When there is gas in the system, the gas will climb up the pipe and eventually gather at the highest point of the system. The exhaust valve is usually installed at the highest point of the system. When the gas enters the exhaust valve, the valve chamber gathers at the exhaust valve. In the upper part, as the gas in the valve increases, the pressure rises. When the gas pressure is greater than the system pressure, the gas will lower the water surface in the chamber, and the float will fall with the water level to open the exhaust port; after the gas is exhausted, the water level rises and the float also Then rise and close the exhaust port. By the same token, when a negative pressure is generated in the system, the water surface in the valve chamber drops and the exhaust port opens. Since the external atmospheric pressure is greater than the system pressure at this time, the atmosphere enters the system through the exhaust port to prevent the danger of negative pressure. If the bonnet on the exhaust valve body is tightened, the exhaust valve stops venting. Normally, the bonnet should be open. The exhaust valve can also be used with the block valve to facilitate the maintenance of the exhaust valve.