When you need to exhaust the gas pipeline, should be anti-clockwise rotating stem ,make stem with the valve up, so that the air inside the tubes get into the body under the pressure of water , and discharged from the exhaust nozzle, with  the water pipe filled with body cavity, so that the buoyancy float in the water under the action of moving up to plug the exhaust nozzle to achieve self-sealing, pipe in the normal line, the water pressure under the action of the air continuously into the exhaust the upper part of the valve body cavity, forcing float down, leaving the original sealing position, when the air and from the exhaust nozzle discharge, with the attendant, then float back to the original location a self-sealing, therefore,

Normally exhaust valve is always open, and the float repeated the above-mentioned moves, air is discharged, when is needed for repairing or cleaning the body cavity, valve should be closed. The exhaust valve, valve stem clockwise rotation is closed.