Found this bit of info on the flasks.
The impulse flasks, forming part of the impulse air system, are steel cylinders, dome-shaped at each end. One of the domed ends is flanged and is provided with a port which connects to the impulse lines. There is an impulse flask for each torpedo tube. The six flasks that are mounted in the superstructure above the forward torpedo room are approximately 5 feet 10 inches in length and 16 inches in diameter; the four flasks mounted below the after torpedo room deck are approximately 5 feet 3 inches, in length and 18 inches in diameter.
Eric...