I watercooled my RepRap Hotend! Works pretty well. I am using the aquarium next to the printer to cool the hot-end and using the printer to heat the aquarium. Win-Win! I use a short piece of copper tubing that is carefully bent around the MakerGear hotend. A small fountain pump moves water from the 29 gallon aquarium that is next to the printer. Just straight fish-water. Everything is a bit oversized so it shouldn't give me any clogging problems. It **just** fit into the carriage. I had to run the hot end up, angle it, slip the wooden groove-mount on, and get just shy of 'rough' to slide it into place so the mounting holes lined up. It looks like over a 36 minute print, the top temp between the black insulator bit and the copper cooling tube was about 110f. No thermal grease was used, so I may be able to improve the heat transfer some yet. Some of the other mods on this video is a hard-wired USB cable (not shown, but the main reason the printer hit the work bench) because the jack had gotten sloppy and connection was getting flaky I also drilled holes in my binder clips to make them less likely to break my mirrored glass print bed with a death-grip. I added a bit of clear PLA to my mortised in heated bed PCB to act like a fiber-optic bit to make the power LEDs move visible. I also incorporated the overclocker's temperature monitor into the printer better - it's no longer a bunch of loose wires. The other water cooled RepRap I've found is http://blog.reprap.org/2012/07/water-cooled-hot-end.html ... https://www.youtube.com/watch?v=-NlOCluFxck