250.52 describes when a metal underground water pipe is considered an electrode and requires it to be "electrically continuous (or made electrically continuous by binding around insulation joints or insulating pipe) to the point of connection of the grounding electrode conductor and bonding jumpers, if installed.
(There used to be a 5 ft limitation but I fail to see that in then '11 Code)
250.53(D) states if used as a grounding electrode the continuity of the metal underground water pipe shall not depend on water meters, filtering devices, and similar equipment .
As don states, I don't seen a valve specifically listed but an inspector might well look at it that way in light of the "similar equipment wording" especially if the valve is installed by an easily removable means such as unions.