electricj: We are required to run all the grounding conducctors to the disconnect. For 100 amp service I use a no. 6 bare copper and all it has to do is follow the contour of the building. In fact for any ground rod use no.6, this is in the code. To the water line thats different No.6 for 100 and 150 amp service and No.4 for a 200 amp service, etc And of course bury the ground rods spaced at least 6 feet apart.
