"the key" ... day tank

I watched (bought) that movie “The Key” someone talked about here a while back and believe I was visiting a similar vessel tied along side us at Hickam. It was being towed out for fish food but I remember the day tank being amid ship in a ladder well and i swear the thing couldn’t of been over 25 USG.
Crimany, you’d have to fill it every 20 minits? an older cme that ran that class told me is was the day tank. Now I’m thinking it was a inline settling tank, this should probably be in engineering catagory but does anyone have a comment on this? 20 yrs. later it still bugs me.

Could she by any chance have had a Diesel Stove in the Galley? I’ve seen older vessels with these stoves that had a tank of about the same size that fed the Galley Stove.

It may be a FO header tank. I worked with MWM engines late '70s, early '80s that were set up with that. The engine driven fuel pump flowed through the strainers and filters into the header tank and overflowed back into the day tanks. The fuel rail pressure was constant from the height of column.