Many inspectors in this area won't accept a capped pipe as part of the Grounding Electrode, because it may contain only trapped air.
And they do this, why??--It's the pipe that conducts electricity; water is actually a rather poor conductor. It conducts enough for the few milliamps it takes to kill someone in a bathroom accident, but not enough to seriously be considered as part of the grounding.
In fact, pure distilled water is actually a reasonably good insulator.
