QUOTE(fiber optic @ Jul 5 2004, 09:03 PM)
I've seen sewer pipe with a smaller diameter than that tubing.

What kind of flow rate does your pump do?
Those large diameter hoses and fittings aren't just for high flow rates.
Larger diameter hoses will have the exit pressure as a small diameter hose but since there is more surface area, the surface pressure per inch is a lot less. This makes the hose less susceptiable to breaking and fitttings from coming off because the system is under a lot less stress.
That cooling could be made with hoses 1/4 that size but would be more likely to break and, inside a computer, that would be very very bad.
If my understanding of simple hydraulic principles is wrong, please correct me.