I have a problem with any test that occurs on the actual continuity of a given run of conduit, especially when it is going to be used as an essential conductor that could be asked to carry large currents, under fault conditions.
Reason I say that is, because that test only gives a "snap-shot" of the condition of that conduit run at that given time, not 1 or 5 years down the track.
This resistance will change over time.
I would never fail to run a new (seperate) ground back to the supplying panel.
