Using a 1/2" drive, a 6" extension and a socket (I needed an 1 1/16"), remove the large brass plug of the sacrificial anode.
Q. What size socket do I need to remove the anode rod.
A. 1 1/16 inch socket.
You may only need this large socket (e.g., 1 1/16 inch) once or twice per year to remove the water heater plug (and anode for inspection if it has one).