Thankyou John, as a Plumber that wasn't the first thing I would have thought of but it makes a lot of sense. There must have been a rising & falling slip-joint to allow this to work, I wonder what sort of maintenance liability that was for the Gas & Water/ODM boys..?
I think water cranes were the responsibility of the civil engineers. Most water cranes had such rotating joints; one problem was that, even with minor leaks at the joint, the arm could freeze in cold weather in either the normal position, or worse still freeze in a position where it trapped the loco whose tanks or tender were being refilled and prevent it being used! Coal-fired braziers (often called 'fire devils') were placed next to such columns in cold weather in attempts to prevent such freezing.