The two kettles contain a boiling aqueous solution. They must be cooled to room temp as fast as possible (otherwise adverse chemical reactions will take place). Only one pump and one cooling coil are available. It would seem the second kettle would fill up. However, would the increased "head" then allow more of the liquid from this kettle to flow to the tee, at the expense of the liquid from the first kettle? Thus equalizing the height of liquids in the two kettles.