What Is A Float Type Air Vent Valve?FFloat Type Air vent valve is a kind of valve to vent troublesome air from hydronic heating systems. It is commonly used for air release in plumbing heating system and installed at the highest point of the system and is often seen on radiators, manifold and water separators. loat Type Air vent valve is a kind of valve to vent troublesome air from hydronic heating systems. It is commonly used for air release in plumbing heating system and installed at the highest point of the system and is often seen on radiators, manifold and water s