At my old home (built 1935) the electrical panel was not grounded. However, there was a 14 gauge copper wire connected from the Neutral Bus Bar to a galvanized cold water pipe. When we replaced all the old corroding galvanized pipe with Pex piping it was time to pound in an electrode.
The point is the ground you have today may not be a valid ground tomorrow.
I forgot to add the reason we changed to Pex piping was due to a serious water leak about one foot from the entry point into the basement. Rotor-Router came out and cut through the concrete path and discovered that the piping that connect from the water meter to the hose had been changed somewhere and it was Swing Pipe.
For those that don't know Swing Pipe is more commonly known as "Funny Pipe" and used for irrigation.
So basically the use of the Cold Water pipe as a Grounding source was insufficient. As the saying goes:
"You don't know, what you don't know."
