Would depend on what you are putting through the trommel MH, mate use's his for gem stone's ,use's the water to clean the wash to find the stones but he runs the mixer dry ,he runs punched steel in it about 1/8" hole size.if you have got no water all i would use the method madtuna suggested,and yes ,longer time spent in the trommel the cleaner it is.I was down in vic about 2 years ago, i went to a bush gold and gem show, a bloke there had a home made trommel with a worm inside it (like a augar shaft) he used 2"high density poly pipe for the worm, it worked allright kept the wash in for a fair time ,he was using it for gem stones ,he said the closer the worms are together slower it takes to travel the length of the trommel and the cleaner his was was .He was running the trommel wet, but i don't see any reason why you could not run it dry