Avlufting

Avlufting is the process of removing trapped air from a closed liquid-carrying system to restore proper flow and operation. Air pockets in pipes, radiators, or equipment can hinder circulation, reduce heat transfer, cause noise, and lead to pump cavitation or flow disturbances. The term is commonly used in heating, cooling, and industrial systems to describe both manual and automatic venting actions.

The procedure is typically applied in hydronic heating systems, solar thermal circuits, cooling loops, and various industrial pipelines. In residential settings, avlufting is most often performed on radiators where air often collects at high points. In larger systems, automatic air vents may continuously release small amounts of air, while manual vents are opened at specific points during maintenance.

Common methods involve locating air release points at high points in the system, isolating and depressurizing the relevant section if needed, and opening the vent valve until water flows steadily without spurts of air. After air has been expelled, the valve is closed and the system is re-pressurized to its normal operating pressure. The process should be performed with caution, preferably when the system is cool to avoid scalding and to prevent pressure-related hazards.

Indicators that avlufting is needed include gurgling sounds, cold spots on radiators, reduced overall system efficiency, or fluctuating pressure readings. Regular venting helps maintain efficient heat exchange, steady circulation, and quieter operation.

See also: bleeding (plumbing), air vent valve, venting.