Remember the heady days of the Pentium 4, when a single CPU could generate enough heat to keep you warm through winter?

They were great for cutting down on household utility bills, but as soon as the weather started to improve, systems would fall over as the mercury rose.

They were also slow, and their performance aged quickly. As a result, many of us looked to watercooling to bring down core temperatures. This in turn reduced noise and increased the useful lifespan of our components by just a few months through overclocking.

To meet demand, early online component stores were stocked full of arcane heatsinks, boasting hand-milled plates and liquid cooling that looked like something ripped off the back of a refrigerator. The weirder, the better.

A quick flick through the catalogue of any online retailer now, though, suggests that the golden age of cooling is over. It’s almost impossible to find a TEC-based chiller, and there’s clearly no demand for funky accoutrements, such as UV lighting and external tanks.

It’s not surprising. The most recent, fastest quad-core processors won’t even make an Eskimo sweat. This is due to the move to ever-more ludicrous efficiency and 32nm manufacturing techniques. Air coolers are far more effective and quieter than they ever used to be, and overclocking is hardly a necessity when a three-year-old CPU can cope with the latest games.

Or so received wisdom goes.

The joy of watercooling has never been about its practical value. It’s about taking a system and personalising it in ways that lesser mortals can’t even imagine.

It’s about mixing electronics and liquids with panache and bravado and creating something that isn’t a slowly sparking mess. It’s also – as it always has been – about beating The Man. Sure, you can buy a shiny new four or six core processor for £150 and get top performance with just a bit of heat paste, but where’s the satisfaction in that? How much more impressive is it to hit the same benchmark score for half the price?

It’s possible, and we’re going to show you how to do it.

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One of the historical drawbacks of watercooling is that it’s tended to be quite expensive. Saving £70 on a CPU by spending £300 on a radiator and pump might earn you a certain caché in some circles, but it won’t earn you the Nobel Prize for Economics.

To make matters worse, while watercooling was essential for overclocking, many people dabbled in it to silence noisy PCs for media centre work. Unfortunately, many self-built systems tended to be as loud, if not louder, than a decent fan.

Cool trends

If you’ve been watching closely, though, you might have noticed one of the more intriguing trends in component sales that’s been going on recently. There’s been a dramatic drop in the cost of self-contained CPU cooling kits. These units are relatively new, and are designed to make watercooling simple, cheap and risk-free.

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If you’ve not seen one before, these boxey devices combine everything you need for watercooling in a single unit. The bulky part will contain a pump, reservoir, radiator and a fan which bolts onto the rear exhaust ports of your case. The other end is attached to a CPU block. Everything is filled with fluid and sealed in the factory, so you don’t need to risk getting your PC wet or worry about checking the levels and refilling at a later date.

Pioneered by Canadian outfit CoolIT Systems, the first self-contained coolers appeared four years ago based on designs used in server farms. These original models came with a clever control panel, but overall it had two significant flaws: it was expensive and arguably less effective than a run of the mill £20 air cooler at keeping temperatures down.

That was then, however. Now, several new revisions have vastly improved on the original design, which has been further pushed on by competition from the likes of Asetek. Modern all-in-ones are everything they promised they’d be.

Starting at around the same price as a high-end heatsink of the traditional variety, the self-contained watercoolers of today are whisper quiet and can chill a chip at one thousand paces. Cooler Master has even gone one further, building a self-contained Peltier-powered CPU cooler, the V10 .

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CoolIT, meanwhile, has just gone into partnership with Corsair to increase the market for its all-in-ones, and the first product of the union is the H60.

Staying breezy

While the watercooling purist may look upon these all-in-ones with scorn, they do work and, cost-wise, are a bargain. There’s only a £10 difference between a midrange air cooler and the H60, for example, and you’ll not only get better performance from the latter it looks a lot better too.

As far as designing a complete system goes, though, the only thing you need to consider is that the unit which replaces a rear case fan does contain the radiator from the CPU, which is cooled by drawing air across it towards the vent.

