Building a Water Chiller is just like building a Phase Change system, if your building from scratch that is.
The only difference is the evaporator or lack of in a water chiller.
With Water Chiller's there are many different designs for the HX (Heat Exchanger), some are simple and some are complex.
The best thing about water chilling is that it can be easily done by taking a working Air Conditioning unit and placing the evaporator (look's like a large radiator) and placing it into the reservoir, where the liquid coolant is held.
Don't confuse the evap. in the Air Con system with the Condenser though, just put your hand up to them, the cold one is the evap.
When using a water chiller you must condensation proof your motherboard and surrounding areas just as you would when using Phase Change, you'll also have to insulate the tubing and water block.
Because the coolant is now below freezing you'll also have to put anti-freeze into the reservoir to allow the coolant to go below freezing.
Remember that you'll also have to use an approved pump, any good quality metal pump will do, plastic one's will just crack. It's the same case for the water block, you must use one with a metal top and your tubing must be capable of going below freezing aswell, Tygon R3603 is capable of going as low as -73c while staying flexible and not cracking.
If you have any question's feel free to PM me