On Feb 15, 1:16 pm, (UglyDan(R)(c)(tm)) wrote:
The barrels will have to be horizontal of course, but make sure the
bungs are vertical or perpendicular to the waters surface, and again
make sure that the bungs have gaskets. It's also important that the
lower bungs are free from any obstructions, this makes them easier to
service with a air compresser should you develop any future leaks, That
way it makes my job simpler when you have to hire me, or one of my
counterpart's to come fix it.

And that's why filling with expanding closed cell foam is a good idea.