Sidenote: The Nerve-Wracking Tedium of Finally Flushing My Watercooling Loop for Maintenance

On Monday this week, it was time.

New coolant had arrived in the mail, I had a fresh roll of shop towels, my excess tubing and fittings, some distilled water, and scissors. I needed to do something I had feared for a while – regular watercooling maintenance.

Over the last 10 months, I’ve chronicled my first full custom-loop watercooled PC journey, from the first thoughts to the build up to having moved with it, but there was still one frontier left to chart with it – draining the loop to replace coolant.

My current coolant was fine enough, and 10 months was early (clear coolant can last up to two years while opaque coolants and fancy nanofluids are usually on 6 month schedules), but I had a few concerns. Firstly and most pressing, the tube length running from my last radiator in the loop back into the return on my water reservoir was kinked and the fold in the tube was getting worse with time. Not to a point of complete flow restriction, but the fact that it was continuing to fold in on itself was troubling. I had attempted an improv solution with some Googling of tying zip ties around the kink to try and open the inner tubing up for more flow, but it hadn’t really noticeably changed anything, looked uglier, and in the process of doing it, I had noticed the inner wall of the tubing at the kink was yellowing and looked like it might be thinning.

Secondly, I build the original loop with purple coolant and gold fittings as homage to Shadowbringers, the current Final Fantasy XIV expansion for another…3 weeks as I write this. I was starting to want a change, but I couldn’t just switch the LED colors to something totally different because the coolant was still that dark, deep purple. After swapping the kinked length of tube, this was my next pressing concern.

Thirdly, while Corsair swears in the documentation that you do not need to flush their radiators, as they come pre-cleaned from the factory, the hours of watercooling videos I watched researching the build told me that it was likely that components would still have bits of factory gunk in them – mostly the radiators, whose soldering process of merging tubes to cooling fins leaves solder flux in the tubes. Couple that with the normal plasticizer leeching from tubing that soft tubing falls prey to, and my coolant was likely to have bits of gunk in it.

But I didn’t want to disassemble the whole system and dry everything out to refill it over a day or more of time. So I instead went for a flush. This works just fine for maintenance with no part swaps, and just involves draining the fluid as much as possible, adding distilled water to dilute and further flush the old fluid, and then, once that is done, topping off with the new coolant and running. I had ordered Corsair’s new XL8 coolant (it is the same formula but a new manufacturer, supposedly, as the original XL5 was made by Mayhems, a watercooling company, and then rebadged) in fully clear. I still used coolant and not just distilled water as the coolant has biocides and anti-corrosion additives, and the cost to order these additives was about the same as just ordering a liter of premixed coolant, so off I went.

The tools of the trade, ready to go

The first part was nerve-wracking immediately. When assembling the system the first time, I had dropped my drain valve on the floor and broken the handle on it, leaving only half of it on. A stop plug inserted after the ball valve keeps things nice and sealed, but what I hadn’t seen is that the ball was not fully closed because of the broken handle. When I first opened the stop plug, I got about 8 drops of purple drink on my desk and in my PC case. Yikes!

Luckily, the front of the case is an open radiator area with no components where the leak occurred, so a quick wipe up and I was back to normal, save for my heart rate. The ball valve was easy enough to mate with a fitting and length of tubing, so I set out on the tedious process of dropping the tubing into my catch bowl, opening the ball valve, and letting the first bit of fluid out.

This process was monumentally easier because I read up and installed a drain port on my system, using an elbow fitting, a tiny length of tubing, two compression fittings, and the ball valve fitting. Had I not done that, a drain and refill would have comprised a lot more tasks including flipping my system on its side to open a side port on the pump and it would have been a lot more harrowing. Thanks to the extra fittings and forethought, though, I was able to run a drain tube and a longer refill tube, keeping me from having to use the squirt bottle inside the case, which always gets me sweaty and makes me incredibly nervous.

The process involved the most tedious thing ever, opening the drain, closing it, topping off with distilled water, running the pump, opening the drain, shutting off the pump, closing the drain, and then repeating that process 8 times (no joke) until all the purple Grimace juice had left my system. There was still a pretty decent amount of distilled water in the system, with the tubing around the GPU and CPU all full of it, but the color was gone and my reset was a success to that point.

