Peanut butter and jelly. Han Solo and Chewie. Expensive electronics and liquid. One of these things is not like the others. Anyone who has suffered a keyboard spill or fished a smartphone from a toilet bowl knows that liquids and electronics often aren’t compatible.
But, when it comes to PC cooling, sealed all-in-one (AIO) liquid cooling systems—also known as closed-loop coolers—are safe, effective, and easy to install. Indeed, in such instances, water is a PC’s friend!
While the stock air cooler that ships with most CPUs is perfectly adequate for everyday computing, that heatsink-and-fan combo will struggle to cool gaming systems and other high-performance PCs. At the other end of the spectrum, hardline cooling—which uses rigid tubes and a liquid reservoir—can look spectacular but requires careful planning, user-assembly, and a significant investment in leak testing. It’s the perfect project for plumbers, but for those taking their first steps in advanced PC cooling techniques, an AIO is the way to go.
Here’s everything you need to know about closed-loop AIO coolers, from how they function, to how to pick one for your needs, to the steps for installation.
How closed-loop liquid coolers work
AIO coolers work in a similar way to a car radiator. A pump, positioned on top of your CPU, circulates a special liquid (usually a combination of distilled water and a thermally conductive fluid) around a soft tubing system, configured in a closed loop. Heat is transferred from your CPU to the liquid via a copper plate on the base of the pump.
The warm liquid travels through the tubing to a radiator, which can be mounted near the top, front, or rear of your PC case. Heat is then dissipated from the radiator with the help of fans, which can be mounted in various configurations for optimal cooling. The cooled liquid then travels back to your CPU, where the process begins again.
As AIO coolers are available with various radiator sizes, they can be put to work in a wide range of PC form factors. That said, they’re best suited to medium and large desktops. Most coolers are fitted to processors, but some can also be used for graphics cards, too.
Choosing a closed-loop liquid cooler
Today, we’ll be installing an NZXT Kraken X62 AIO Cooler ($160 on Amazon) in a typical gaming PC rig. It’ll be employed to cool a 4GHz Intel Core i7-6700K CPU ($330 on Amazon) which, with a 91-watt TDP, can get a little toasty under load.
Before settling on an AIO model, I always recommend that you spend some time reading reviews of the leading contenders, including user reviews on Reddit’s Build a PC subreddit and sites like PCPartPicker.
You’ll obviously need to find a closed-loop liquid cooler that fits inside your PC case. AIOs are available in single and dual-fan configurations, with the latter supporting longer radiators. As mentioned, you can install the radiator in various positions in your case, but you’ll need sufficient clearance for the radiator itself and the cooler’s tubing (which has some degree of movement for routing), and to ensure the integrated fans can spin freely. Some cases will allow you to remove unused drive bays or entire drive cages, which can ease installation.
Take some time to investigate the space available in your case and research how other users have installed single or dual-fan radiators in your model.
As AIO cooling systems include moving parts, such as the pump and radiator fans, not only should you consider cooling performance (CPU and system temperatures) in your research, but you should also look for low noise output, long-term pump and fan durability, and—of course—zero leaks. Specification sheets and expert reviews are useful for building a short list, but it’s important to understand how a cooler maintains performance over time. Think year one, two, and three, alongside day 1,one, two, and three.
Be sure to check the manufacturer’s warranty policy and support options. Some coolers benefit from long-term warranties (up to five or even six years) but find out whether this applies to third-party components that could suffer leak damage. If you need to return the cooler (and other parts), does the manufacturer cover two-way shipping? How quick and easy is the returns experience? All of these factors combined should help you identify the best AIO liquid cooler for your needs and your budget.
As with most PC parts, you’ll find that AIO components originate from a small number of specialist OEM manufacturers that supply the major brands—Asetek being one example. Check out the full range of models from Cooler Master, Corsair, SilverStone, EVGA, and NZXT to find the right combination of size, features, and performance.
PCWorld’s graphics card testing system has been cooled by a Corsair H100 ($102 on Amazon) for several years, with no complaints whatsoever.
Next page: How to install a closed-loop liquid cooler