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wrote:
I do not know exactly what the code says, but I do know what makes sense
from a safety perspective. The neutrals of all circuits should be
connected to ground at ONLY one place - in your main service panel. There
must be no grounding of neutrals in sub panels. Ranges etc. connected to
sub panel circuts should use a 4 pin connector (hot, hot, neutral, ground).

The ground wire from your main panel may be connected to multiple grounds
and it's best if these are close together. Two grounding rods are
frequently used for a lower resistance ground path and better reliability.

Do not ever use a pipe as a ground. The water supply line may be PVC or
may be changed to PVC at some time in the future and you would have no
ground.

Since a good ground is so important, use the gauge wire required by code or
larger, protect it where required and never allow a splice in it. Use only
the best quality U/L approved grounding clamps and be sure all contacting
surfaces are clean and tight.

All of this applies to your generator too. For best safety, if your
generator is outside, it should be physically close to your system ground.

If the code requires anything less, it should be changed.

The US NEC requires that any underground water piping that is ten feet
or more in length shall be used as a grounding electrode. That is not
optional. No matter how authoritative a posting recomending against
this sounds it is bad advice for anyone who's work is governed by the US
NEC.

If the underground water piping were too short or non conductive the
code would require that any interior metal water piping that is likely
to become energized be bonded to the service equipment enclosure, the
grounded conductor at the service, the grounding electrode conductor
where of sufficient size, or to the one or more grounding electrodes
used. That connection is required regardless of whether there is any
underground metal water piping present. Most Authorities Having
Jurisdiction (AHJs) consider any metallic water piping that supplies
water to any electric appliance as likely to become energized and
although most AHJs will except the Equipment Grounding Conductor (EGC)
of the electrical equipment attached to the piping as the bonding means
for interior gas piping they will not except an EGC as the bonding means
for water piping. For water piping the bonding conductor must comply
with 250.104 of the US NEC which requires it to be sized exactly the
same as an Grounding Electrode Conductor (GEC).

[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.

250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in
direct contact with the earth for 3.0 m (10 ft) or more (including any
metal well casing effectively bonded to the pipe) and electrically
continuous (or made electrically continuous by bonding around insulating
joints or insulating pipe) to the points of connection of the grounding
electrode conductor and the bonding conductors. Interior metal water
piping located more than 1.52 m (5 ft) from the point of entrance to the
building shall not be used as a part of the grounding electrode system
or as a conductor to interconnect electrodes that are part of the
grounding electrode system.

250.104 Bonding of Piping Systems and Exposed Structural Steel.
(A) Metal Water Piping. The metal water piping system shall be bonded as
required in (1), (2), (3), or (4) of this section. The bonding jumper(s)
shall be installed in accordance with 250.64(A), (B), and (E). The
points of attachment of the bonding jumper(s) shall be accessible.
(1) General. Metal water piping system(s) installed in or attached to a
building or structure shall be bonded to the service equipment
enclosure, the grounded conductor at the service, the grounding
electrode conductor where of sufficient size, or to the one or more
grounding electrodes used. The bonding jumper(s) shall be sized in
accordance with Table 250.66 except as permitted in 250.104(A)(2) and
(A)(3).] Copyright 2002 the National Fire Protection Association.

Failure to follow the electrical code that is enforced as law in your
area can void your fire and liabilty insurance if that failure results
in an otherwise insured loss. It is considered a legal obsurdity to
attempt to insure against the cosequences of the insureds own unlawful
act. Insurance contracts are "contracts of utmost good faith." That
means that all parties to the contract must scrupulously obey the law in
all matters that could affect any other party to that contract. To fail
to do so allows the other party to walk away from their obligation under
that contract if the failure to obey the law was the proximate cause of
the loss.
--
Tom H