I can't do without my Franford Arsenal Rotary Tumbler (F.A.R.T.) But sometimes the lid leaks despite my tightening the caps with Herculean strength using a F.A.R.T. wrench! So I tried something new. All I did was stop the leaking unit & turn the drum over. Swapped ends so to speak. Leak instantly stopped! Apparently the lid rotating in the direction that it's screwed on can cause the leak - I'm guessing. Try it yourself if you ever have one end dripping. Worth a shot....
Just FYI