The filling unit is composed of the supporting parts, main liquid pipe, cylinders, filling pipes, valves, distributors, and control rings. When a bottle is lifted to the filling valve, the inspection device detects it and opens the air valve. CO₂ enters until the pressure inside the bottle equals that in the cylinder, then filling begins. As liquid fills the bottle, CO₂ is discharged back to the cylinder. When the liquid level reaches the pipe and the bottle pressure becomes higher than the cylinder, filling stops automatically. Finally, the valve closes to complete the process.