Hi , is the air lock in a tap in the bathroom?.
If if is and you have a kitchen mixer, then open the airlocked tap, then open the hot side if the kitchen mixer , place your hand over the spout , followed by slowly opening the cold . as the mains cold is more powerful pressure , the idea is to force the cold mains water back upnthge hot pipe and out of the airlocks tap . if you manage to get water coming out of thge airlocked tap turn all taps off then force cold down the hot off the kitchen mixer again( without airlocks pipe open ) to clear any further air up and out into the cold water storage tank. Don't do this for a long time as you will be filling the storage tank up and it cwill eventually overflow.
Also try doing this with any other mixer taps if the problem remains