We're a bit short of room with the start of a new family in a new home so pushing some junk into the loft seemed like a good idea. However most of the loft is taken up by a head tank which doesn't seem to be filling any purpose. The water inside seems to be stagnant. We've run a few taps upstairs and downstairs and these all seem to be connected directly to the mains. I would love to remove this but how do I know it is safe to do so?