[airspirit]

Anodized aluminum is safe, as long as you don't score them somehow. It is all in your risk quotient: while I personally wouldn't risk it on principle, would you?

Further, there is no such thing as a shutoff valve that does not restrict flow. Even though they may be high flow, I would recommend two pairs of the 5/8", which would probably give you a 3/8" chokepoint on each line.

The reason to go parallel is to save your pump. Since you are using a relatively weak pump for this project (coming from someone that sniffs at pumps under 1000 GPH or 20 ft of head), you want to run the blocks in parallel loops.

The reason for any arrangement is twofold: you want to get the coldest water to all blocks possible, and you want to lower net pressure drop across the blocks to keep your flow rate as high as possible. There are two guidelines to go by here: the higher the flow rate, the higher the pressure drop in a block; and the higher the flow rate, the more effective the block will be.

Since you will have higher flow rate in series, it may appear at first glance to be a better arrangement, even though each block in series gets steadily hotter water. There is more to this, though.

When the blocks are in series, that faster flow has to pound through each block in series, and severely increases system resistance, lowering flow.

When the blocks are in parallel, each block gets colder coolant, but since the flow rate is somewhat halved, there is less pressure drop over the system to lower the flow rate further. This is the same logic we used for the heater cores.

I would hazard to guess that since you are already going to be putting alot of pressure on your pump, you will be nearly killing flow if you put them in series, and you may actually get better flow rates by putting the CPU and GPU/NB in seperate loops ... combine that with cooler water, and you'll get better performance in parallel.

When you add shutoff disconnects into the picture, you want to have the flow rate as low as possible or they will SEVERELY increase resistance. Putting them in series would not only limit the overall ID of your system to around 3/8", but would destroy your flow rates altogether. Putting two pairs (input/output) in parallel before and after two parallel loops will do much less damage to your flow rates. If you want to see that for yourself, request product information on those disconnects and be amazed at the resistance they give over a couple of GPM.

Overall, I think you will much better performance (on the order of 3-6C) if you run the blocks in parallel. Just my two cents. You could use those disconnects if you wanted to ... just be careful not to score the inner surfaces of them, and test their leakability before installation. Some release up to 2-3 cc of water upon disconnection, and you want to make sure that that isn't the case. If it is minor leakage (< .5 cc), you may be able to internally mount them in your ATX case and just wrap them in a cloth when you disconnect them to absorb the minor spillage. All disconnects will have at least SOME spillage. Also, confirm that they are dual way shutoffs. Some will only close one side leaving the other to spill everywhere (used in high pressure nozzles and such).