I agree with Tony. I'd like to add that even with "room temp" water (IE no ice) an air/water setup has shown to be more efficient than an air/air. I forgot the exact number, but I believe water can take over 200 times the amount of heat out that air can. So you can see it doesn't take much to work (thats why most air/water cores are nowhere near as big as an air/air, they are just far more efficient). Hell I can fit Dave's (Rales) air/water core in my pocket (I've tried to steal it before ) and it works great even at 35psi