An apartment residence has one service drop for two services. A 200A and a 100A.The 200A consists of a 200A outdoor disconnect with 2/0 SER cable serving a remote panel board. Its interior grounding terminal block ties its #6 CU to the two ground rods and the #4 Al to the home water piping system.
There is a #6 CU grounding electrode conductor from the 100A panel to this terminal block for connection to the existing ground rods. There is no separate connection for the home water piping system from the 100A panel. Can the connection for the ground rods also serve as the connection to the water piping system for the 100A panel?