How to Build a PC with a Hardline Water-Cooling Loop

Updated 9/17 with written instructions. 

We’ve got a video and written walkthrough below to help you get your own custom water loop set up. If you already know all about water cooling, you can skip right ahead. If you’re looking for a bit more info first, we’ve got a quick explainer that should catch you up:

What are water cooling loops? And why use water over air cooling?

The short answer is that water cooling is a method of lowering the temperature of a build’s processor that offers (generally) better cooling and more customizability than traditional air cooling, doubly so when building a fully custom loop. 

The longer answer is that there are three main ways to cool your CPU:

• Air Cooling
• All-In-One (AIO) Loops
• Custom Loops

Air cooling, basically a fan and heatsink, is the most common, as it’s frequently found in pre-built PCs and, barring a few prototypes, it’s used in every laptop. And while air cooling has undeniably improved a lot in recent years, putting it neck-and-neck with water cooling loops for most use cases, its customizability is limited to orientation and, in some cases, RGB lighting. Air coolers can also struggle to keep high-end processors cool during heavy workloads.

If you are using water cooling, it’s probably an AIO. AIOs, or All-In-One loops, are just that: every part of a water loop condensed down into a single sealed component. An AIO will combine the pump, tubing, and radiator (usually leaving the radiator fans off for installation purposes) into one easy-to-install package. They also offer a bit more cooling potential than traditional air coolers and a bit more customizability, as you can choose the radiator position within your case and many have customizable LCD screens. 

AIOs are also my go-to when it comes to building a PC, as, if you’ll allow me a bit of editorializing, I think they’re just plain neat. Even if I never push my computer to the point where an AIO is required, there is something inherently interesting about the phrase “oh yeah, my PC is water cooled.” But “Oh yeah, my PC is water cooled. I designed and built the whole thing myself” is even more interesting.

And now here’s the twist: not only are custom loops the most customizable, but you can even set them up to cool other components as well, like your GPU, all on a single loop. A loop can look like anything, run through the case however you want, and cool whichever components you choose. You could even have it burst through the side panel, so long as you have the time, space, and know-how.

Custom loops offer the best cooling potential and most customizability of the three most common cooling solutions; but now that you know the why, the question is how.

How to Build a Custom Hard Line Water Loop

So how do you build a custom water loop? With lots and lots of planning and patience. I highly recommend checking out Alex’s guide to get a good feel for what goes into building a Custom Loop PC. But if you, like me, prefer to read your instructions, good news: Alex also walked me through every step of the build in great detail so I can provide the step-by-step guide to hardline tubing.

I’m never visible in the video, but you can imagine me sitting juuuuust off camera.

Before you build:

With most PC builds, there aren’t many safety concerns beyond an anti-static band, if that. With hardline tubing, especially carbon fiber hardline tubing, there are some key safety issues to consider. 

First is the method of cutting the tubes. While some tubing can be cut with common household scissors, others will require more advanced tools. We used a table saw to cut our carbon fiber and had to take precautions. As carbon fiber is incredibly toxic to breathe, we recommend N95 masks, like those you would use for painting or sanding projects, to keep dust out of your lungs. Also safety glasses can go a long way to keep sharp, plastic shavings out of eyeballs.

Depending on your build, you may also be sanding. Again, N95 masks are incredibly helpful to avoid accidental inhalations and latex gloves can help keep your hands clean; carbon fiber will stick to your fingers and you don’t want to grab a burrito with those hands.

Wear gloves, folks. Photo: Sean Mekinda 

• A table saw
• Sand paper (we used 120 grit, 220 grit, and 320 grit)
• N95 painter maks
• Disposable latex gloves
• Safety glasses
• Distilled water

Once you’ve got your safety gear and tools ready, it’s time to start building.

1: Sketch out the plan and pick up parts

If you’ve built a PC before, you know that before doing anything else, you have to pick out your parts. A hardline tube build works much the same way, but you’ll also need to account for those tubes. That means drafting out a rough sketch for how you want the build to look.

Photo: Alex H.

This first sketch is mostly to get a feel for how many pipes the build will need, how long each will be, and how much space the case has. Remember that, at bare minimum, you’ll need to create a loop connecting the pump to the radiator to the reservoir and back; that's going to be at least four pipes (though depending on spacing needs, one pipe cut into three sections may work). 

