In article , AZ Nomad wrote:
On Mon, 31 Jul 2006 23:22:14 GMT, Doug Miller wrote:


In article , AZ Nomad
wrote:
On Mon, 31 Jul 2006 19:33:04 GMT, Doug Miller wrote:


In article . com, "Brad"
wrote:
Both pipes should be at the same electric potential (ground) since
they are both are buried.
The grounding is done to help ensure the electrical panel has a true
ground.

Wrong, wrong, wrong, wrong.

The water piping is bonded to the electrical ground in order to insure that
the _water_piping_ has a true electrical ground -- IOW, to prevent the water

piping from becoming live in the event of an electrical fault somewhere.

The first poster had it right. The water piping is already at ground because
it is in direct contact with the ground. Unless of course you have
your water brought to you on pipes suspended in the air. Or perhaps you
have it flown in?

No, he didn't. The electrical system has its own, *separate* grounding
electrode. Metal water piping is bonded to the electrical system grounding
electrodes to ensure that the metal water piping cannot become live, *not* to
provide a ground for the electrical system.

Metal water piping burried in the ground cannot become live.
It is as well grounded as possible. If you connect the house's ground to
it then it is in order to keep the house's ground from being live
compared to the water pipe.

This is *not* correct in any respect.

There is no guarantee that the electrical system's grounding electrode, and
the metal water piping, are at the same potential unless they are bonded
together -- despite both of them being buried in the ground. Electrical
resistance in the earth is not constant, and in fact can vary widely even over
short distances.

I repeat: the *sole* reason for bonding metal water piping to the electrical
system's grounding electrode(s) is to ensure that the water piping is at the
same potential as the electrical system's ground, so that the water pipes
cannot become live in the event of an electrical fault.

Google is your friend, and educating yourself on this topic should be easy.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.