Quick Disconnects (QDCs) are nifty little connectors that let you quickly remove an item from your loop without having to drain the loop. This is very useful for example when you want to either perform maintenance or swap out a component. I love QDCs and use them everywhere. I use them for bench testing when I swap out a cpu block. I use them in builds in order to remove a motherboard tray easily. I use them on radiators in order to remove a radiator easily for dust removal.
For a long time Koolance dominated the QDC industry. They had a 3 different sizes – the small VL2, the larger VL3 and the huge VL4. Koolance refined the design and improved it by increasing the flow and relaunched the same lineup with an N suffix and this version ruled the roost for a while. Recently Koolance launched an updated QDC – now called the QD series. Other manufactuers also wanted to compete. Swiftech brought in their “Lok-Seal” design. Bitspower also somewhat stealthily launched their QDCs. Phobya also had some offerings. It seemed time to round these up and see who was king of the hill.
Koolance QD Series Quick Disconnects
Swiftech “Lok-Seal” Quick Disconnects
From top to bottom: Koolance VL4N Pair, Phobya Push Type Pair, Phobya Push Type Pair, Koolance VL3N Pair, Koolance QDC4 Pair, Phobya Twist Type Pair, Swiftech Lok-Seal Pair
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
Swiftech recently launched it’s lineup of quick disconnect fittings (QDCs) under it’s “Lok-Seal” product line. These use the standard twist method to separate but bring some interesting new features:
This is the standard QDC pair. You can not buy these individually or with different outputs however you can buy different outputs or supply your own. The pair comes in a box:
Splitting the pairs apart we see the QDC end with the central section that seals the flow and a locating pin/divot for centering the fittings:
The pair comes with one female G 1/4 thread at either end and is the only version of the QDC pair you can buy. However you can change this by buying accessories. The accessories come in little blister packs:
Swiftech sent a variety of the interchangeable accessories:
Top Row: 1/2″ ID x 3/4″ OD Compression Fitting, 3/8″ ID x 5/8″ OD Compression Fitting, Male G 1/4 Threaded Fitting
Bottom Row: 1/2″ ID x 3/4″ OD Compression Fitting, 3/8″ ID x 1/2″ OD Compression Fitting, Panel Fitting with Female G 1/4 Threaded Fitting
In order to fit these you can use two wrenchs, one on the cap to the QDC fitting, and one on the body. Thankfully Swiftech provided wrench flats on these. They tried to make it subtle though and so it’s not the normal hex pattern. A few turns on the cap and it’s off:
This is the male QDC, and the next photo is the female QDC where the cap also constrains the spring that provides the sealing:
The spring makes it a little harder to replace the cap, but it’s really not hard. Of course you don’t have to buy the accessories, you can use accessories you already own. For example if you have an unusual tubing size that isn’t supported, you could simply choose to attach your fittings to the QDC. In this shot the top is a QDC with rebranded Swiftech compression fittings added to the standard QDC base. At the bottom we see the QDC with the same size compression fittings fitted:
As can be seen, there is a space saving when using the accessories rather than providing your own fittings. This means that the Swiftech QDC system is the shortest that I have (Swiftech is the bottom pair):
Even when fitted with the male G 1/4 fitting it still gives a very small foot print ( (Swiftech is the bottom pair):
This makes it ideal for small spaces, for example when attaching directly to a radiator or a GPU. CPUs are normally constrained by the fatness of the fitting rather than the length. It’s also perfect for running in line with some tubing. However we can see that the QDC is no larger than the swiftech 1/2″ ID x 3/4″ OD diameter fitting, so if you can fit that fitting on your block then you’ll be fine. I tested the following cpu blocks to see if they could fit the Swiftech 1/2″x3/4″ compression fitting:
Performance
The Lok-Seal fittings perform similarly to Koolance’s mainstream QD3 and VL3N fittings:
Price
The Lok-Seal fittings are by far the most expensive option. I consider two main use cases. The first is in line with some tube and for this I would have 1/2×3/4 compression fittings on either end. The second is fitting to a block or a radiator. This involves a male G 1/4 on one side and a compression fitting on the other:
As can be seen the Swiftech is ~50% more expensive than the Koolance fittings. Having said that the price may not be a concern to those with high end systems who simply can not fit the longer Koolance fittings.
