The end outside of the container can have any number of means to attach a hose or pipe; like a barb, flange, thread, etc. For your application you will want a barbed bulkhead so you can just put a hose on there and don’t need to worry about the additional cost and work involved with rigid pipe.

Ah, I've seen those kinds before, and that seems fairly simple. Thanks!

As for the stain issue. The type of container you described leads me to believe it is a typical plastic storage box, almost all of those have a taper to the sides.

Of course, now I understand what you meant! Yes, the boxes are slightly tapered, so that would be an issue.

Tube and barbs also have the benefit of being easier to connect across a short distance and ensure a watertight connection. I would recommend putting the tube on both sides first, then installing the bulkheads in the containers to make life easier and avoid damage when trying to press the tube on the barbs after the bulkheads are installed.

Great tips, noted! Now I'll have to figure out where I can buy these locally.

Thanks again for great help!