Many, many,,,,,,, many years ago I used to use a Unidrum for processing film. The setup worked well except eventually it starts to dribble. Most noticeably from the loading end ( there is also a moveable plug on the other end that sets the depth of the tank for the number of reels you are loading ). I later bought a jobo and the Unidrum fell by the wayside. Recently, I have been developing more B&W and found the Jobo was a bit of a hassle to set up for something that didn't really need a fixed temperature to process at ( I don't have a darkroom anymore, so I just set the Jobo up on a table when I want to use it ). I started doing B&W in a regular film tank. This works fine, but needs 400ml to do a single roll of 35mm. The Unidrum can do this with 150ml ( you might run into a minimum chemistry problem ). I tried the few fixes I found to address the dribbling but none really worked well. Cutting a new seal out of a coffee can lid worked best but still dribbled. As a last effort to revive the Unidrum, I cut a seal out of .032" rubber ( buna-n, just because I could get it in the size I wanted ). This sealed perfectly tight with no dribbles. The issue I did find with the rubber is that is is much more flexible than the original seal and can bunch up when twisting the lid on. I find a thin smear of Vasoline on the drums sealing lip takes care of that ( Vasoline was to be used with the original seal as well ). If the seal moving while putting on the lid does become a problem, I will use some removable spray mount and stick it to the inside of the lid.

Anyway, in case anyone would like to revive their unidrums, hope this helps.