Choosing the Best Coolant for Your Custom PC Liquid Cooling Loop
Hey there PC enthusiasts! If you‘re thinking about building a high-performance gaming rig or workstation with a custom liquid cooling loop, one of the most critical decisions you‘ll need to make is what type of coolant to use. The coolant is the lifeblood of your cooling system, transferring heat away from components like your CPU, GPU, chipset, and voltage regulation modules to keep everything running cool and stable.
But not all coolants are created equal. Choosing the right one involves analyzing a variety of factors including thermal performance, fluid dynamics, material compatibility, corrosion resistance, and even aesthetics. Even a small difference in coolant composition and quality can have a big impact on cooling efficiency, stability, and the longevity of your loop.
As a computer hardware geek who has built dozens of custom liquid-cooled PCs over the years, I‘ve spent countless hours researching, testing and comparing different coolants to find the best options. In this in-depth guide, I‘ll share what I‘ve learned to help you make an informed decision for your build. We‘ll dive deep into the science of coolants, examine the key criteria to look at, analyze and compare some of the top products on the market, and provide tips for maintaining your coolant loop. I‘ll also explain the differences between using the CPU_FAN vs CPU_OPT headers to power your pump.
Whether you‘re a first-time builder or a veteran enthusiast, by the end of this article you‘ll have the knowledge needed to choose the best performing and most reliable coolant to keep your high-end PC running cool. Let‘s dive in!
Liquid Cooling vs Air Cooling
Before we look specifically at coolants, let‘s quickly recap the benefits of liquid cooling vs air cooling. High-end PCs generate a lot of heat, especially when overclocked. Liquid cooling provides significantly better thermal conductivity and heat capacity compared to air.
A liquid cooling loop uses a pump to cycle the coolant through water blocks mounted on hot components like the CPU and GPU. The heated fluid then flows to a radiator where heat is dissipated. This allows the coolant to continuously absorb and expel heat.
The main advantages of liquid cooling include:
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Lower temperatures: Liquid transfers heat much more efficiently than air, allowing you to maintain lower and more consistent temps.
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Better overclocking: The improved thermal headroom lets you push clock speeds and voltages further for better performance.
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Quieter operation: You can run fans at lower RPMs since the radiator has more surface area and the liquid is doing most of the work.
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Improved aesthetics: Custom hard tube or soft tube loops with colored coolants can look striking compared to bulky air coolers.
For most casual users and gamers, a good air cooler is more than sufficient and more practical. But if you‘re an enthusiast building a powerful high-end rig, especially with an i9/Ryzen 9 CPU and a power-hungry GPU, a custom liquid cooling loop is well worth considering.
Understanding the Properties of Liquid Coolants
Not all coolants are just different colors of the same formula. There are several important physical and chemical properties that affect performance, reliability and compatibility. Here are the key characteristics to be aware of:
Thermal Conductivity
This measures how effectively the liquid transfers heat. The higher the thermal conductivity, the better the coolant will be at moving heat from the water blocks to the radiator. It‘s measured in Watts per meter-Kelvin (W/mK). For PC cooling, you generally want a thermal conductivity of at least 0.6 W/mK.
Specific Heat Capacity
This refers to the amount of heat energy required to raise the temperature of the coolant by 1°C. Higher specific heat capacity allows the liquid to absorb more heat while maintaining lower temps. It‘s measured in kilojoules per kilogram Kelvin (kJ/kgK). For PC coolants, look for specific heat capacities of at least 3-4 kJ/kgK.
Viscosity
Viscosity quantifies a fluid‘s resistance to flow. Lower viscosities flow more easily, which improves your pump‘s efficiency and reduces the load on it. This allows you to run the pump at lower speeds while still maintaining good circulation of coolant through the loop. Avoid coolants that are too thick or syrupy. Ideal PC coolant viscosity is under 2 centipoise (cP) at ambient temps.
Corrosion and Biological Growth Resistance
It‘s important that your coolant has additives to prevent corrosion of the metal parts in your loop. Over time, corrosion can degrade performance and cause component failure. Untreated water can also promote biological growth which can gunk up the loop. The best coolants use anti-corrosive and anti-fungal ingredients to maintain reliable performance and extend the longevity of your cooling system.
Electrical Conductivity
While pure distilled water is not electrically conductive, the anti-corrosion additives in coolants generally are. It‘s important that the conductivity is low enough that it won‘t cause problems if small amounts of coolant leak onto sensitive components. Most coolants have conductivities under 2 millisiemens per cm (mS/cm) which is considered safe.
Material Compatibility
Make sure the coolant you choose is fully compatible with all the materials in your loop. Some coolants can cause plasticizer leaching in soft tubing or react poorly with certain metals. The best coolants are extensively tested to be compatible with common tubing materials like PVC, silicone, and EPDM as well as metals like copper, brass, and nickel.
Colored Coolants and Transparency
PC builders often prefer colored coolants to enhance the aesthetics of their machine. You can find coolants in a rainbow of colors from red, green and blue to purple, orange, white and even UV reactive. Consider how the color will look with your build‘s color scheme and lighting. Also decide if you want a translucent or solid opaque look.
Transparent coolants let you see the fluid dynamics in action and keep an eye out for contaminants or blockages. They can also create cool visual effects as they refract light from LEDs or UV lamps.
Opaque nano-fluids, on the other hand, provide a striking solid color and can help hide any residue or buildup in the tubes. They tend to have a "milky" or "pastel" look. Just be aware that some opaque fluids have a higher risk of gunking up or separating over time compared to transparent ones.
