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1) If the exterior ground rod does not exist, install two ground rods spaced a minimum of 6 feet apart. Connect the 2 rods together as one contiguous run to the main panel neutral bus bar using 4 AWG Copper wire. No splices allowed.
I also recommend that you contact the local electrical inspector as they may want the ground rod connection to also be bonded to the neutral connection inside the meter socket. Keep in mind that local electrical codes and the local electrical inspector always have the final say-so and approval.
2) Also at the main panel neutral bus bar, connect one 4 AWG copper ground wire from the street side of the city metal water supply pipe and jumper it across the water meter to the house side.
3) If the home interior water supply lines and gas piping are all metal, bond the cold and hot water supply lines and the metal gas pipe at the hot water heater riser pipes using 4 AWG copper.
See attached diagram for the water heater bonding:
4) The sub-panel feeder needs to be a 4 wire circuit comprised of 2 hots, 1 neutral and 1 equipment grounding conductor. The neutral must be isolated at the sub-panel. The sub-panel also requires a separate equipment ground bar.