Bonding with external disconnect and three sub panels

I had a question in regards to how to bond/ground three sub panels with an external disconnect for a residential house in upstate NY.

It is an above-ground 200 AMP service. The externally located disconnect is less than fifteen feet of wire from the first (200 AMP) subpanel. The 200 AMP subpanel contains two 100 AMP breakers that connect to the two 100 AMP subpanels. All three subpanels have their disconnects still installed. All three subpanels have their grounding screw removed. All subpanels have separate ground bars. All subpanels are located in the basement.

There is a ground rod that runs to the external disconnect, and then into the house. I **think** it runs to the 200 AMP panel (hard to tell after it disappears into insulation). There is a #6 solid copper wire that runs from the 200 AMP subpanel to the first 100 AMP panel, and then from the first 100 AMP panel to the second 100 AMP panel.

My questions are as follows:

1. Do I have to have a separate ground wire from the external main disconnect to the 200 AMP panel? The fat wire running from the external disconnect to the 200 AMP panel contains four wires--isn't one of them a ground?

2. Does the water pipe #6 ground wire have to go to the external disconnect, or can it go to the 200 AMP panel, or either of the two 100 AMP panels?

3. Does the natural gas pipe #6 ground wire have to go to the external disconnect, or can it go to the 200 AMP panel, or either of the two 100 AMP panels?

Thanks,
toddmanqa

 

Everything goes to the first 200A disconnect.

 

It goes to the 200 amp disconnect and it should be a #4 copper for a 200 amp service. #6 copper goes from the 200 amp disconnect to the ground rod.

Yes, you need a 4th ground wire in addition to the 2 hot conductors and 1 neutral conductor. That is why the cable has the 4th wire which is a bare ground if SER cable. You do not need a separate 5th wire.