So if you have a lot of other hot components, you’ll need to make sure they aren’t heating up the inside of your case to the point of rendering the CPU cooler useless. In other words, remember that just because you have one of these, don’t think you can skimp on fans elsewhere.

When it all goes Pete Tong

So you’ve sprung a leak, and your PC has begun gently sparking away to itself. That’s not good is it?

First things first, don’t panic. Although water and electricity aren’t known as the best of bedfellows, the damage is probably not as bad as you think.

The first thing you should do is pull the plug. Hit the main trip switch on your fuse box. Even turning a PSU off using the power switch around the back may not stop it drawing current, so removing the cable is the only safe option. Pull the ATX connector from the motherboard too, just to be sure.

Your next job is to dry everything thoroughly. Mop up any obvious spillages with an old cloth, and then leave your machine in a warm place. Ideally, you should take components such as the motherboard out and dry them separately, but 24 hours next to a radiator should do the job. With a bit of luck, that should be all you need to do, and your PC will work when you boot up, but do remember two things.

First, the obvious: fix the leak and make sure the cooling system is working properly before you plug everything back in. Second, remember that the power supply is where the big voltages are, and that underneath the cover there are a lot of capacitors, which store up electricity for various reasons.

If the PSU is wet, then, take extra care. In the old days, when PSUs were sited at the top of the case, this wasn’t so much of a . New cases, though, tend to put the power supply at the bottom, exactly where water will gather.

How easy is water cooling?

Fitting a self-contained watercooler is only marginally more complicated than attaching a standard heatsink. The main complication is that the CPU block is always attached to the radiator and fan assembly, so manoeuvring the two into position can be quite a tricky process.

A PC case with access to the back of the motherboard is essential, but even then it’s easy to pull a bit too hard and unhook a pipe – which means writing the whole kit off.

Building your own system isn’t hard, per se, but you do need a lot of patience to assemble carefully, tie up pipes safely and check all the seals as you go. The biggest danger to any watercooling set-up is rushing it and botching the job.

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A minor point before we begin, but the term watercooling is a slight misnomer. The fluid that’s pumped around a liquid chilled PC is rarely just a couple of Hs with a bit of O. Usually it’s mixed with some sort of additive in order to improve efficiency and prevent limescale build up or corrosion of the plastic parts inside your system.

You could use distilled water – if you were sure that there’s absolutely no mineral content that might get left behind in the radiator – but it’s really not worth the long term risk. Especially when coolants come in a range of funky colours.

That minor quibble aside, all water systems are based around a similar set of components – a pump, reservoir, heat transfer block, piping, a radiator and fan. They vary in size from giant external towers like the Zalman Reserator V2 series to compact all-in-ones like the CoolIT Eco ALC , but the principle is always the same.

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The coolant (let’s just call it water for simplicity) is poured into a reservoir or tank, which in turn is connected to a pump unit. The reservoir level will need checking and topping up every once in a while, as water will evaporate thanks to the heat, and it’s a good idea to drain the whole thing and clean it every six months or so too.

The pump pushes the fluid out through a network of pipes to a block of highly conductive metal, usually made from copper or aluminium. This block has one finely milled side, which is clamped on top of the CPU – or GPU or Northbridge controller chip on older motherboards – and has narrow channels running through its core. The water flows through these channels, absorbing heat from the rest of the material, and then exits the CPU block on its way to a radiator.

At the radiator, the water is pushed through a network of even narrower channels, which are cooled by having air blown over them by a fan. It is possible to build a passive watercooling system, like the Reserator V2 mentioned above, but they tend to be larger in order to give the water enough time to cool down to match room temperature, and are less efficient. The water then flows back to the reservoir and begins its journey again.

Efficiency is king

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The obvious flaw with watercooling is that even with a fan assisted radiator, you can’t cool the fluid below air temperature. It’s possible to find a radiator that’s connected to a more sophisticated heat exchanger, like a TEC unit or a compressor of the type more commonly seen in refrigerators. These are relatively expensive, though, and increasingly hard to get hold of as they fall out of fashion.

