How to plumb a curved surface?

[Swingline77]

I'd like to plumb a plastic barrel. Are there any reliable ways to do this so that the entire barrel doesn't drain onto the floor? I've seen tutorials that use a standard rubber washer, but don't really know how well these work.

 

[Sierra_Bravo]

A Uniseal bulkhead is specifically made for this purpose.

 

[Swingline77]

Awesome. Thanks.

 

[AdamNC]

Uniseals alone make me nervous. I’d use a uniseal and silicone for added security.

 

[mfinn]

I used a standard bulkhead fitting on my brute topoff barrel.
It's been good for about 12 years.