NZXT Kraken X31 review: easy liquid cooling for Intel & AMD

Today we’re looking at the NZXT Kraken X31, the company’s entry-level all-in-one (AIO) liquid cooling system. I’ve been using a big-ass air cooler for a long time, so it’ll be interesting to see how it compares. Let’s get right into it!


The X31 comes in a pleasantly simple box, with a nice photo of the unit and a notice of the 6 year warranty – quite impressive.


On the back we have various specifications for the water block, pump, radiator, tube and fan.


Another side has the usual bullet-points-in-multiple-languages bit.


The final side has the benefits of a thicker cooler (it’s quieter) and a list of compatible CPUs: Intel Socket 1150, 1155, 1156, 1366, 2011, 2011-3 and AMD Socket AM2, AM2+, AM3, AM3+, FM1. That includes most of the big names of the past few years, including Intel’s Core i7 / i5 / i3 and AMD’s FX and Phenom series, amongst others.


One of the first things we see inside the box is this decidedly spartan instruction manual. Thankfully, directions to an online manual are also provided, and should be followed.


The other final bit that isn’t actually the cooler itself is the mounting bracket, and a selection of screws depending on the CPU that you’ll be using.



Now we move onto the proper bits and pieces, beginning with the fan. This thick fan should be much more quiet than the standard CPU fan, and its position on the edge of the case ensures better cooling at a lower rotation rate. The simple white-and-black aesthetic fits the NZXT Phantom case I’m using quite well.

The fan is a 120mm model, runs between 800 and 2000 RPM, and shouldn’t produce more than 34 dBA at max speed.


Here we have the radiator, which is also 120mm and constructed from aluminium.


The bottom pump is covered with a bit of plastic to protect the thermal paste that’s been pre-installed. It’s connected to the 400mm rubber tube, as well as power connections and the USB header that allows direct control.


Here we can see the underside of the pump, where it affixes to the processor. The thermal paste is quite perfectly applied here, I think the small smudge at the bottom was added when posing for this photo.



Now we move onto the fun part – installation. I was already using a Titan Fenrir CPU cooler, so that had to come off first. I would have liked to do this without removing my motherboard, but sadly two of the four rear screws on the motherboard were blocked by my case… so everything had to come out. This photo is just after I had finally removed my existing CPU cooler (seen on the right).


The Phantom case I’m using, sans motherboard.


I had to remove the RAM (Geil Evo) and video card (GTX 970) and unplug all the other bits and pieces. Ah well!


Before installing the new CPU cooler, it’s important to clean off any remaining thermal paste from the processor. I did this with a handkerchief and minimal force, which seemed to work well.


Now we can begin installation. First, we mount the backplate on the back of the motherboard, ensuring that the sliders are set to fit the Intel 1155 CPU I’m using here (the Intel Core i7 2600k). Then, we can screw in the standoffs – ensure you’ve got the right ones here, as the various models look quite similar!


Then, you can place the pump onto the processor and screw in the thumbscrews, securing the CPU cooler to the processor.


Now it’s time to “construct” the fan, aka screw it to the radiator. You could use a larger fan or two if you wanted, but we’ll just be using what was in the box.


Then it’s the awkward job of remounting the motherboard, while simultaneously ensuring that the fan doesn’t fall and crush everything. The fan was screwed into the back of the case, replacing the 120mm fan that was there before.


Now, connect the pump’s power supply (this is important to ensure that your CPU doesn’t immediately burn to a crisp). Once this is done, you can remove the warning notice. You can also connect the USB header so that you can control the pump from within Windows.


A better shot of the arrangement – we have a loop kind of arrangement to minimise pressure on the tubing.


There’s quite a lot of tubing available, so you’re free to choose whichever arrangement you prefer. Remember to route the other cables nicely do (as I remembered to do after this shot).


Remember I said that two of the four screw holes for the CPU cooler weren’t accessible, necessitating the removal of the motherboard for installation? Here’s why – the window doesn’t match up very well. Ah well, all sorted now.


First boot… success! New CPU detected, and a comforting glug as the Kraken X31 turns on for the first time. Everything is detected, so let’s boot up into Windows 10 and see how well this baby runs.


The whole procedure took about 2 hours, although this did include complete disassembly, reassembly and a break for dinner. I’d estimate that the actual time on installation was about 20 minutes, including all of the reassembly.


So – here are temperatures taken with the previous air cooler, the Titan Fenrir. We have two measurements – one at (near) idle, and one after 10 minutes of a Prime95 torture test.

We see temperatures of 35-45 degrees celsius at idle, moving to around 64-71 degrees celsius under load. This is a fairly well-reviewed (and giant) CPU cooler, so that seems reasonable for a stock Core i7 2600K.

Titan Fenrir (air cooled): idle + load temps


Now we have the Kraken X31, and already we can see an improvement in temperatures. The CPU is running at 33 degrees celsius at idle, then moving to 59 – 64 degrees after 10 minutes of the Prime95 torture test – about 10% cooler under load.

Kraken X31: idle + load temps

Now let’s kick it up a gear with some overclocking. We set the CPU from 3.5 GHz to 4.4 GHz and run the same Prime95 torture test. After 5 minutes, we’re up to 81 degrees celsius on one core; after 10 minutes we’re up to 86 degrees. That can’t be good for the health of the CPU – but we’re still running on the cooler’s quiet mode, just 35% fan speed.

Kraken X31: OC load temps after 5 and 10 minutes

We can open the CAM software, and see a nice lowdown on the various temperatures. If we go onto the Kraken tab (unlocked by connecting that USB header), we can change from silent mode to manual mode. Just for fun, we’ll see how the temperatures change when we go to 100% fan speed…

CAM software for the Kraken X31


At the same heavy overclock, we’re down to 63 – 72 degrees celsius, about 20% cooler and much safer, even after 10 minutes of Prime95 torture testing. Of course, the fan is audible for the first time, so it’s probably not ideal for constant use. Still, it’s an impressive showing of what this (relatively) inexpensive liquid cooling AIO is capable of.

Kraken X31: temps with OC + 100% fan after 10 minutes


It was fun to review the Kraken X31; the installation was easier than I expected and the results were convincing: lower temperatures while maintaining the same level of noise as my previous air cooler. I’d definitely recommend it even for first-time system builders, as it’s not much more complicated than installing a traditional fan and you get a lot more space to adjust other components around your CPU – that’s a nice side benefit.


  • Simple, well-documented installation process
  • Cooler, smaller and quieter than my existing air cooler
  • Supports a wide range of processors and cases


  • Fairly spartan looks
  • Higher fan speeds (and more noise) when overclocking




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