The water that is used initially to fill a hot water heating system contains dissolved air. Make-up water subsequent added will similarly have a high air content. Heating this water releases the air and permits it to be circulated in the system, for which it must be vented. The purpose of the Air Purgers is to continuously separate and collect any air from the water as it circulates so that it may be vented automatically by afloat air vent without the necessity for frequent manual venting.