From some posts here, apparently many homes continue to be grounded via the water line. Haven't done that here for ages, almost all of the plumbing is PEX, and even on older homes (like mine), enough modern repairs have been made with plastic that it has interrupted that ground path in many instances. Every new home I've been on for over twenty has been grounded to an 8' ground rod at the panel, and for quite a few years now, two 8' ground rods.
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L.