Are you referring to an auto air vent?
If so, you may expect some water to escape as this device allows unwanted air to be removed from the system and of course some water is bound to expel, how much water exactly, very minor - no problem, constant - possible system flush required as valve may be sticking open.
If its obvious that water is escaping with air then the question to be raised is how air is constantly getting into the system.
What other problems are you having to have discovered this?
Robert, October 2010
