Phil Allison wrote:
"Trevor Wilson"

**AFAIK, the US system is fundamentally different to ours.

** In the US and Canada - it is NOT permitted to link neutral and earth
or plumbing within a premises.

"*within* a premises". The neutral *is* "earthed" right outside
the home, typically. The Code goes to great lengths telling
you exactly *how* to earth the mains at the service entrance.

However, this ignores the fact that most residential wiring
is grandfathered into "acceptance". Previously, homes *were*
grounded through their "water main" (e.g., my parents home
has ground at the water meter).

So, you can encounter all sorts of different situations
here in the US (I've even worked on homes with knob & tube
wiring!)

See here under the heading "Regulations".

http://en.wikipedia.org/wiki/Earthing_system

The MEN system used here in Australia seems to be unique.

See last para on same page.