Just because a normal watercooling system can’t drop the core temperatures below zero though, doesn’t mean that you might as well stick with an air cooler – the important point is that they’re very efficient, keeping chips colder for longer while they’re working under load, and getting them back down to room temperature faster once they start to idle.

For most systems, there are two ways of improving the cooling capacity: you can either increase the fan speed by the radiator or turn up the water pressure on the pump control. Either option will increase the noise levels, and it’s important to read reviews and get recommendations before you invest in a potentially pricey system.

I’ve tested pump units that are not only noisier than any standard system fan, they have a similar effect on the bladder to standing beside a large fountain too. You don’t really want that if you find yourself stuck for eight hours with a particularly intransigent raid leader, do you?

Designed for life

With those parameters, of course, there are lots of permutations when it comes to the kit you can buy, although the choice is a lot more limited than it used to be in the past. Even, which pioneered sales of watercooling components no more than a few years ago, has a relatively small selection of Zalman kit on its site now.

Only really niche specialists, such as, carry much in the way of choice of components if you want to build a system yourself these days.

It’s not essential to get parts for an entire system from the same manufacturer, but several websites carry a lot of XSPC gear either as separates or complete kits, which makes it one of the best brands to watch out for.

In terms of design, the most popular variants that have been settled on are self-contained CPU coolers or reservoirs that sit inside two or three drive bays at the front of the PC, which have a built in pump and controls that become part of the front panel.

Apart from adding a certain je n’ai sais quoi to your machine, it means the whole thing is contained within the case. Otherwise, you’ll need to pipe water out of the back of the case to cool it.

Pumping action

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Drive bay pumps tend to be noisier than external units, because they use smaller motors and vibrations will be magnified by the case itself, but they do have the advantage of taking up less room and leaving your PC relatively portable still, if somewhat heavier than before. There’s also less chance of tripping over external units and spraying coolant on the cat (there’s a joke right there – Ed).

Connecting the various parts of a watercooling system up is generally straightforward. Most are designed for the hoses to sit over rubber seals and be locked into place with jubilee clips.

What’s important to remember when designing your system is that if you’re planning on using a watercooler for overclocking your CPU, you may need to consider heat at other points on the motherboard too.

Processors from AMD’s Black Edition series or Intel’s Extreme Editions have unlocked multipliers which means they can be tweaked independently of other components, but for anything else you’re going to be raising bus speeds across the board. That means you might want to add in watercooled heatsinks for your RAM and graphics card, which is considerably trickier than just chilling a processor.

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For a start, you’ll need to get the flow of water around the inside of your case right, running it over cooler components first and possibly adding a second radiator to drop the temperatures between – say – the GPU and CPU. It’s a bad idea to take fluid that’s already warmed up and run it over a cooler component if you’re trying to reduce its temperature.

At the very least, you’ll need a double width radiator to disperse the heat. These usually bolt over two fan slots at the top of the case and are slightly noisier than a single unit.

In principle, that’s all there is to watercooling. Every system is unique, and it’s a good idea to clip back errant hoses with cable tidies to stop them snagging if you need to pull out a part, but it’s really not as complex as you might think, and modern systems are usually well-designed when it comes to preventing leaks.

Worth the pain?

Is it actually worth it, though? After all, a full kit can cost over £200, and you’ll need a decent motherboard to push the CPU to any great extent too.

Some people seem to think so. All Cyberpower PCs, for example, are sold with watercoolers as standard. We asked production manager David Scott why that is: “Any water cooling cooler we have used will allow you to overclock a PC,” he said.

“And the price of self-contained units are practically the same price as a decent air cooler anyway. The risk of water damage on a self-contained unit is very low, and because of this most manufacturers will guarantee the warranty on the parts affected by a leak. Custom built kits look amazing and you can get top end performance that only cryogenics (LN2 or Phase-Change) will beat.”

How good is it? Well, it can certainly help to close the gap between AMD and Intel, for example. Using a watercooled rig to overclock a six core Phenom II 1100T (£200) to 4GHz, we brought it within 16 per cent of a top-end Core i7 2600K (£260) in gaming and video encode tests.

