Thank you to all that have replied so quickly.
To answer the questions posed, the house is a single family with a detached garage built about 12 years ago as a teardown/rebuild on the same foundation. As far as I'm aware at this time it has only one water line and one natural gas line coming into the house, both meters are outside. There is a power feed out to the garage but no water. It has a 200A service, no backup generator. It has a ground rod installed along with the water line and gas line ground paths all bonded to the service panel ground bus. The lot is rather small, with homes quite close on each side. The house has been purchased and they take occupancy in about 3 weeks. I can feel myself doing some additional measurements with different loading. One measurement I plan on is to measure the water line amperage when the main disconnect is off to see if there is any feedthrough from water utility and/or next door neighbors.
To add additional info, I attended the second contractor electrician's inspection ( a second opinion, as it were) of the grounding and watched his process for checking all the grounding/bonding. He only found a loose screw in the outside telephone's service entry box that was bonded to the GEC leading to the ground rod nearby. He also disconnected the GEC to the water line and looked for arcing initially, then measured the voltage differential ( only a few millivolts). He checked all the ground and neutral bus bonding screws and found none loose.
He warpped up the inspection declaring it one of the better grounded homes he's seen. We still measured 1.6 Amps at the water line entry. There were much different (fewer) set of appliances running at this visit vs. the first visit.
I fully understand the presence of current at this spot and know that readings can vary quite bit. I have to believe for this house, with significant loading turned on, over 20 Amp reading would not be good, a 10 Amp reading somewhat alarming, and maybe even 5 Amps cause for followup. All I hoped to get with this post was a rule of thumb, but it appears to depend a lot on the home's setup. I also plan to advise this home inspector.
I appreciate all the inputs, the forum has really impressed me.