Proper grounding

[fharris770]

I'm looking at the wiring of a house I may purchase.  House has two 150 amp panels.  I see a ground entering one of the panels from the copper cold water line of a hot water heater adjacent to the panels.  I don't see a ground running to second panel (haven't taken the covers off).  Water piping throughout the house is copper and the main supply line entering the house is copper.  Only problem is I know at some point underground the copper transitions to PVC as that is what is at the water meter.

How do I verify the house is grounded properly?  I have used a circuit tester at outlets and every one I have checked shows proper grounding.  Also, house is about 20 years old.  Do I assume the copper water supply line was "grounded" outside the house before the foundation was back filled?

[JP]

What is considered proper grounding today and what was considered proper grounding 20 years ago are very different. Without getting into a complicated ground potential discussion, I would say that it would most likely not meet the current 2008 code. 

[fharris770]

so, can you give me your thoughts on what should be done to bring up to current code, please.

[fharris770]

OK, so I did a little more inspection on my own.  When looking at the Meter Box there are two main feeds entering from the street (one for each 150 amp service panel).  There is also a large sheathed copper wire that disappears into the ground.  I'm assuming this is the primary ground.  Upon going back inside I can observe two very large sheathed lines traveling from the meter box to the service panels.  Upon removing the cover from one of the service panels I can see that the sheathed cable contained two very large black sheathed cables consisting of stranded aluminum.  Also in the sheath were surrounding strands of aluminum.  One main cable goes to each bus of the panel.  the "loose" strands of aluminum are gathered, twisted and attached to the ground/neutral bar with a heavy duty lug. 

So now I know that the panels are grounded well!  I still don't know why a smaller (about 6awg) bare copper wire is running from the ground/neutral bar to the water heater cold water line (copper).  But at least I know that is not what is grounding the electrical system.

[JP]

A 6g or a 4g in updated electrical systems is normal for grounding. Check out this page http://www.wireityourself.com/electrical_service.html it will answer some questions.