Traditional hardline tubing can be heated and bent into shape (though be careful not to overwork it) for a fairly standard two-pipe setup. But if you’re using carbon fiber like we did, it can’t be bent and you’ll need to work with angled fittings, each junction representing another cut.

The good part about this step is that it’s very flexible. None of the sketches are set in stone and you can always pick up more fittings or tubing if needed. Importantly, however, it provides a baseline for your build that can help save a few trips to the store.

A note: Some say that flow orientation matters, arguing that if you’re coming from the hotter component (the GPU) to the cooler component (the CPU), the water will be hotter and not cool as efficiently. However, cooling fluid will quickly equalize in temperature, so if there is a difference, it will be incredibly minor; all that matters is that the fluid has a clear directional flow.

2: Run a post test before putting the PC in the case

Photo: Keving Liu 

3: Assemble (almost) everything in the case

Once the PC has a confirmed post, it's time to start getting the build installed. This section is more-or-less just a traditional PC build; the motherboard, processor, RAM, fans., And if you’re not water cooling the GPU, the graphics card can also be installed as usual.

Photo: Kevin Liu 

Additionally, you’ll want to get the pump (the piece that goes over the CPU; don’t forget thermal paste!), reservoir, and radiator set up, as well as any fans that attach to the radiator.

Be sure to attach all cables.

3a: Assemble and install GPU water block (if applicable)

If you’re not including your GPU in your loop, skip ahead to step 4b.

Adding a GPU waterblock is remarkably easy, though un-shelling a GPU can seem intimidating. You’ll just need to find the screws that hold the fan shroud on and remove them; they’re usually fairly easy to spot. 

Once the screws are out, the shroud should pop right off. If it doesn’t: first, check to make sure all screws have been removed. If all screws have been removed, grab a spudger and gently lift the shroud from the PCB. When it’s all said and done, you should be left with something like this:

Photo: Kevin Liu 

While you should follow the documentation included with your water block for detailed instructions, the general idea is to use the (usually) included thermal pads on either side of the PCB to sandwich it between the waterblock and backplate. Once everything is screwed into place, simply slot it in the usual PCIe slot and connect the power cable.

3b: Cable management!

Cable management is super important to keep any build looking nice, but doubly so with water-cooled builds. There are a lot of pipes, wires, and pieces that go into a custom loop, so managing the cables currently in the PC before installing any pipes is a must. It’s way easier to install a foot-long tube when you’re not fighting a loose SATA cable at the same time. 

More and more cases contain specific channels to make cable management easier than ever, but zip ties or velcro straps work wonders and have been long-time staples of the PC builder.

4: Revisit your sketched plan and make adjustments

With all non-tubing parts installed, it’s time to revisit the sketch. Rather than just estimating space, it's time to take accurate measurements, ensure that no components juts out unexpectedly to force a reroute, and check your clearances. More than likely, there is something you’ll need to adjust; maybe a fan sticks out more than expected or you have more clearance for a better run. One important thing to remember is that pipes take up space -- if your build has them crossing over one another, make sure you have the clearance needed so your pipes won’t collide.

Photo: Kevin Liu 

Once you have exact measurements and confirm everything should fit as expected, it's time to start working with tubing.

5: Prepping the tubing

Start by measuring and marking needed cuts on the tubes, labeling pipes as you go (IE: CPU in, CPU out) with masking tape. There will be a lot of tubes cut and you don’t want to spend the build portion wondering if you put the right sized tube in the right place, or if the one that was slightly longer was actually supposed to go there. 

Once things are measured out, it’s time to start cutting.

For this build, we used carbon fiber tubing, so, unlike traditional hardline tubing, it could not be heated and bent into shape. However, these steps very much apply to any flexible hard line tubes that need cutting.

Photo: Kevin Liu 

When cutting tubing, always be sure to undercut, leaving an extra 16th of an inch or so beyond your measurement; you can always take more tubing off, but you can’t add tubing back on if you overcut.

