All "metallic systems" in a home that are capable of being
	energized are required to be bonded to the grounding system.
	This is usually taken to mean:  metallic water supply, metallic
	drain-waste-vent pipe, metal ducting, gas lines, and sometimes
	metallic structural elements (eg: metal framing systems).

	The rationale for this is simple: if somehow a hot conductor contacts
	a water pipe, say, you don't want every plumbing fixture in your
	home to become live.  The bonding attempts to ensure that you have
	a low resistance path to the ground system at the panel, and thence
	to the neutral - ensuring that this ground fault is stopped by
	a breaker or fuse tripping.  Remember that this is independent of
	the grounding electrode system's conductivity.

	Normally the bonding of most of these systems are done by the
	equipment involved.  Furnace ducting is grounded by the furnace
	connection.  Gas line grounding is done by the gas man ;-)
	So we'll mainly talk about water line grounding here.

	The NEC appears to insist that each electrically isolated section
	of metallic water pipe must be jumpered together.  Take particular
	note that you are required to provide a jumper wire that bypasses the
	main water meter (especially if you're using the water supply line
	as a grounding electrode), and a jumper between hot and cold if the
	water heater is an electrical insulator.  The CEC, for example,
	also requires that the frame of your clothes washer is bonded to the
	cold water supply pipe.

	Exact details of how this bonding should be done is beyond the scope of
	this FAQ.  It tends to be a 6ga wire running from the grounding terminal
	of the panel to a convenient copper pipe.  If the water supply is used
	as a grounding electrode, the rules become stricter (5' rule applies
	in NEC etc.)

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