Question about Type VII ballast tanks

[Onkel Neal]

I'm researching the ballast tank system on Type VIIs to see how we will fit it in the game.

The Type VII had many tanks, including trim tanks, torpedo compensating tanks, MBT 1,2,3,4, & 5, regulatory tanks, and a pair? of negative tanks. I say pair, because they apparently wrap around the bottom of the sub? so you have a port and stbd pair of tanks for MBT 2, 4 and the negative tank that are connected beneath the boat?

The MBT 1, 3, and 5 seem to be a set of single tanks on the centerline of the sub.

The negative tank seems smaller that I would have expected.

In the pictures of the valves 1, 2, 3; they are painted black on U-995, any idea why? Are these possibly fuel lines?

The red bar handle, any idea what this does? What kind of valve it operates? It seems like a quick-opening valve of some kind.

The pair of red/blue chain-drive valves on the bulkhead, those are for the MBT 4, and another set are located on the opposite (stern) end of the control room, they open the vents for the MBT #2. That's what I think.

Any feedback or info is appreciated.