Water cooling used be seen as the domain of the ultra-enthusiast locked away in a darkened room, eking out the last drop of performance from a CPU or graphics card with home-made systems, using various bits of car radiators and parts normally found in fish aquariums. Now, however, many system builders are using it to produce silent or very high-performance PCs – and it’s not just the boutique builders either. Both Dell and HP produce water-cooled high-end gaming systems. So what’s so special about water cooling? Well as we all know, the number one enemy inside a case is heat, hence the need for so many fans whirring away. Water cooling, as the name suggests, uses water pumped across special blocks sitting on the CPU and/or the  graphics processing unit to remove heat generated by the processors, faster and more efficiently than a standard air cooler. This helps keep the running temperature of the processors within limits, and that’s why it’s ideal for overclocking. The heat generated by increasing the front-side bus speed, clock speed, and core voltages is quickly dealt with, allowing stable increases in processor clock speeds that can be way in excess of the standard speeds. As water cooling becomes more visible in the mainstream market, many people are tempted to try it out. For anybody curious about trying out water cooling the good news is that today’s DIY kits are far safer, easier to install and more complete than those of old, the source of many scare stories. You can either choose an external cooler that has the radiator and water tank sitting outside the case, pumping the water back into the case (the reason most of the cases in this review have a pair of holes drilled in the rear panel) or choose to mount everything internally using a kit from the likes of XSPC, which use small water tanks and compact radiators that replace the existing case fan(s) for tidy installations.