Don’t do this to your AIO

Using an AIO is the easiest way to get into water cooling, but there is a right way … and a very wrong way.

Unlike a high-end custom water loop, with its pumps, reservoirs, radiators, tubes, and connectors, an AIO (All In One) water cooler is a sealed unit that is not much more difficult to install than a high-end air cooler. These are an excellent way to water cool a system without resorting to the complexity of custom loops. My two primary machines are both using AIOs (Cooler Master MasterLiquid ML120L). Read the full description here.

Installation would seem to be as easy as mounting the pump/heat-sink assembly on the motherboard, and attaching the radiator/fan to the case. The only complication would appear to be the placement of the tubes to avoid kinks and other components.

Or so I thought until I saw the video by Steve (Gamers Nexus) pointing out that there is in fact a very wrong way to install an AIO. There were several follow up videos from other YouTubers about this issue.

The problem is that being a sealed unit, any air in the AIO is trapped and will make its way to the highest point on the loop (and there will always be some air inside). If this high point is the pump, then there will be problems as water pumps do not work properly when full of air, and it will quickly fail.

Now this would seem obvious, but I had not considered this before. Usually this issue would not occur, as with typical layouts the radiator would be mounted on the front, back, or top panel, so the highest point of the radiator would always be higher than the pump.

However, a number of manufacturers in recent years have released ultra-small form factor cases (and builds based on these). Being such small cases, with extreme component density (such as the NZXT H1), there often isn’t any choice of layout – the case is designed in such a way that everything has it’s place and only that place. Because of the small case size and lack of air flow, an AIO is an obvious choice. Unfortunately, a number of these designs place the AIO radiator in the bottom of the case, which means the pump is most definitely the high point. These designs will have problems.

I’m not sure what the solution would be. Either use an air cooler or get a different case. The AIO manufacturers will have to consider this issue when designing future pumps, though I’m not sure what they could do to eliminate the problem.


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