I'm having an extension done, and need to move my existing solar cylinders. Currently I have solar tubes on the roof (scaffolding required to get to them!) so don't really want to have to touch them. Can I just drain it down, move the cylinders, and then connect all up again and refill? It'll take a day or two to move the cylinders and boiler and redo all the pipework, so was concerned about the tubes overheating? or do I need to get up there and cover them up?!