What I learned building my first custom water loop

This weekend, I've fulfilled a long dream of mine and upgraded my computer to a fully custom waterloop. This is, for a number of a reasons, a complicated process, and outside of general advice, it's difficult to provide an exact guide on how to do this. Custom waterloops are, well, custom. They depend mostly on what computer case you use, and what sort of reservoir and such you've bought. As such, my advice can also only be general.

Plan ahead

Check online for custom watercooling builds in your case. Use those as a guide for radiator and reservoir placement. Sketch ideas out on paper. Measure out the places inside of your case where you intend to place components. Check the your pc case manual, those very often contain info on where you can place radiators and reservoirs.

Some cases are ill-suited for custom waterloops. Consider buying a new case rather than building in an old, ill-suited one. It will save you a lot of pain.

Some cases require modifications. I had to cut into mine with a metal saw to make space for a radiator. Minimal material was removed from the frame, invisible after the case is put back together. I also had to drill into it to place the reservoir. The holes case manufacturers place for reservoirs are best-effort guesses. Unlike for fans, and thus radiators, there are no standards for reservoirs.

Do not rush

Expect a marathon, not a sprint. There will be setbacks. My process, setbacks and all, took me 3 days. And I still fucked up assembling my GPU. The die has bad contact and I'll have to drain the loop, pull it out, disassemble it and put it back together again. A lot of this was also spent waiting for next-day deliveries to show up because I'm dumb and was missing things.

Prefer soft tubing

There are no performance benefits to hardline tubes, and they are a bitch to measure, bend and cut precisely. That 95° angle that was meant to be a 90° is going to be evident immediately, and forever. Soft tubes are forgiving, easy to put into the system and much more time efficient. They also do not require extra equipment dedicated solely to bending hardline tubes. Think about where your build is going to sit. On the floor? Who gives a shit how it looks?

Custom waterloops are all about you, and if you insist, then you do you. Hardline tubes are the endboss of all pc builds. Be ready for a challenge.

Tube sizes

The standard soft tube is 13 mm outer diameter and 10 mm inner diameter, or 13/10. There's a ton of other sizes as well but remember even if the inner diameter is larger, liquid flow improvemets are going to be marginal. Different sizes also need different fittings.

Respect the crink

Soft tubing is a breeze to put into your system, but don't make those corners too tight or it'll crink and cut off flow. Check this especially when you close up the panels of your pc case. Tubing is cheap, comparatively. Don't be afraid to use more than you need.

Money

Custom water loops are pricey. Full copper radiators start at 100€, water blocks are usually hundreds as well, with the tubing, fittings and all it's normal for cooling equipment alone to account for a grand. You're bolting an aftermarket cooling system onto your PC that will turn it into a racecar. A lot of that is finely machined copper. It costs.

Remember the extras

Ya know how I said that I needed to order some extra things last-minute? Thank fuck for Amazon and their fast deliveries. If you live in a larger city, there's also a good chance a specialist computer store somewhere might have what you need.

Leak tester

Those are small air pumps with a pressure gauge. You close of all ports and then pump air into the system, 0.5 bar maximum (!!!), and wait 60 minutes. If the pressure is maintained, congratulations, your system is air- and thus watertight.

Test your individual components before you put them into your case! This way, you know that the components themselves are tight, and you avoid having to pull out a radiator after screwing it in place because you forgot to tighten that one end cap you can now no longer reach. Ask me how I know.

Also test our loop when it's fully assembled. Should you have a leak, divide your loop into two halves and leak test those. Repeat (divide into halves and test) until you have located the leak. If you have tested your comps individually before, it's going to be a radiator fitting you forgot to tighten or your reservoir top 99% of the time. Have a book or a podcast ready because this is a long process with lots of downtime.

Motherboard 24-pin jumper plug

These nifty little things are incredibly cheap and useful. After you wire everything up, you want to fill your reservoir and turn on the pump, but obviously you do not want to immediately electrify your entire system. So you pull the 24-pin motherboard cable of your motherboard and put the plug into it. It bridges specific pins, tricking your power supply into thinking a motherboard is connected. This way your pump turns on without the rest of your system. Once the water is circulating and not catastrophes have occured, you can turn off your power supply and plug the mobo back in.

Common advice

This is advice that's often repeated in watercooling circles for beginners. If you're seriously considering doing this, you will likely already have stumbled upon these. I'm adding these just for posterity.

Do not mix aluminium and copper/brass

Cheaper watercooling components are often out of aluminium while pricier ones are out of copper. You do not want both in your system as they eat each other through galvanic corrosion. If your cooling blocks for the GPU and CPU use copper (they very often do), the rest needs to be out of copper or brass as well, fittings included!

