) to where you need it to be. Finally, if running a GPU block, if everything is the right length, you can simply attach the the two remaining qd's to each other to run a cpu only loop. Right now, Koolance seems to be the only company designing useful qd's. Alphacool offers a valve, but it's not only aesthetically, well, ugly, but it doesn't have the versatility of the many Koolance designs. Please post if you use or know of other valves made by other companies.
Here's what I currently have with mine:
As you can see, I have a total of four sets. One set is in the center of the case going inline from the gpu to the reservoir inline. A second set is a threaded qd going into the GPU and a barbed qd for the tubing coming from the CPU. The third and fourth set of qd's are threaded directly into the res and connected to the tubing going to and from the res through barbed qd's:
There are basically two types of qd's - threaded qd's, and barbed qd's. Of the latter, you can get either normal barbs (fixed, so you cannot remove and put on other types of fittings), or compression fittings. Of each of the above, you can get either male or female compression fittings. For each qd set, you need one male and one female. So let's cover each of the types:
Barbed - basically, the qd you're going with has either a male or female end on one side and a barb for you to put a section of tubing on the other end. If you run a barbed qd with a threaded qd, then you'll be running that set directly into the waterblock, rad, etc. If you run two barbed qd's together, then you'll run that type of inline setup between two threaded fittings (e.g. between the radiator and cpu block). Ultimately, regardless of what type of qd's you get, at least one of the pair must be a barbed qd.
NOTE: Koolance's lists these as 13mm fittings, which is the same as 1/2"ID tubing. Likewise, they have 10mm and 6mm barbs, which fit 3/8" and 1/4" tubing, respectively. Also, the clamps you see in the pictures will not work on tubing with a 3/4" OD.
Here's pics of a barbed one:
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=742
Male: http://www.koolance.com/water-cooling/product_info.php?product_id=619
Notice that you have the male and female end on one side, and the barb on the other end, where you'll need to put tubing and a clamp on it.
Threaded - The threaded ones will have one end as either a male or female qd end, and the other end will be a G1/4 thread that you'll screw into a radiator, gpu, cpu block, etc. Hence, they do not contain barbs on them as they are designed to be matched to barbed qd. These type of connectors will allow you to simply disconnect at the source of your waterblock, etc. One thing to really pay attention to is the length of two of these things together, as together (as in the male/female are together and twisted in) they are about 3". If you also consider that you'll probably need an extra inch to line up the qd before putting it in, I'd say you need to be aware of the height issue. In my Lian-Li case, I cannot place a V3 threaded one on the underside of my graphics card, as the tubing comes very close to kinking on the middle panel of the case. I'll come back to this issue later after talking about the rest of what you asked. Unlike the barbed fitting, you must fit a threaded qd to a barbed qd.
NOTE: If you ever watercool your graphics card, and choose to use threaded qd's on two of the threads on the gpu block, make sure that you buy one male threaded for one opening of the block, and one female for the other opening for the block. This will force the resulting qd's to be opposite types of qd's. The reason this is important is because you will need opposite qd's to easily swap out graphics card to run the CPU on the loop alone. I don't know if you'll simply be able to connect the remaining qd's (dunno because of length), but you certainly will not be able to run them together if you don't. It won't change the cost of what you're buying, but it helps to plan ahead.
One more NOTE: Unlike the barbed version, these don't have a "mm" width, because these qd's don't have barbed ends for tubing.
Now, pics:
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=708
Male: http://www.koolance.com/water-cooling/product_info.php?product_id=608
Compression qd's - Compression qd's are only barbed qd's, except rather than a barbed end that you can clamp down, compression qd's have compression fittings on the barbed end. Compression fittings are fittings that require you to insert the tubing up to a certain length into the fitting, then you hand tighten the compression part until it is tight. You can obtain compression fittings for regular fittings for everything in your system.
This isn't the be-all-and-end-all guide to compression fittings, but I'll list some basic advantages and disadvantages below. To tell you my bias ahead of time (it's only fair), I'm not fond of compression fittings, I have not used them (and don't plan to), and horror stories from friends (experienced system builders) have convinced me not to use them. However, they definitely have their selling points.
