After designing 10-15 water cooled systems consisting of everything from 2 cpus up to 16 I thought I would pass along some words of wisdom.
First and foremost SCREW WORM CLAMPS. They always tend to leak in a computer application. Zipties or the plastic click clamps for whatever reason work better if you must. Of course all your blocks should be compression fittings, but there are times, at the pump, you have to settle for a clamp.
Second, use motul coolant. Its ~ 1/10 the cost of computer specific coolant and its the exact same thing with the exception of possibly a UV dye.
When water cooling you still need at least one fan. The case will heat up if you do not install at least an exhaust fan.
WATERCOOL THE GPU. Im sick of seeing people say the new ATI/nVidia have uber leet fans that cool them fine. I half assed my last case and the GTX 260 cards ran at 180F. After a CPU leaked on the top card, and shorted it....stupid freaken worm drive, I replaced it with a water cooled card. Same card, well not the same one since I Fed it up but same model, now runs at 115F. If 65 freaken degrees is not worth the trouble to you, stick you computer back in the box. Don't get me wrong. I know why people say this. They are too cheap to drop 300 bones for GT form factor waterblocks. Lets see. What else? Oh!
Run dual loops if you have more than 6 blocks. You can get by with a single reservoir and radiator if you use a large enough one, but you want 2 pumps.
TYGON IS YOUR FRIEND. PVC turns brittle over time. Never seen it leak, but it will be come so stiff it becomes hard to work with an remove should you need to.
Fill ports on the top of the case will save you a lot of headache. Sometimes you just don't want to open the case and see that link when its time to top off.
Kidding. Your system should not leak but its not uncommon to have to top off from time to time.
Should be obvious but make sure you have a strong power supply. Most pumps are running around 2 amps.
No matter how much you plan, until you have a parts bin water cooling = waiting for parts to arrive. First several systems I built I always forgot to order parts. Thankfully now I have a decent collection of 5/8s to 1/2 adapters, clamps, water blocks and so on. Despite the inevitable take your time and plan your system. After going the water cooling route I cannot see myself running an air cooled system again. Especially in my shop where air cooled = metal shavings all in my case shorting out more parts that water :lol: