What's the best order for a cooling loop?
 

What is the best order for the components in a water cooling setup? In what order should the pump, block, radiator, and reservoir go in. Is it possible that it doesn't even matter? Thanks.

The most common is, starting at pump to waterblock to radiator to resevoir. This way the radiator cools the liquid when it comes from the waterblock.

Let me expand on Sean's advice. Some general rules are as follows:
Heat rises; cold falls.
The greater the temperature difference, the greater the heat exchange.
To maximize these rules, pump from low up to the heat exchanger on the chip up to a blow hole radiator back down to the pump. You may only gain a few degrees by using the laws of thermodynamics to your advantage, but a few degrees are a few degrees!

Wouldn't it be smarter to cool the liquid just before entering the waterblock? Like Waterblock-Reservoir-Pump-Radiator.

The reservoir has no reason to cool down anything, does it..? (considering a 24/24h system).
On this i tend to agree with previous posts, put the rad after the WB to maximize temperature difference, thus heat exchange.

The point of liquid cooling is to transfer the heat of the CPU (or whatever else you are trying to cool) to the water and then to transfer the heat of the water to the air.
After the CPU heats the water up it should pass through the radiator which transfers the heat to the air. A reservoir is there mostly to make filling the system easier. A chiller could be called an "active" reservoir in which its purpose would be to attempt to cool the water below the ambient temperature achieved by the radiator.
If you think about it this way then you can figure out that the best order would be: Reservoir->CPU Block->Radiator->Pump
The placement of the pump is debatable tho. I personally think it would work best if it "pulls" the water through the system into the reservoir, anybody believe otherwise?

WOuldn't you want the water to be as cool as possible before it enters the waterblock? The best way to do this, without chillers, would be to have the radiator between the pump and waterblock. Not only would the radiator disipate the CPU's heat, but also any added by the pump.

Now that I think about it that makes a lot more sense in a non-supercooling situation. I guess I never thought of the pump as a source of heat. Well I did, but I didn't think of cooling down its heat :)

belive me, i have a block > radiator > pump&res and the pump heats up a lot, i am planning on changing order to radiator > block > pump&res > pump 2

Well, I really think that all those ideas are not the best!! I've got quite a lot of space, so what I did was to have 2 radiators!! So my order is like this...

Pump--> Radiator--> Waterblock--> Radiator--> Reservoir

It seriously works, and it works good!! Also, I ducted my radiator, to increase the efficency.

Yep, Look at the DH3 and pro/mini layout its pretty clear how the order should go.

Theres only ONE rule, NOTHING should be between the radiator and the Core.. so as soon as the water is cooled off it hits the core and doesnt have time to absorb heat from any other source.