Advantages - You do not need clamps, as the compression fittings tighten them down. Because you hand tighten them, they are much easier to take on and off, and don't require a screwdriver. They give a much cleaner look than barbs and clamps.
Disadvantages - They are not as secure as barbs and clamps. Overtightening on the compression will cause the tubing to get brittle, and, in some cases, to tear. Compression fittings will not always work with the type of tubing you want to use. More expensive than the barbed version. More restrictive than barbed versions, as the actual bore is normally smaller.
Frankly, I think compression fittings are very nice looking, but it's something to either go all out and buy everything compression, or go with the barbs (otherwise the aesthetic look is somewhat ruined). As for qd's, you'll need to twist the qd in order to lock the qd in place, so that only adds to the possibility of the tubing coming loose. I've heard multiple people complain about fountains of water/coolant developing because the tubing was cut by the compression, or they just could not see that a problem was developing because the tubing is invisible inside the compression.
I'd rather not have this thread derail into a debate over compression fittings. If you want to leave feedback on whether you like or prefer compression fittings, fine, that's helpful. However, I think that if you like compression fittings, you probably will continue to use them anyway, which is also fine. But please don't take this too far off-topic.
Pics:
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=616
Male: http://www.koolance.com/water-cooling/product_info.php?product_id=620
Ok, now let's talk about a couple other types of qd's you can get. All of the pics and links above were to the V3 "high flow" qd's, and, for the barbed versions, the 13mm (1/2") versions. Besides just the type you can get for tubing, let me cover a couple other types of qd's.
V2 versions - The V2 versions are considered "low-profile," because they are slightly smaller, both shorter and narrower, than the V3. This is an advantage as you will be able to occupy less space, while still able to use qd's. Unfortunately, they only come in 10mm (3/8")and 6mm (1/4") sizes, and because they are smaller and narrower, they are more restrictive than its bigger brother. If you plan on going with 1/2" tubing, these are unusable. Otherwise, as a result of the extra restriction, I'd suggest using the V3's unless you really need the extra space.
Links:
Barbed
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=743
Male: http://www.koolance.com/water-cooling/product_info.php?product_id=611
Threaded
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=707
Male: http://www.koolance.com/water-cooling/product_info.php?product_id=607
Compression
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=606
Male: http://www.koolance.com/water-cooling/product_info.php?product_id=612
90 degree qd - These can be used to gain a lot of space by turning the loop 90 degrees in the direction you need. The only ones available in 90 degrees are the female compression fittings. This means you'll need to either pair it up with a male threaded, male barbed, or male compression barb qd. Significant advantages in the amount of space you'll save, but you'll be adding more restriction to the loop. Overall, it might be easier (and more flow efficient) to add a 90 degree non-QD barb or 45 degree non-qd barb and put the qd's inline.
As I mentioned earlier, I had an issue with the length of the 2 qd's together. I could have either gotten one of these 90 degree qd sets, a 90 degree threaded fitting, or run the qd's vertically on the exiting end of the block. I ended up getting a 90 degree threaded fitting and running the QD inline, as I figured it would increase flow slightly over the 90 degree qd's.
Female: http://www.koolance.com/water-cooling/product_info.php?product_id=615
Finally, there's one last cool thing you can do. If you need to mount the radiator outside the case and don't have a case that accommodates you to mount it externally, or you don't have the ability or desire to mod your case, then you can a PCI slot to have fittings on both sides of the case, to allow you to easily get your loop outside the case and back in. A few other companies have similar pci connectors, so koolance isn't your only option.
http://www.koolance.com/water-cooling/images/more/vl3-f13l_p0.jpg
Well, that's probably far more than you ever wanted to know about quick-disconnects, but let me know if you have any more questions.
Forgive my spelling, my keyboard is dyslexic
. And yes, as a note, the plating on some of the koolance parts may appear to have "freezer burn" after going down into the area of -42c coolant temps. The Q/D's will NOT fail under these condtions, I have countless hours in this territory and can say this with a high degree of confidence. If you want to preserve your bling bling looking koolance parts, avoid -7c and below. If you are an extreme junkie, well, ballz to da wallz brudda! 
