We got no water at the moment as there is a leak on the mains in the street and our internal pipework ran at least partially empty. Our (rather new) Baxi 860 Combi is upstairs, probably amongst the highest points in the pipework. Is there anything I need to watch out for when restarting the boiler? Do I need to get air out of the water inlet (if so how?) before a call for hot water or is that not a problem?