Pressure filling loop valve replacement?

The pressure filling loop valve connecting to the hot water is leaking at the tap so I need to replace it. If I make sure that the filling loop is closed from the cold water end and disconnect the valve, presumably once the hot / warm water has drained out and I've replaced the valve I'm going to have a lot of air in the system. How do I bleed this excess air?

Eddie S.
December 2012