When the water in the pipe starts to fill, the plug head stays in the open position for a large amount of exhaust. When the air is exhausted, water accumulates in the valve, and the floating ball is lifted. The plug head is driven to the closed position to stop a large amount of exhaust. When the water in the pipe is transported normally, if a small amount of air accumulates in the valve to a considerable extent, the water level in the valve drops, and the floating ball also drops. At this time, the air is discharged from the small hole. When the water pump stops, When the water flow inside the pipe is empty or negative pressure is generated inside the pipe, the plug head quickly opens to suck in air, ensuring that the pipeline is complete.