SCAR sewage vent valve for a round barrel-shaped, stainless steel float valve trim including, valves and valve impeach. The valve is installed at the pump outlet or water distribution pipelines, to exclude the accumulated air in the tube, in order to improve the efficiency of the pipeline and the pump, when the negative pressure is generated within the tube once the elbow, the valve quickly sucked outside air, in order to prevent the pipeline damage due to the negative pressure. When the water injection tube, the valve is in the open position, a large number of exhaust gas, when the air is drained, the valve is filled with water, the float rises and driven valve closed to stop the exhaust gas, when the normal inner pipe for conveying water, if a small amount of air in the valve gather meat to a considerable extent, the water level dropped valve, when air is discharged from the hole. When the pump stops, generating a negative pressure within the flow of water in case of an empty tube or pipe, then quickly turned plugs, intake air to ensure pipeline safety. Medium temperature: 0-80 ℃.