Experience
Experience
I agree. but I don't know what that means.
Please explain. I don't understand.
I don't know, but it seems to me that the well casing would be the primary grounding electrode and any ground rod would be supplemental, requiring at least a #6 to the well .... if the well casing would be connected to metallic waterpipe more than 10 ft long would require a GEC sized according to table 250.66.
Unless you do this for a living and have good reason to deviate from an EGC, the questions asked are understandable. In some instances the well casing, under code within a structure would require a grounding electrode.
In the instance of discussing a rural domestic water well system, the primary function of a metal well casing must be bonded as an Equipment Grounding device. The case EGC bonding prevents any ungrounded shorting to the casing causing a continuous energized and fatal potential that does not trip the well motor feed OCPD. An non-grounded Ground Electrode will not protect equipment from the case fault condition. A PVC casing and well polytube does have an advantage in this instance.
Secondarily, you may consider the metal casing a Ground Electrode for lightning dissipation should surrounding equipment be protected from being a lightning beacon...do not expect guarantees on this aspect.
On a practicality note, using a metal casing is no longer common for modern well installs for both handling, water purity and electrolysis reasons that this discussion does not entail. There are probably special conditions that may exist such as geothermal environs that may require metal casings, but that is another subject.