your coolant is likely to get to 40C or around there, so you will probably have a lot evaporating. This water tower has me so psyched for my summer rig in the summer, i have already thought of so many things to do with it, some not so good. I am also intrigued by this concept of the huge pvc housing, what if you made a huge copper coil and had a few fan blowing up, that would be a great radiator! lets see, how could we improve on an already great thing, the mister sounds great, you just might end up loosing a lot more water that way. My concern is vapor loss and how to reduce it. What if a condenser loop of some sort was added., especially if a mister is used. That would reduce the amount of vapor escaping. I really like the idea of the waterfall design, could run some on the outside and make some nice little sculpture thing. My main concern is the mist, but by adding maybe a u type thing would keep mist from coming out. This is definately worth pursuing, i love this idea! This is gonna be used in my water cooled system this summer.