Summary
The Swiftech fittings bring a nice idea to the table with interchangeable heads and a compact footprint. I applaud them for trying to innovate rather than just copy the status quo. However the higher cost means that unless you are space constrained it’s hard to justify over the similarly performing Koolance QD3. The QD4 is even better in terms of flow, but is a bit of a monstrosity. The ideal QDC would have the push to release mechanism of the Koolance QD series, the flow of the QD4, the price of the QD series and the footprint and interchangeability of the Swiftech. However price is not something that should stop this product being recommended. It’s not perfect but it is a solidly performing option to consider as space is often what stops people from using QDCs.
8/10 – One point docked for price, and one point for the twist mechanism not being as nice as the Koolance one
Phobya have two types of QDCs on the market right now. There is the twist to release type as exemplified by PH-65200 and PH-65199:
As well as the push to release type as exemplified by the PH-65033:
Both types come in little plastic bags that do little to protect the fittings:
The black paint was already chipped in places on delivery. The “black nickel” finish however was not damaged:
The twist type halves are ordered seperately while the push type come in preselected pairs. The push type did not have a male G 1/4 option so I chose the female version instead:
Unlike the Koolance push to release mechanism, the phobya release must be held back as the male half is inserted. This is a bit more awkward and is further complicated by the difficulty in mating the QDC. The locater pin seems to move around and does not automatically slide into place. The temptation is to force it, but instead a bit of jimmying will usually secure a better angle and it locks into place.
The twist type on the other hand is much easier to use.
Performance
The push type was absolutely horrendous in terms of restriction.
At one 1gpm the fitting was reading nearly 20PSI. For reference at 1GPM a D5 at max only puts out about 4.5 PSI. That is astonishingly bad.
The twist type on the other hand was much better. It was more restrictive by far than any other manufacturer’s QDC that was tested but it is also much narrower in diameter. I imagine it is similar in dimensions to the Koolance QD2.
Quality
I haven’t mentioned quality on the other QDC reviews because it wasn’t necessary. However the surface on all the samples left something to be desired. The black finish on the twist type felt cheap and of poor quality. It was already dinged up and this is no surprise because it felt easy to damage. The “Black Nickel” on the other hand was also dissapointing. It felt cheaply done and had an industrial feel without the feeling of industrial longevity. It is not something you would show off in your rig, instead it feels more like something you’d tuck away where it couldn’t be seen.
Price
Phobya however does lead on price. If you want the cheapest possible QDC and don’t care about anything else, then they fulfil that niche. However if you care about quality, finish, restriction, thoughtful design and usability then it is worth paying a few bucks more for something better.
The asterisks are because the Phobya parts do not come with 1/2″x3/4″ Compressions but instead 3/8″x5/8″ compression fittings. This combined with their small size makes them much more compatible with cpu blocks.
Summary
Because of the restriction I can not recommend the push-type Phobya fitting under any circumstances. It will kill any flow in your loop. If you really can’t afford the extra few bucks to move to the Koolance QD2/3 then the twist type will work, however don’t expect to be excited by the quality.
Push Type – 0/10 – Nothing redeeming about these
Twist Type – 2/10 – Cutting corners a little too far this time
Overall I was happy with Swiftech and Koolance’s efforts. Koolance did real work to improve the usability of their QDC range. The price is right and the new mechanism feels great. They are large and I think that is the next avenue for Koolance to tackle. I’d also love to see the QD4 with a G 1/4 thread.
Swiftech on the other hand brought new ideas to the table with it’s interchangeable heads and compact footprint. The QDC works great and my only real concern is the price. Because of this and how much I like the Koolance push-to-release mechanism I have to give the edge to Koolance. However if you need or want something more compact and can afford it then I wouldn’t hesitate to choose Swiftech. Both are highly recommended.
Phobya on the other hand is a different story. I didn’t like the push mechanism or the quality or the restriction. These are budget alternatives and they are at least priced with that in mind. However they cut corners a little too far and I can not recommend them.
From top to bottom: Koolance VL4N, Phobya Push Type, Phobya Push Type, Koolance VL3N, Koolance QD3, Phobya Twist Type and Swiftech Lok-Seal