Buy more fittings than you think you need

Remember, per tube you'll need at least two! Check that they have O-rings, as those provide the seal.

Put a drain port into your loop

You should generally drain and flush the loop at least once a year. This will be a lot easier if on low points you have faucet you can attach a tube to and open to drain it. Pulling the loop back apart is generally the last thing people think off when building a custom loop for the first time, so it's useful to know.

Consider quick disconnects

Quick disconnects are special fittings you can put into a tube or attach directly to a port. You can then pull them apart with minimal or no leakage of your cooling fluid without having to drain your loop. Really useful for example the GPU, which tends to be the component that's swapped out most often.

Use cooling fluids over distilled water

Obviously no fucking tap water, ever! But lots of folks also gravitate to distilled water. Cooling fluids like what Alphacool or Aquacomputer make have extra stuff in them, like corrosion inhibitors and biocides that prevent algae build up. You can also mix these yourself if you can get the inhibitors and biocides concentrated but if you're on that level I don't think you need this guide anymore.

Also, colored liquid fucking sucks. Unless you want to pull apart your water blocks and clean them with a toothbrush, use clear liquids. If you want fun colors, put RGB into your case.

120 mm of radiator length per 100 W of heat generation

The two components generating the most heat in your PC are likely the CPU and GPU. Check the specs of those to see how much heat they generate. This number is generally known as the Thermal Design Point (TDP). Radiators come in many sizes fitted to fan sizes, mostly in multiples of 120 or 140 mm, but running this calculation gives you a baseline for how much radiators you need. More is always better! Fit in as many radiators as you can into your case, but if your case can't fit the number of this calculation then you need to look for a bigger case.

Knowing the TDP is rarer for GPUs, you can also use board power or power draw as a substitute. We're doing napkin math here, no need to be precise.

Example:

CPU: 170 W

GPU: 300 W

-> round up to 500 W, which means 5 * 120 = 600. A 360 mm radiator fits 3 120 mm fans. You'd need 2 radiators with 3 fans each to cool your system adequately.

Alternatively, a 280 mm radiator fits 2 140 mm fans. You'd need 3 of those to cool the system.

Radiator thiccckness

Radiators come in different thicknesses. Since what dictates a radiator's ability to dissipate heat is the total surface of it's fins, increasing the thickness improves cooling ability. However, most PC cases, even full towers, are practically limited to 45 cm rad height at most.

Noise

A big motivation for doing this was noise. Cooling everything with a custom loop means that I've lost the 2 fans on my CPU air cooler and the 3 fans on my GPU. What remains are the case fans only, 2x180 mm ones and 3x140 mm. Those can now run at dramatically lower speeds (10% fan speed at idle, ramping up much more slowly) for a nearly silent build even under full load. The pump and reservoir combo I've chosen are isolated from the pc case through rubber standoffs which means that the pump, even when at 100%, runs dead-silent.

Chasing diminishing returns

Switching to a custom loop alone is a massive bonus to the computer's ability to be cooled, because water is a much more efficient way to move heat than air. Case radiators also have much more volume than the heat sinks on your GPU and CPU right now, improving the cooling further.

Once you step into this world, the choices open to you are staggering. Delidding the CPU. Using liquid metal instead of thermal paste, etc. etc. Unless you're planning on overclocking your system, there's no point to doing any of those things that are actively dangerous.

Liquid metal buys you a couple of degrees °C at best, at the cost of being dangerous and difficult to apply and even a tiny escaped drop having the ability to short and fry your GPU for good.

Delidding your CPU is only useful if you plan to overclock. I did it, but only because the company Thermal Grizzly sells delidded CPUs and a fitting water cooling block. If you're doing it at home, the investment is way too large to make sense. Delidding also requires liquid metal afterwards. See paragraph above for that.

If you're in this just because you want a high performing system at less noise, then using a PTM material instead of thermal paste is going to be good enough.

All of these improvements lower temperatures of your components. Delidding the CPU and cooling it directly buys you something like 20°C under load. But the thing is, a good water cooling loop can absolutely cope with a high performance CPU running at 100 per cent. With the IHS on it'll just push 80°C instead of 60°C.

Functionally, there's no difference if the CPU runs at 60°C or 80°C. The only time it matters if if you're over clocking and through that causing the CPU to approach its thermal limit. Then dropping it by a few degrees makes sense.

If not? Skip them.

I hope these help people. Feel free to ask any questions!