I want to put in an electric shower in my downstairs cloakroom which currently has a gravity fed cold supply from the tank in the loft. The shower I am looking to install needs a mains fed cold supply which I could do by disconnecting this pipework from the gravity tank and connecting the cold mains feed, in the airing cupboard, to the cloakroom via the same pipe work. This cold gravity feed from the tank only supplies bathroom toilets and sinks and will not interfere with the heating system or bath fill which have their own separate cold gravity feeds. Doing it this way means that I wouldn't have to lift floors to run new pipework from the mains. Is their any reason why I couldn't or shouldn't do this?