That extra bit of tubing will also be sanded off almost immediately as well, as a smooth tube is crucial to prevent leaks. An inadvertently-sharp tube can damage the o-rings in the couplings, leading to a seal that isn’t as tight as it should be. Start with the lowest grit sand paper -- for us, it was 120 -- and work your way up, smoothing the opening of the tube with each pass.

Photo: Kevin Liu 

Once your tubes have been cut and sanded, run distilled water through them to clear out any remaining shavings. Leftover shavings can create a number of problems, from blocking pipes to ruining pumps to even bacterial growth. Bacterial growth is also why we use distilled water, as it has been purified and with no additives that could cause buildup or growth. 

6: Install tubing and fittings

"Measure twice cut once," is the adage, but with a hardline build, you might want to measure a third, fourth, or even fifth time. 

Once everything is cut out, measure one last time by lightly fitting everything together. Keep in mind that a bit of the piping will be physically in the fittings, so it might look a little long, but if everything connects well enough, you’re good to start assembling; you can always sand more off if needed.

Your fittings may work slightly differently, but the basic principle should be the same. We used Alphacool, which feature two main couplings: L-connectors and right-angle. Right angle couplings are threaded on both sides, so they can be used with screw-on fittings to join two pipes at -- as the name implies -- a right angle. Our L-connectors came with a threaded male end, helpfully indicating which side needed to be attached to our water blocks. The other, unthreaded side is for a fitting and, of course, piping.

An L-connector next to a water block. A right-angle connector can be seen on the left side. Photo: Sean Mekinda 

Connecting a pipe to a fitting is remarkably simple. Just unscrew the fitting and pull the o-ring out. Slide the pipe into the base of the fitting, then slide the o-ring on, and then the top of the fitting. Hand-tighten that fitting, and the pipe is secured. Hand-tightening will give it a tight seal without the risk of overtightening and cracking the pipe, which can lead to leaks. 

Photo: Kevin Liu 

Connect all fittings and pipes according to your sketch. If a pipe is still too long, sandpaper can be used to quickly grind down any extra.

7: Testing

Once your pipes and fittings are installed, give them all a once-over to ensure that they are sufficiently tight with no potential for leaks. Now it’s time for the scary part: testing the build. 

However, don’t go plugging it in just yet. We’re going to do a test without power first, and there are two ways to do this.

The first is quicker and easier, but leaves some room for error. You can pick up one of these leak testers and use it to verify the seal on the loop. Simply connect it to the loop and pump. If the pressure remains stable, you should be good to go. 

The second is a bit harder but 100% confirms there are no leaks and gives your system one last flush before finalizing. However: we recommend laying down a (de-staticked) cloth or towel over any exposed parts. 

Photo: Kevin Liu 

Using the fill port, slowly fill the reservoir with distilled water, letting it naturally flow through the loop. You may need to tip and tilt your PC a bit to test all pipes, but if there are no leaks for this test, there are no leaks, period. The PC may need to be turned on -- but just let it idle -- so the pump can get the water to get the water to fully flow. Drain the distilled water from the loop and get ready to power up.

8: Filling the reservoir and finishing touches

The final step of any hardline build is to fill it up. Using the cooling solution of your choice, fill the reservoir as much as possible. Then, once the reservoir has been sealed, boot the PC and let it run. There will likely still be air left in the pipes, and letting the PC idle will force the air into the reservoir. 

Once it seems like any bubbling has stopped, turn the PC off, open up the reservoir, and fill in any space that may have opened in the reservoir -- as a rule of thumb, you want as much liquid as possible. This step should only need to be done once, but keep an eye on the reservoir. If it starts to lower, you may need to add a bit more cooling liquid.

Photo: Kevin Liu 

From there, it’s just about setting up the PC how you like it! Close up the case, connect peripherals, install your OS, and then step back and admire your very own, custom-built water-cooled PC.

Or you could save yourself several days worth of effort and bring your PC to Micro Center. 

Option B: Let Micro Center do it for you

A hardline PC is a lot of work to put together. Thankfully, knowledgeable experts like Alex are there to help. We have a wide range of build options, from traditional air cooling all the way to complex hardline PCs. So, if you want a custom PC but want to save on time, stop by your local Micro Center. We’re happy to help you put together the PC of your dreams.