pressure energy, and then back to potential energy in the raised water and compressed air.