What Is a Liquid CPU Cooler? Explanation of How It Works, Types, and Differences from Air Coolers

To maximize the performance of a computer, cooling the CPU is essential.

Especially with high-performance CPUs or in overclocking environments, insufficient cooling can lead to reduced performance or even hardware failure.

One cooling solution that is gaining attention is the “liquid CPU cooler.”

Compared to air cooling, liquid coolers offer higher cooling performance and quieter operation, making them highly effective in high-end PC environments.

This article explains in simple terms the mechanism, advantages and disadvantages, types, and how to choose a liquid CPU cooler.

Use this as a reference to select the best CPU cooler for your PC setup.

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What is a Liquid CPU Cooler?

This section explains the features of liquid CPU coolers, how they differ from air coolers, and which CPUs they are best suited for.

What is a Liquid CPU Cooler?

A liquid CPU cooler is a cooling device that transfers the heat generated by the CPU to a coolant, then releases that heat outside the case through a radiator and fan.

While air coolers “cool directly with air,” liquid coolers “transfer heat using a liquid.”

There are two main types of liquid coolers: “AIO (All-in-One)” and “custom loop.”

AIO liquid coolers are products where the pump, water block, tubes, radiator, and fan are integrated and designed to require no maintenance.

Liquid CPU coolers generally offer higher cooling performance than air coolers, and because fan speeds can be kept lower, they also tend to be quieter.

Additionally, the structure using a pump, tubes, and radiator allows for a cleaner and more stylish look inside the case.

On the other hand, liquid coolers are usually more expensive than air coolers, and installation can be a bit more complex due to the need to mount the pump and radiator.

Currently, the most common liquid coolers used in custom-built and BTO (Build-To-Order) PCs are of this type.

Custom loop liquid coolers are built by individually selecting and combining a pump, reservoir, radiator, water block, and tubes.

The biggest advantage is the potential for extremely high cooling performance, depending on the parts used.

Custom loops also offer a high degree of customization, allowing for beautiful aesthetics with LED lighting and unique tubing layouts.

However, they are more expensive and require advanced knowledge and experience to build and maintain.

There is also a higher risk of leaks depending on the parts and handling of the coolant, so this type is not recommended for beginners.

Although I have never built a custom loop myself, from watching videos, the difficulty of installation seems to be about 1 for air coolers, 1.5–2 for AIO liquid coolers, and 100 for custom loops.

Basic Structure and Cooling Mechanism of Liquid CPU Coolers

A liquid CPU cooler is mainly made up of the following parts:

• Water Block
  The part that makes direct contact with the CPU, efficiently transferring heat from the CPU to the coolant. The base is usually made of copper or nickel-plated copper, and thermal grease (CPU grease) is used to absorb heat from the CPU surface.
• Pump
  Circulates the coolant, carrying the heat absorbed at the water block to the radiator. In AIO coolers, the pump is often integrated with the water block.
• Radiator and Cooling Fan
  These parts cool the warm coolant sent by the pump. The radiator has many fins, and the fan blows air through them to efficiently dissipate heat outside. Sizes range from 120mm to 360mm or more, directly affecting cooling performance.
• Tubes
  Connect the water block and radiator, providing a path for the coolant to circulate. Made of flexible material for easy routing inside the case.

The cooling process works as follows:

• Heat Absorption from the CPU
  The heat generated by the CPU is transferred to the base plate of the water block and efficiently moved to the coolant via thermal grease.
• Heat Transfer by Coolant
  The pump circulates the coolant, carrying the heat from the CPU through the tubes to the radiator.
• Heat Dissipation at the Radiator and Cooling by Air
  The heat spreads through the fins inside the radiator, and the attached fan blows air to efficiently expel the heat outside.

With this structure and mechanism, the CPU temperature can be lowered, maintaining stable operation.

Liquid Coolers Are a Good Choice for High-End CPUs

High-end CPUs like Intel Core i7/i9 or Ryzen 7/9 consume more power and generate more heat, so it is important to ensure sufficient cooling performance.

Large air CPU coolers can usually keep CPU temperatures and noise levels under control in most situations.

For example, in a desktop PC with an Intel Core i7-14700F and RTX 4060 Ti using a large air cooler, running a heavy 3D game like FF15 at maximum settings resulted in about 30% CPU usage and a CPU temperature of around 60°C, showing that cooling was sufficient.

However, for long periods of heavy workloads, or when CPU usage stays at 80–100%, or when overclocking, a liquid CPU cooler becomes a viable option.

Liquid coolers have high cooling efficiency and can keep temperatures stably low, helping to prevent thermal throttling and allowing for quieter operation.

In summary, for normal gaming, a large air cooler is enough, but for those who want extra cooling headroom or use their PC for heavy workloads or overclocking, a liquid CPU cooler is a better choice.

Overkill for Low-End and Mid-Range CPUs

Using a liquid CPU cooler with a low-end or mid-range CPU often results in more cooling performance than the CPU actually needs, making it excessive. (About low-end and mid-range CPU classifications)

These CPUs do not generate much heat, and the included stock cooler or a regular air cooler is usually sufficient.

