All of the plumbing is plastic here so the water line does not really figure into it.
My ground electrode is very robust tho. I have several rods and a lot of Ufer, not the least of which is a 15,000 gallon swimming pool.
Combined voltage drop in the neutrals has to go somewhere. I bet that if I strung a wire across the canal and checked the neutral at my neighbor's house there would be a very significant voltage difference and the "ground" would be different too.
