Chris Lewis wrote:

According to Tom Horne :


250.50 Grounding Electrode System.

...

250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe.


....


There is no way you can read NEC section 250-50 that allows you to avoid
using the underground metal water piping as part of the grounding
electrode system.


Actually, one can show that very easily: note (A) above:

"Electrodes PERMITTED for Grounding".

Emphasis added.

It doesn't say it's "REQUIRED if present" for use as a grounding conductor.

It says it _can_ be used as a grounding conductor (and elsewhere says if used
it needs to be supplemented).

Elsewhere in the code it goes on to say that such pipes MUST be grounded.

Which means in the end it doesn't matter, because it's going to _act_ as
a grounding electrode, whether the NEC thinks of it as that or not.

This whole argument is silly - it doesn't matter which way, because it's
going to be grounded (and in intimate earth contact giving decent duty
as an electrode) ANYWAY.

W Tom's position is that you can forgo connecting to an underground
metal water pipe if you have another electrode. Did you read the first
section of the US NEC that I quoted? It says
"250.50 Grounding Electrode System.
If available on the premises at each building or structure served,
each item in 250.52(A)(1) through (A)(6) shall be bonded together to
form the grounding electrode system. Where none of these electrodes
are available, one or more of the electrodes specified in 250.52(A)(4)
through (A)(7) shall be installed and used. "
Note the use of the prescriptive SHALL in the first sentence. If the
water pipe is there you must use it as part of the grounding electrode
system. That remains true even when there is no other metallic piping
present. Surely you are not saying that the underground metal water
pipe in a building with no interior metallic piping is "likely to become
energized" thus falling under the bonding requirement.
--
Tom