Closed-loop liquid cooler roundup: 8 coolers reviewed

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From supercomputers to servers to gaming PCs, water-cooling has come so far it’s changed from being a dangerous, unfamiliar technology to something you can now drop into your home PC in about half an hour.

We’ve picked a selection of the latest watery chip-chillers to help you decide which is the best one to clamp onto your gaming PC’s processor. But first, if you're not familiar with water cooling, here's what you need to know.

Want to jump straight to the tests? Jump to page two.

Terms to know

Closed-loop: The factory assembled closed-loop cooler means that it’s sealed before it comes to you and requires little maintenance to keep running. It also however mean you can’t add in secondary loops at a later date, cooling your graphics card, for example.
Active air-cooling: This simply means a CPU cooler with a spinning fan pushing air across an attached heatsinks to aid cooling. Passive air-cooling just uses a heatsink on its own without a fan, relying on chassis airflow alone.
Radiator: The water-block attached to the CPU transfers heat into the coolant which is then pumped into the radiator. Here that heat is drawn out of the liquid and dispersed through the thin fins attached to it, allowing the chilled coolant to be looped back around to the CPU’s water-block again.

Why would I take the risk of sticking liquid inside my PC?

There are inherent risks to putting a water-cooling array inside your computer, but those generally come from the open-loop, bespoke setups you have to put together, seal and fill yourself. The closed-loop coolers we’re looking at here have all been factory-sealed and, barring catastrophic design/manufacturing flaws, shouldn’t drip anything into your rig.

But is water cooling worth it? Well, water is a better thermal conductor than the air traditional fans use to shift heat away from their heatsinks. That means you don’t get such a buildup of heat around your sensitive CPU and the heart of your PC wont get quite so stressed.

So a water-cooler will keep my processor cooler than an active air-cooler?

Sometimes, but not always. The purpose of liquid-cooling your processor is not always about getting it running colder, although that can happen. An expensive, high-end air-cooler may be just as capable as a closed-loop water-cooler at maintaining a cool operational temperature for your CPU. What a liquid-chiller can do, though, is bring the CPU back down from its peak temperature far more quickly than an air cooler can.

That means you can get an overclocked chip down from a peak of 70°C back to its 36°C idle temperature in less than ten seconds rather than ten minutes. When you’re talking about overclocked CPUs especially, that can seriously extend the working life of your expensive components.

Are water-coolers only beneficial if I'm overclocking?

That’s not the only reason people like to have liquid-chillers in their machines, but it is one of the best reasons. Another is in the rise of the small form-factor PC. With today’s small form-factor hardware you can build a micro machine to perform as well as a giant rig. But when space is at a premium things get toasty and you can’t fit the chunky air-cooler you need to keep a high-end processor both cool and quiet. A closed loop liquid-cooler can squeeze more easily into a small chassis and still deliver the performance you need.

There’s also the fact that having a massive chunk of heatsink strapped to your vertically mounted motherboard can put a lot of strain onto the attachments. And if you move your machine around a lot—to friend’s or LAN parties—air-coolers can come loose and cause all kinds of destructive chaos as they bounce around inside your PC.

Are they quieter than air-coolers?

Because water-coolers still use active air-cooling to draw the heat out of the liquid once it gets to the reservoir they’re not silent. But air-coolers need their fans to spin a lot quicker than the fans attached to a water-cooler’s radiator in order to keep to the same temperature. As they’re spinning slower that also means they get to be a bit quieter too. The pump can gurgle, however.

Are there any downsides to liquid-coolers?

The obvious one is price. They’re generally a lot more expensive than a high-spec air-cooler, though prices have become far more reasonable for the smaller, 120mm closed-loop units. A less tangible problem is the fact active air-coolers don’t just cool down the CPU itself. The airflow they generate in a PC helps cool other components as a consequence. That means you need to ensure your case still has decent airflow if you opt for a liquid-chiller in order to keep your motherboard a little aerated too.

How we tested

Peak performance: I’ve used an Asus Z97 / Core i7 4770K testing rig as the base PC for this grouptest. This older CPU can get a bit toasty under peak load so is a good test for any cooler.

Overclocked performance: One of the reasons we water-cool CPUs is to allow for more stable, long-lasting overclocks, so I’ve tested each cooler with the processor clocked at 4.5GHz to stretch them.

Peak-to-idle performance: This is generally where differences in design really come to the fore. Idle temperatures are interesting, peak temperatures are important, but how quickly a CPU moves from its peak temperature back to its idle is absolutely key.

Fitting: Finally ease-of-fitting is an important characteristic. Hopefully you’ll only have to fit a cooler once, but you still want it to be as easy and hassle free as possible.

On the next page: 240mm and 360mm radiators reviewed.

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