You are confusing an underground water pipe replaced in
plastic with something different from what I am discussing.
Plumbers sometimes replace *interior* copper water pipes with
plastic. That would make the bathtub 'hot' if wall receptacle
was safety grounded to cold water pipe that was 'fixed' by the
plumber.

Again, earth ground has nothing to do with the earthing
electrode. They serve different functions. But dumping
electricity into a household cold water pipe system - pipes
inside the house - is unacceptable today because interior
pipes are replaced in plastic.

BTW, in one jurisdiction, a dedicated 6 AWG ground wire
connects every steel bathtub directly to breaker box safety
ground. Same reasoning. The only connection to water pipes
is to remove electricity; not dump electricity into those
household pipes. This has nothing to do with the buried
utility water pipe.

HorneTD wrote:
It does not have to be what either of us believe is smart to be what is
required by law. If the US National Electric Code (NEC) is adopted by
reference as law in your location then you have to use any underground
metal water pipe that is three or more meters in length as part of the
grounding electrode system. It does not matter if in your or my opinion
that imperils someone in the shower or bath. You have never to my
knowledge accepted the point that whether the water piping in the
building is metallic does not effect the requirement to use that
underground metal water piping as a grounding electrode. That
underground metal water piping is for many homes the only effective
earth grounding electrode. I have been doing electrical work for nearly
forty years and I have never encountered a municipal water system with a
resistance to ground of more than twenty ohms. During that same time I
have never had a single or double driven rod electrode of ten feet per
rod or less measure less than fifty ohms. The best grounding electrode
is going to be the one that puts the most conductive surface in contact
with the earth at the deepest level. For many buildings that is the
metal service lateral of the water supply.
--
Tom H