i have taken to cleaning my 18 with ethanol in the plastic case it came in. This has solved the only complaint I had about the nail; when heating, internal buildup would smoke and fill the space in the downstem to the water line with burnt taste. (in a dry piece, you blow it out before dabbing)
also, two people I know with the 14 can't get it off their pieces. One is only stuck on an adapter but one is on a tiny recycler that needs a proper cleaning.