More impressive, however, was taking a £50 Athlon II 255 chip and giving it the water treatment and a few BIOS tweaks, had it running at 3.9GHz and easily matching any dual core Phenom II in the benchmarks.

That’s performance enough to justify the cost of a self-contained unit, and potentially a great way to revive an ageing PC.

Ultimately, though, watercooling isn’t about cost. It’s about the joy of building and tweaking a PC and knowing that, in these days of superfast stock CPUs and tablets, there’s still space to create something unique.

Something slicker?

If the main reason you’re interested in watercooling is to reduce the sound of noisy fans, why not make your PC completely silent by submerging it in oil?

Stripping your system components of all moving parts and then sinking them to the bottom of a tank of mineral oil is a well-known way to achieve the most consistently low temperatures possible. The oil itself is non-conductive and doesn’t harm components, and so long as the tank is large enough that heat is shifted away to the surface by natural convection currents, you won’t need any pumps.

That does mean that oil is no use for extreme overclocking, because you can’t chill components below ambient room temperature. But for a media centre, say, it’s near perfect – except for the fact that any peripherals that plug directly into the motherboard are likely to make a bit of a mess on your living room carpet.

Oil cooling has been around for ages. The early Cray 2 supercomputers, for example, were kept at stable temperatures using this technique and US start-up Green Revolution Computing is pushing the technology for data centres, where it can be considerably cheaper than CPU fans coolers and banks of air conditioning.

While mineral oil is preferred for this type of heat management because of its non-corrosive nature, it can be hard to get hold of in the UK in large enough quantities to be practical.

Emptying individual bottles of baby oil into a 30 litre tank, for example, would soon get quite expensive. Other oils can be used, but the drawback is usually that they smell. Vegetable oil, for example, makes a fine coolant – so long as you don’t mind your PC smelling like chips.

Something a little colder?

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The big daddy of component cooling remains, of course, liquid nitrogen, or LN2 to its friends.

Contrary to popular belief, liquid nitrogen is not the coldest fluid known to man, that honour goes to helium which has a boiling point 100 degrees lower than that of LN2, but nitrogen is the PC enthusiast’s coolant of choice because it turns into a gas at -196 °C and is relatively cheap and easy to purchase – providing you have a cryogenically safe Dewar flask and convince your local industrial chemical supplier that you’re capable of handling it safely, that is.

Using LN2 to sub-zero temperatures, hardcore overclockers are able to hit clockspeeds of over 8GHz on a Cedar Mill Intel Celeron chip. The cooling effect is achieved by attaching a flat bottomed tube, or ‘pot’, in the heatsink position which can be filled with LN2 just before the CPU is switched on. It’s not much use for day-to-day cooling, as even a full pot will evaporate in minutes.

While it sounds simple, there’s a lot more to it than that. For a start, the engineering of the pot has to be immaculate. Any minute ridges on the surface of the CPU or base of the pot could cause the chip to crack when the LN2 is poured in. Then there’s the problem of condensation: as water forms on the surface of the components, it can create short circuits and damage the system.

In fact, it often takes months of preparation to get a board and CPU working stably with LN2. Practice runs with mechanical phase change machines at slightly higher temperatures will be needed to test the thresholds of the equipment, and motherboards have to be customised with soldered in resisters to get the kinds of voltages that BIOSes just don’t allow, but are needed to go several gigahertz above the operating limits.

As far as we know, there are no recorded episodes of overclockers injuring themselves by using LN2, and when handled correctly the liquid itself can be quite safe.

Arguably, the best way to indulge in LN2 overclocking would be completely naked, since the liquid itself boils off of skin before it can do any harm – thankfully though, there are no public records of naked overclockers, although a YouTube video is bound to turn up now.

That said, it’s not something we’d advise you to try without a lot of experience in both handling dangerous chemicals and overclocking PCs. Even the experts are shaken by LN2′s reputation and terrifying characteristics, and many of the best stick to slightly less challenging techniques like using dry ice for equally impressive results.

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In Depth: PC water cooling guide: all you need to know