A Practical Guide to Inspecting Plumbing Vol.4
A home had been closed up for the winter and the  water heater emptied.  The home-owner came back to de-winterize the  home.  He fired up the electric water heater before it had a chance to  completely refill with water it still had lots of air in it.  When he  turned it on, the top element exploded and blew right out of the tank.