I very carefully checked the tube that was kinked to confirm it was empty, and was able to successfully extract it. Here it is next to a fresh piece of tubing for the contrast!

Cutting a clean length was tricky, as the bend is fairly tight and compact, so it needed to be short enough to complete the run without slop to fold over on itself, but also not so short that it couldn’t snug down tight over the barbs of the compression fittings. It took me, no joke, about 20 minutes of cutting and test-fitting until I had a length of replacement tube that was workable.

With that done, it was easy enough – close up the drain loop, get the tubing out of the valve and the stop plug back in, top off with the new coolant, and then let it run just the pump for about 30 minutes to get air out while I shook the case gently in different directions until everything settled in with no gurgling pump or cascading water sounds.

Firing up the system didn’t show any immediate deviations in temperatures – a couple intense minutes in New World still heated things up a lot and the liquid temperature was around the same. It worked the same, so I wasn’t disappointed, but I did want to try and find a way to make things better, so I read up on what settings I could change to influence things. It turns out that running the pump at 100%, while good enough in theory, meant that water was moving through the radiators too fast to be cooled much, which led to the gradual climb I saw in New World. I backed the pump speed down to 60%, and I had exactly the tradeoff I wanted – slightly warmed component temperatures (because the water removing the heat from them spends longer in the waterblocks for those parts) but much cooler liquid. My part temps were still good and low, so I was happy to make that trade, especially because cooler water means cooler exhaust which means my office area stays cooler and I feel less hot for it!

So I made the final change, switching LEDs over to get a nice bright “end-of-the-world” orange for Endwalker, and hooray – job done!

Overall, it was pretty easy but definitely still stressful – watercooling and the ways in which a system can be irreversibly damaged if you mess it up still gets my dander up – but I’m glad to have played around with it and removed what could have been a genuine problem later on in that stupid kinked tube.

Below, I’ve included an affiliate link to Amazon to purchase some of these products if you so desire. As an Amazon Associate I earn from qualifying purchases. (Corsair’s website does direct sales and can often be cheaper so check them first!)

Corsair Hydro X Series XH305i Hardline Water Cooling Kit with/incl XC7 CPU Water Block, XR5 360mm Radiator, XD5 Pump Res and iCUE QL120 RGB Fans


8 thoughts on “Sidenote: The Nerve-Wracking Tedium of Finally Flushing My Watercooling Loop for Maintenance

  1. Since I am super paranoid about liquids and electronics (it comes honestly) I’m pretty sure I would remove the components and then do the thing. Of course, if I were to do water cooling it would be an AIO system that makes it a lot simpler to do so.

    I’m actually considering that, BTW, but I didn’t realize that the coolant needed to be flushed / changed on occasion, so now I’m dithering again. Well done, sir, well done. 😀

    Liked by 1 person

    1. It took me a long time to come around on watercooling, and it is definitely still a marginal improvement for the money spent, but it has been a fun learning experience and with the right precautions, the (very understandable) paranoia of water and electronics mixing is easy to minimize!

      With the first swap of fluid done, I’ll probably let it be for 2 years now!


      1. Oh man, in my last build I almost waited for this Asus cooler that was the first one with a display on the CPU block, but the cost was so high that I couldn’t justify it. Now there are all kinds including NZXT with round screens, the Corsair one, a couple of Asus ones, and more coming!


      2. Yeah, I already have a lot of the Corsair RGB stuff already (RAM, fans, kb, etc) so this folds in nicely and hopefully doesn’t require yet-another-mostly-functional-tray-tool.

        Liked by 1 person

  2. Every time I think “aw, it can’t be that bad” when I watch a video of Jay from JayzTwoCents doing a custom watercooling installation, I remind myself that I was nearly electrocuted working on my cooking range last year. That usually snaps me back to reality.

    Liked by 1 person

  3. If there’s one reason remote gaming services like Stadia or GeForce Now will ever become mainstream it has to be this (well, that and the insane price-hiking of components, of course, but that’s a variable, not a constant.). The closer things like maintaining watercooling systems get to becoming normative, expected behavior for home PC owners, the more niche that market will become. Let someone else have the trouble and the worry and just pay a subscription to access the games through relatively inert hardware that you just have to switch on and off. And at the current subscription costs, you could sub to two or even three different remote services for a decade for the cost of a new gaming PC.

    Hmm. I think I might be talking myself into something…


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