hmmm...interesting idea.

2 things that came to my head. First off, be sure to use distilled water and also add something to the water to make sure that nothing grows. I would ask ppl who use water cooling if they use anything special for it. Second of all is the pumps. The pumps I remember had 2 air holes. One for bringing the air from outside and one for pushing it into the tank. In theory, you could just run a pipe from the "outside" hole to your tank. I'm not sure how great the suction is on these though and I wouldnt rely exclusively on it for cooling.