Therefore, using a liquid cooler may only slightly lower CPU temperatures or reduce noise, and considering the cost, it is often overkill for these CPUs.

For low-end or mid-range CPUs, a large aftermarket air cooler provides enough cooling, so if cost performance is important, a liquid cooler may be too much.

Types of Liquid CPU Coolers

There are two main types of liquid CPU coolers: “AIO (All-in-One)” and “custom loop.”

Here is a table summarizing their features and differences:

	AIO Liquid Cooler	Custom Loop Liquid Cooler
Image
Features	・Mainly All-in-One (AIO) type ・Factory-assembled products ・No assembly required, ready to use ・Almost maintenance-free ・Simple design	・Choose and assemble parts individually ・Customizable for each part ・Requires assembly and maintenance
Size	・120 / 240 / 360mm, etc. Radiator size selectable ・Fits most cases	・Radiator, reservoir, etc. freely selectable ・Can be made very large
Cooling Efficiency	・Better than air cooling, but often less than custom loop	・Very high cooling performance ・Can cool multiple parts at once
Quietness	・Some fan and pump noise, but many quiet models	・Can be very quiet depending on design ・Large radiators allow low fan speeds
Price Range	・Relatively affordable, from around 10,000 yen ・Good cost performance	・Often expensive, several tens of thousands of yen ・Costs for each part
Ease of Installation	・Easy to install, even for beginners ・Comprehensive manuals	・Requires knowledge and skill ・Assembly and maintenance are time-consuming

AIO Liquid CPU Coolers

AIO (All-in-One) liquid CPU coolers are factory-assembled liquid coolers sold as complete products with the pump, water block, radiator, tubes, and fans already integrated.

Users do not need to assemble anything; they can be installed just like air coolers.

Radiator sizes are mainly divided into 120mm and 140mm types.

120mm types come in three sizes:

• 120mm (1x 120mm fan)
• 240mm (2x 120mm fans)
• 360mm (3x 120mm fans)

140mm types come in three sizes:

• 140mm (1x 140mm fan)
• 280mm (2x 140mm fans)
• 420mm (3x 140mm fans)

There are many variations, so you can choose based on cooling performance and case compatibility.

AIO liquid coolers offer better cooling than air coolers and keep CPU temperatures stable, making them suitable for long periods of heavy workloads or overclocking.

Prices start from around 10,000–20,000 yen, which is more expensive than air coolers but cheaper than custom loops.

Since they are sealed by the manufacturer, maintenance is almost unnecessary, and even beginners can install them easily, making AIO liquid coolers very popular.

Custom Loop Liquid CPU Coolers

Custom loop liquid CPU coolers are cooling systems built by individually selecting and combining parts such as the water block, radiator, reservoir (tank), pump, tubes, and coolant.

Unlike AIOs, which are sold as complete products, custom loops offer very high customizability and expandability.

Cooling performance is extremely high, and adding more or larger radiators can greatly increase heat dissipation.

Also, not only the CPU but also the GPU, memory, and motherboard VRMs can be cooled in the same loop, which is a major advantage.

This allows for cooling the entire system, not just the CPU.

In terms of quietness, using larger radiators and lowering fan speeds can create a very quiet cooling environment.

Additionally, combining different tube materials, coolant colors, and LED lighting allows for beautiful custom aesthetics, which is a popular reason for choosing custom loops.

On the other hand, costs can easily exceed several tens of thousands of yen, with expenses for each part.

Installation and maintenance also require considerable knowledge and experience, making it a high hurdle for beginners.

Therefore, custom loops are best suited for advanced users or enthusiasts who want “overwhelming cooling performance,” “freedom of customization,” and “beautiful aesthetics.”

How to Choose a Liquid CPU Cooler

This section explains the key points to consider when choosing a liquid CPU cooler.

The main focus is on cooling performance and compatibility with other parts.

Check Cooling Performance (TDP Support)

To choose the right CPU cooler, it is important to select a cooler with cooling capacity that matches the CPU’s TDP (Thermal Design Power).

TDP indicates the maximum amount of heat the CPU is expected to generate, so the cooler should have at least this much cooling capacity.

Also, check if your PC case supports liquid CPU coolers, the supported sizes, airflow, budget, and noise level to find the best fit for your needs.

If you are not sure where to find the TDP, let’s look at it together.

First, check the specifications on the CPU’s product page for TDP.

CPU: Intel Core i5 14400F Example

In the specifications, refer to the “Maximum Turbo Power” (the highest wattage value).

For the Intel Core i5 14400F, this is 148W.

CPU: AMD Ryzen 5 7600 Example

In the specifications, refer to the “Default TDP/TDP” value.

For the AMD Ryzen 5 7600, this is 65W.

CPUs have a “turbo mode” feature that temporarily increases clock speed above the base value for extra performance.

For Intel, this is called Turbo Boost Technology; for AMD, it’s Precision Boost. With these features, the CPU can exceed the listed TDP.

Also, overclocking can push the CPU beyond its rated TDP.