The color is really a matter of personal taste, but make sure the dye is stable and won‘t break down, stain components, or fall out of suspension over time. High quality dyed coolants use non-reactive organic dyes that stay uniformly mixed.
Premixed vs Concentrate
Some coolants come as ready-to-use premixed liquids, while others are sold as concentrates that you mix with distilled water. Concentrates can be more economical in the long run and allow you to fine tune the mixture. For example, you can dilute the coolant more for better flow rate or run it more concentrated for better performance.
Premixed coolants are more convenient as you don‘t have to worry about getting the ratios right. They‘re ideal for beginners or those who want a grab-and-go solution.
Evaluating Popular Coolant Brands and Products
There are a number of brands that cater to the enthusiast PC liquid cooling market. Here are some of the most popular product lines and how they compare:
EK-CryoFuel
EK-CryoFuel is one of the best selling PC coolants and for good reason. It uses an ethylene glycol (EG) based formula with anti-corrosive and anti-biological additives, providing excellent thermal performance and long-term reliability. It‘s available in both clear and colored variants in premixed 900mL and 1L bottles as well as 100mL concentrates.
I‘ve been running EK-CryoFuel clear in my main gaming rig for over a year with no issues. Temperatures are great and I‘ve had zero buildup or discoloration. I also really like the EK-CryoFuel Solid line for projects where I want an eye-catching opaque look. The colors are vibrant, and I‘ve found it to be very stable with no separation or sedimentation.
Thermal Conductivity: 0.78 W/mK
Specific Heat Capacity: 3.56 kJ/kgK
Viscosity: 1.8 cP
Thermaltake P1000 Pastel Coolant
The P1000 Pastel line from Thermaltake is another excellent choice if you‘re looking for an opaque coolant. It uses a non-toxic propylene glycol (PG) based formula with vivid colors and a unique "pastel" look. The thick nano-fluid maintains its suspension very well and has one of the best thermal conductivities on the market at 0.92 W/mK.
The reason I really like Thermaltake P1000 Pastel is the balance of thermal performance, aesthetics, and overall reliability. Gunking and staining are minimal even in long-term use, and the candy-like colors make any build pop. It‘s available in 1L premixed bottles in blue, green, orange, purple, red, yellow, and white.
Thermal Conductivity: 0.92 W/mK
Specific Heat Capacity: 3.4 kJ/kgK
Viscosity: 1.7 cP
Mayhems X1
Mayhems is one of the OGs in the PC liquid cooling industry, and their X1 line has a stellar reputation amongst enthusiasts. It‘s an EG based coolant that prioritizes performance and reliability. The triple-inhibitor anti-corrosive package is one of the best in the business for preventing corrosion and growth.
I‘ve used Mayhems X1 in a number of client builds and it has never let me down. Flow rate is excellent, and it has one of the lowest electrical conductivities for a coolant at under 1.5 mS/cm. If you‘re looking for a tried-and-true high-performance coolant and aren‘t as concerned about crazy colors, Mayhems X1 should be at the top of your list.
Thermal Conductivity: 0.81 W/mK
Specific Heat Capacity: 3.7 kJ/kgK
Viscosity: 1.5 cP
PrimoChill Vue
PrimoChill‘s Vue line gets a lot of attention for its striking pearlescent visual effects. These semi-translucent coolants contain reflective particles that create mesmerizing swirls and shimmers as they flow through your loop. They‘re definitely a top choice if you want a serious wow factor.
Performance-wise, Vue is solid but not incredible. Its thermal conductivity of 0.65 W/mK is on the lower end of the scale. It also requires more diligent prep and maintenance to prevent the particles from falling out of suspension. I don‘t recommend Vue for your main workhorse rig, but it‘s great for show builds, display PCs, or modded consoles.
Thermal Conductivity: 0.65 W/mK
Specific Heat Capacity: 3.2 kJ/kgK
Viscosity: 1.9 cP
Koolance LIQ-702
If you‘re looking for the absolute best thermal performance at any cost, Koolance LIQ-702 is in a league of its own. It uses a Zinc oxide (ZnO) nanofluid that provides a whopping 1.12 W/mK thermal conductivity. The extremely small nanoparticles remain uniformly suspended, provide incredible heat transfer, and actually act to reduce galvanic corrosion.
The downside of Koolance LIQ-702 is the price. At over $30 for a 500mL bottle, it‘s one of the most expensive PC coolants on the market. I reserve it for the most extreme overclocked builds where every degree matters. But if you have the budget and want the best possible temps, you can‘t go wrong with LIQ-702.
Thermal Conductivity: 1.12 W/mK
Specific Heat Capacity: 3.1 kJ/kgK
Viscosity: 1.4 cP
Maintaining Your Coolant
To wrap things up, let‘s quickly go over some best practices for coolant use and maintenance:
- Always use distilled water if you‘re diluting a concentrate. Tap water can introduce contaminants.
- Flush your radiator before filling your loop, especially if it‘s new. Rads often contain manufacturing residue.
- Don‘t mix different coolant types or brands. Stick with one formula.
- Do a 24 hour leak test before powering on your system.
- Check your loop monthly for signs of biological growth, corrosion, or failing fluid dynamics.
- Plan to completely drain, flush and replace your coolant annually for best performance.
- Use either the CPU_FAN or CPU_OPT header to power your pump. Make sure it‘s running at full 12v.
And there you have it! You‘re now armed with the knowledge to choose the best coolant for your custom liquid-cooled PC. Whether you opt for a tried-and-true performer like EK-CryoFuel or Mayhems X1, a head-turning opaque like Thermaltake P1000 Pastel, or a blinged-out bottle of Vue, your system will thank you. Stay cool out there!
