Premium Build: Greyscale — building a custom-looped ITX PC that pushes the form factor to its limits

Loop Planning

During the planning phase, I had a pretty good idea of how to run the loop; however, things never go according to plan, especially with smaller builds like this. I had ordered a couple of extra fittings and extenders, just in case. I had four short extensions, four longer extensions, four 90-degree elbows with rotary ends on both sides, and four 45-degree elbows, also with rotary ends.

Rotary ends are particularly helpful, as although they cost a little more, they let you rotate a fitting without breaking the seal, which makes it much easier to get pieces to fit. A luxury in big builds, a necessity in small builds.

I had also ordered a drain valve, and a thermal sensor. I like running my fan curve based on the coolant temperature, because when all is said and done, the fans cool the coolant, not the CPU or GPU. Especially if both are contributing heat to the same loop, it can cause weird behavior to run the loop based on their temperatures.

However, the MSI MPG X870I Ti Edge Evo doesn’t have a connector to hook up a thermal probe, which put a damper in those plans.

It’s nice that I could lift up pieces of the case to get easy access. At first, I thought of running the reservoir’s outlet straight to the GPU’s inlet, but found that this would cause collisions with other routes.

After much puzzling, I decided to run the reservoir outlet (bottom port) straight to the CPU block’s inlet.

I installed the tubing, cutting off a few mm at a time until I was happy with the fitment.

I decided to get this pesky corner over with. In the plan, I wanted to run the GPU’s outlet straight to the upper radiator. As the 5090 would be spitting 600 watts into the loop, I wanted most of that heat to end up in the top radiator that I knew would be capable of dissipating tons of heat. I ran the outlet of this radiator back into the reservoir.

Getting these bits of tubing into place, although it may be soft tubing, was incredibly difficult. I’ll explain why in a bit, but first, let’s finish the loop.

I then ran over to the bottom radiator to the CPU’s outlet. The outlet of this radiator would go to the GPU, but the inlet of this radiator needed a more creative approach to access it.

Using a 90-degree elbow, I was able to run a stretch of tubing in a gap underneath the power supply, running through some cables, up into the main cavity.

Being a stretch that I couldn’t easily measure beforehand, I cut a longer piece so that I could cut it to size before popping the other end onto the outlet of the CPU block.

Cut to size, it fit beautifully and kink-free.

Finally, I cut a piece of tubing to run from the bottom radiator to the inlet of the GPU block.

The space I had to work with here was absolutely tiny, and the more tubes showed up, the more difficult it got to fasten the fittings. Pray for me that there are no leaks.

Leak testing

I popped the leak-tester onto the loop, pumped it up with air, and lo-and-behold – the loop was leaky. And not just a little. I was unable to pump it beyond 0.3 bar, and it would lose this pressure in a matter of 20-30 seconds.

There was good news and bad news. The good news was that I could hear the leak. The bad news was that it was the short tube run that returned the coolant from the thick radiator back to the reservoir.

Due to the magic of rotary fittings, I was able to get the top radiator surprisingly far out of position and could tighten up the problematic fitting. Because the tube run was so short, when I had done up the second fitting on this part, I had accidentally undone the first.

However, this wasn’t the only leak. The loop held pressure better, but it still wasn’t great, and although I couldn’t hear it, I suspected one of the GPU’s plugs may have been the culprit. I had tightened the fitting as hard as possible with the plastic fastener, and yet, the loop was still leaking. I pulled it out, flipped the gasket, but it was still leaking.

The point of these plastic fasteners is so that you don’t over-tighten plugs. Although not so bad here, when tightening plugs in acrylic, you have to be careful not to over-tighten, as it will crack the brittle acrylic material. These plastic tools are meant to break before the acrylic does.

But this wasn’t acrylic. So, I grabbed a screwdriver and gave it an extra shove – which worked. It seems there was something in the threading that blocked the plug from going in all the way. Once I got past that, it easily twisted into the exact same position as the other plug.

I was then able to pump the loop up to pressure, and it looked to be holding it well. I went for dinner, and two hours later when I came back, the pressure had dropped to about 0.4 bar.

Part of this was possibly due to pressure loss in the loop, likely due to microleaks, but another part was a problem these testers are known to have: if you tap them, the needle drops to the actual pressure. I had forgotten to tap it before I left to make the needle drop, so the 0.5 reading at the start may not have been entirely accurate – but with 0.4 after taps and two hours away, I had full confidence in the loop.

Even if there was a tiny leak somewhere, water is thicker than air, and thus less likely to escape, and the loop would certainly not be running at anything close to 0.5 bar anyway. I intended to run the loop hot, but not so hot to generate that kind of pressure.