[Spoilers]
You can skip this puzzle if you want. Rather than fixing the elevator, you can focus on draining the water. For that, you need to turn all the valves in that room (until you have four green lights).
[Solution]
I spent a while searching for the pentagon valve, but there isn't one (that I know of)! You can simply use the star one instead.
As for this puzzle, I think you need a "20" fuse. I never got it; I assume it's behind one of the locked doors, but I didn't find a way to open any of them. (Sorry, I know that's not much help!)