According to Takoma Park Volunteer Fire Department Postmaster :
w_tom wrote:
1) All connections to water pipes must be to remove
electricity from those pipes; never to dump electricity into
those pipes. Pipes are no longer acceptable as ground - earth
or safety. Connection to earth ground must be via dedicated
earth ground connector - and not via water pipes.

You have made this assertion before and I have pointed out before that,
in any jurisdiction that has adopted the US National Electric Code,
using an underground metal water pipe that is ten or more feet long as a
grounding electrode is required. Not connecting the grounded buss bar
in the service equipment to that water pipe is a violation of the law
that adopts the US NEC by reference.

It's not quite that simple - you're confusing the "removal" and "dumping"
bit ("grounding electrode" versus "grounded conductor" issues).

Both you and w_tom are right, except for your "using an underground ...
is required" bit.

For w_tom's "dumping electricity into the ground" bit:

Both the NEC and the CEC now frown on the use of underground metal pipe
as your _only_ grounding electrode.

Under some circumstances, the NEC will permit you to use a "10 foot or
more" section as a grounding electrode (if you can get a grounding strap
to within 5' of where it enters the ground, for example), but it
_usually_ requires you to add a second grounding rod.

This is because supply lines are often plastic or upgraded to plastic, and
even if they aren't, this can cause ground loops in interconnected plumbing
systems, conductivity may degrade due to corrosion, etc.

In other words, even if you do have a supply line meeting the "metallic,
10' underground" bit, it isn't _necessarily_ legal (let alone required)
to use it as a grounding electrode, and you must and/or can use alternate
means (eg: UFER, ground rod, grounding plate etc) as well/instead of.

For w_tom's "remove electricity from these pipes" bit:

In all cases, the CEC and NEC does require that metallic plumbing
MUST be interconnected to the electrical system ground so that the grounding
system can get electricity "off" the plumbing.

As a logical consequence, that 10' of underground metallic pipe that you've
interconnected to the system ground may _act_ as a grounding electrode, but
it may _not_ be considered a grounding electrode for the purposes of code
compliance.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.