Koolance QD Series

Koolance’s latest Quick Disconnect series is called the QD series. It retains much of the same trusted internal design but uses a snazzy new push to release mechanism rather than the older style twist mechanism.

The QDCs come in three different sizes – the QD2 (not reviewed) is the smallest and is pretty high restriction. Only use this if you have space issues. The QD3 (left in the above picture) is the “mainstream” QDC, it is designed with most liquid cooled PC’s in mind. The QD4 (right in the above picture) is the big brother of the QD3. It’s really designed for more industrial applications where a high flow is more concern than space. Although it’s not that much bigger it makes it difficult to use in a PC. It also comes in less varieties than the QD3. There are no right angle versions or G 1/4 fitting options. It does however come with a G 3/8 size and Koolance sell a convenient G 1/4 to G 3/8 adapter. Koolance have at long last also figured out how to make these in black. Previously Koolance didn’t do this because the tolerances were too tight to use a standard black finish, however they found a finish that was compatible.

The QD4 comes in it’s own box and is well protected. This is good because the old VL4N series could be damaged when dropped a few feet. The QDCs do not get sold as a matched pair, instead you buy a female or male half of the pair individually. These are the male and female ends of the QD4:

The other end can either come in a G 3/8 male thread or in a compression fitting:

The threaded versions has wrench flats for easy tightening down. The QDC3 on the other hand comes in a standard fitting baggy:

No special treatment for you mainstreamers. The QDC ends are protected with a rubber cap:

The QDC3 is the more practical size as it can easily fit on common blocks including Koolance’s own CPU-380:

A pair of QDC4s on the other hand does not as they are just too fat:

The new push to release mechanism has contributed to that fatness:

Comparing the old with the new we see that thought the length is similar the fatness is new growth:

The mechanism is however nice. No twisting means you’re unlikely to unscrew a fitting attached to the other end of your tube. The release is also quick meaning less drops to spill and the spring tension is perfect. Whether it holds up to time is the big question that VLXN series owners will want to know. As the internals have not really changed we suspect that spring wear over time may continue to be an issue. Performance The similar internals are seen again in a plot of the QDC’s restriction (resistance to flow):

The QD4 is still top dog in terms of high flow and the QD3 still performs decently too. My major complaint is that the QD3 is still fairly long and that makes it look ungainly and somewhat awkward. The QD4 on other hand is very fat now which makes it less compatible with CPU blocks that have narrow port spacings:

Price

The Koolance provides a strong price argument. It’s more expensive and higher in quality and performance than the Phobya, but much cheaper and similar in performance to the Swiftech.

Summary Overall the new QDCs from Koolance are an improvement to a strong competitor. Although restriction has not changed, the new push to release mechanism is welcome. It’s not just for looks though, it speeds up the disconnecting process, removes the worry of loosening a fitting and is more resistant to clumsiness. If you have space for the limited and pricey QD4 choices, then they would be my first choice as annoying as G 3/8 is. If not The QD3 trades blows with the Swiftech Lok-Seal. The choice comes down to price, shape and aesthetics as they are both good fittings.

Overall 9/10