vacuum container??

So............you have a vacuum pump that only pumps air? And you are evacuating the "tank" in order to drain? What I used to use, and what USED to be easy to find are empty refrigerant cans. These things are / were handy as 'ell. I used to build stuff like air driven brake bleeders, 90 wt dispensers, and so on. I ALSO used to use them for "spare air" tanks, but got talked out of that

These have no rust protection, unless you put it there, and are pretty thin. They can rust up and become a bomb under air pressure