The Potterton automatic air vent is a pressure protection mechanism in the central heating unit. It works by using floatation to release built-up air. As water flows through the heating and cooling system, a float within the automatic air vent opens or closes depending on the water level. If the system contains no air, the float will be pushed to the top and the vent will be closed until the water level drops.
Fits a number of Potterton boilers
Technical specification
Waist Sizeab15cf11gvTypeAutomatic Air VentSupplier Part Number10/18728Brand NamePotterton