This model shows a simplified principle, which is also found in most toilets. When water is slowly filled, the water level slowly rises. This could be used for the seat height of a chair. As soon as the water level reaches a certain height, the tank „flushes“ everything out and the water level, i.e. the seat height, drops enormously. A pump could slowly fill the flushed out water back into the tank and the rythm „slowly up and fast down“ starts again.