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

Because I custom-cool PC’s fairly frequently, at some point in the past I’d made a draining hose. This is quite simply a hose that attaches to a G3/4’ port of your choice, usually one at the bottom of a loop or where you can easily get an air-bubble to appear.

I’ve found that simply opening a custom loop and letting water pour out into a sink leads to uncontrolled flow, which can lead to a big mess, and that a lack of control can lead to coolant entering the PC in places where it isn’t supposed to be.

The point of this hose is so that I can open and close the drain valve easily, and hose the coolant into a bucket lower down on the floor without making a mess of things near the PC.

First, we flush the loop

Because these are all new components, the first thing I want to do is give the loop a few flushes. Technically, you should do this to the radiators before mounting them, but I just give them a blast with compressed air in one of the ports, letting it out the other, which gets rid of most of the debris, if there even is any, without giving you drippy radiator during install. That’s also what they do in the factory, and why they install the plastic caps – to stop dirt ingress.

The flush here is mostly for peace of mind, to get rid of any oils and micro-debris that could eat away at finishes and eventually lead to clogged blocks. Though honestly, I doubt it really matters – especially in this system which will be getting dismantled in a few days.

Regardless, demineralized water doesn’t cost much, so I poured some into the loop, topping it up and cycling the pump until it was mostly full, and then used the drain hose and drain valve to clear most of it out.

If a loop is easy to fill and drain, I do this a couple of times, but this loop is more difficult. Due to the small size of the reservoir, filling it is quite tedious, as you can only add a tiny bit of fluid, and once you run the pump, it’s gone almost immediately. You don’t want to run a pump dry, and that meant starting and stopping the loop many times before the loop was full.

Consequently, what I opted to do instead was fill the loop fully, and then crack the drain valve, but only a tiny bit. Then, I kept the loop running, while it drained slowly, and squeezed the filling bottle just enough to keep the reservoir topped up, adding in water at roughly the same rate that it drained out.

This dilutes whatever dirt may be in the loop, and once I worked through about three liters of water, I drained the loop fully.

With the loop empty, I removed the drain hose, popped the plug back onto the reservoir, and filled the loop with clear coolant.

A time-consuming process, mostly

With a big PC that has a big reservoir, filling is easy: you fill the reservoir, and run the pump till the reservoir is almost empty. Then, you refill and repeat two or three times until the loop is full.

With this smaller PC, it’s a bit more complicated. The reservoir is tiny. I’m talking – less than two shots of espresso. I weighed it out, and this loop took about 850 ml of fluid. So, much of the filling I did by opening ports on the radiators to fill them up, only topping up the reservoir at a later part of the process.

Despite this, I had to top up the reservoir at least a dozen or more times, and because the filling port is right in the path of the return line, once the loop got fuller, I had to close the port while cycling the pump to stop water from sputtering everywhere. This of course, became very tedious.

Moreover, large air pockets could only be removed by picking the PC up and tilting it in all sorts of ways, even upside-down. With a big reservoir, you can just let the air move that way in due time, but because this reservoir is so tiny, if a bigger air pocket were to move to the reservoir, the chance of the pump running dry would be very high, so they all had to go.

Thankfully, because it’s a Mini-ITX PC, bleeding the loop is easy. Once full enough, close it all up, run the pump, and pick the PC up, shake it, tilt it, shake it some more, and really get all the air bubbles into the reservoir.

Top that up, repeat a couple times, and the system is bled and free of bubbles, suddenly running it much quieter. With a big PC that you can’t simply pick up and shake in all directions, it becomes a waiting game, and it can often take two to three days, or sometimes up to a week to bleed most of the air out of the loop. One of my other PCs still has a bubble near the top of the loop that I can see in the tubing, and it’s been there for years.