no cold water up stairs?

you need to force water backwards into the upstairs bath or basin. Make sure the cistern and sink are turned off if e.g using the basin.
You could fill the bath with some water from the hot tap (make sure the plug is in), and use a hand pump to pump water from the bath into the cold tap which must be open. This will force any air back to the large tank in the loft and it will bubble to the surface.
However I bet you haven't got a pump. In this case connect mains pressure from downstairs kitchen up to the first floor tap using a garden hose somehow and pray that the pressure is great enough to shift the air in the system. Try to maximise the mains pressure by opening the stop-cock/gate valve fully and don't flush downstairs toilets.

Jim
January 2011

its possible the tap rubbers could be stuck down on their seating,
only a strip down of the taps will tell.

wirecutterman
July 2009