I think your service entrance tube, assuming it is metal, is your "grounding electrode".
Normally all the pieces of a rigid conduit system, being screwed together, are considered bonded to one another. Chicago and a few other cities require conduit throughout for home wiring.
To qualify as a grounding electrode, a metal cold water pipe must be bare and buried for at least ten feet. Gas pipes do not qualify.
When something else is your grounding electrode, the plumbing system must be bonded to it using #6 copper wire. I think the wire can be clamped to the nearest point on that portion of conduit in line from the panel to the grounding electrode.
Except, when the water pipe qualifies as a grounding electrode itself, run a #4 copper wire to within 5' of where it exits the house if your electrical service is greater t han 100 amps.