Plumbing Questions? Ask a Plumbing Expert.
Given the age of your heater there's a high probability that the tank has failed. It's possible but not likely that the leak is coming from the drain although it's not uncommon for the tank weld around the threaded drain tapping to leak (this can't be fixed anymore than any other tank leak). You'll have to cut away any plastic collar around the outside of the drain then pull the tank insulation away from where the drain screws into the tank to verify your theory.