On Sat, 11 Oct 2014 10:42:27 -0700 (PDT), John G
wrote:

On Saturday, October 11, 2014 10:00:19 AM UTC-4, Robert Green wrote:
wrote in message

wrote:



In that case the ground wire did NOT go back to the panel, but to a

clamp on a cold water pipe.



Until the 70s that was legal.



But stupid. And that's why they outlawed the practice. The wire went off

to parts unknown (in my case) and some small amount of current leakage

apparently caused galvanic corrosion to occur where it was clamped to the

waterpipe. It caused a pinhole leaked to develop. All tucked away behind a

stapled ceiling and hard to find without making a hell of a mess. I would

not even had known about it until I took the ceiling down (revealing all

sorts of other nasty surprises). I am sure the previous owner installed

that stapled up ceiling to keep those sorts of issues from the eyes of a

good home inspector.



It was also far enough away from the service entrance that a replacement of

a section of copper with plastic where it entered the house would have

broken the connection to ground.



In my mind, those are two good reasons why they changed the code and why

such connections should be removed and done according to modern rules

whenever they are discovered even if they are still grandfathered.



As for the OP, what was legal in the 70's is moot.



--

Bobby G.

*Actually the 2014 code does still permit the connection to the waterpipe. Article 250.130(C)(1) states that is is permitted "At any accessible point on the grounding electrode system as described in 250.50". The waterpipe is part of the grounding electrode system. The water meter and water heater bonding jumpers would have to be in place and the clamp would need to be approved for the type of metal piping.

That is what I think happened in your case. The disimilar metals of the ground clamp (Brass) attached to a steel pipe acted as a battery. Just like a water heater. The clamp should not have been buried in a finished ceiling. The ground wire should have been run over to the water meter location where it would have been accessible and could have been clamped to the water pipe or the grounding electrode conductor.
By code NO electrical connection is allowed to be "concealed". Ground
or otherwise, they must be "accessible" - and above a stapled ceiling
does not comply.