Therefore, use the CPU’s TDP as a reference, and choose a CPU cooler with some extra headroom.

The TDP supported by a CPU cooler is sometimes listed on the official product page or distributor’s site, but not always.

Check the TDP of both the CPU and cooler, and choose a cooler with a little extra capacity.

That said, sometimes TDP is not listed for CPU coolers, and turbo mode or overclocking can push the CPU beyond its rated TDP, making it hard to judge.

In such cases, just remember these two points:

• For mid-range CPUs, use a “medium or large air cooler”
• For high-end CPUs, use a “large air cooler” or “AIO liquid cooler with at least two fans”

Cooling performance varies by product, but this is a good general guideline.

Check CPU Cooler Socket Compatibility with the Motherboard

When choosing a CPU cooler, make sure it matches the socket type of your motherboard.

The socket is the connector on the motherboard where the CPU is installed. The CPU and motherboard must have matching sockets, and the CPU cooler must also be compatible.

CPUs and motherboards usually support only one socket type, but many CPU coolers support multiple socket types.

For example, a motherboard may support only LGA1700, but a CPU cooler may support Intel LGA1700, LGA1200, LGA1151, LGA1150, LGA1155, LGA1156, and AMD AM5, AM4, etc.

So, as long as the CPU cooler supports the socket type of your motherboard, it’s compatible.

Because of this, socket compatibility rarely limits your choice of CPU coolers, so you can choose based on performance, design, and other preferences.

When assembling, use the included mounting hardware for your socket type to attach the cooler to the motherboard.

≫ Related article: About CPU Cooler Socket Types [Custom PC]

Check Radiator Size and PC Case Compatibility

When choosing an AIO liquid CPU cooler, make sure the radiator size fits your PC case.

The radiator releases heat from the CPU to the outside via the coolant, and larger radiators can dissipate more heat efficiently.

Radiator sizes are mainly divided into 120mm and 140mm types.

120mm types come in three sizes:

• 120mm (1x 120mm fan)
• 240mm (2x 120mm fans)
• 360mm (3x 120mm fans)

140mm types come in three sizes:

• 140mm (1x 140mm fan)
• 280mm (2x 140mm fans)
• 420mm (3x 140mm fans)

Check the size of the liquid CPU cooler you want and look at your PC case’s specifications to see where and what size radiator can be installed.

PC cases vary, but many support installation at the front, top, rear, side, or bottom. Many cases support both 120mm and 140mm types, allowing for flexible installation.

Design and LED Lighting

The design and presence of LED lighting on a CPU cooler can greatly affect the look and feel of your PC.

Recently, more models come with colorful LED or RGB lighting, making it easy to create a vibrant look inside the case.

If your case has a transparent side panel, choosing a cooler with LED lighting can dramatically change the overall impression of your PC.

On the other hand, simple designs or models without lighting remain popular, especially for those who prefer a calm look or prioritize quietness.

Choose the design and LED features that match your preferences, PC usage, and environment.

Differences Between Liquid and Air CPU Coolers

There are both liquid and air CPU coolers, and this section explains their differences, advantages, and disadvantages.

Note: This section assumes AIO liquid coolers.

Comparison of Liquid and Air CPU Coolers

Liquid coolers transfer heat from the CPU to the coolant using a water block (pump), then move the liquid through tubes to the radiator, where fans release the heat to the outside air.

In contrast, air coolers use a heatsink and fan to directly transfer heat from the CPU to the air—a simpler structure.

In short, liquid coolers use liquid to move heat, while air coolers use metal and air directly.

Here is a summary of the differences by category:

These are general trends by cooling method; actual performance varies by product. Basically, liquid CPU coolers offer higher cooling performance than air coolers.

Based on cooling specs and experience from reviewing computers, large air coolers can handle high-end CPUs in terms of temperature and noise.

However, for overclocking or long periods of heavy use with high-end CPUs, liquid CPU coolers offer more headroom.

Large air coolers are generally quiet, but for even quieter operation, liquid coolers with two or three fans (which can run at lower speeds) are recommended.

Advantages of Liquid CPU Coolers

Here are the advantages of liquid CPU coolers compared to air coolers:

• High cooling performance for high-end CPUs and overclocking
  Liquid CPU coolers use coolant and radiators to efficiently dissipate heat, offering better cooling than air coolers. They keep CPU temperatures stable even during long periods of heavy workloads or overclocking, improving system stability and safety.
• High quietness
  Liquid coolers can efficiently remove heat, allowing for lower fan speeds and quieter operation. Multiple fans (dual or triple) can further reduce noise by distributing the load. However, some people may notice pump noise.
• Less obstruction to case airflow
  Radiators and fans can be installed at the edges of the case (mainly front or top), freeing up space inside and improving airflow. This can also slightly improve cooling for memory and motherboard components.
• Stylish appearance and high customizability
  The design of pumps and tubes is simple, and internal wiring is tidy. Many models offer customizable LED lighting and coolant colors, allowing for unique gaming or custom PC builds. This is a big draw for users who value appearance and customization.

Basically, liquid CPU coolers offer higher cooling performance, but large high-end air coolers can also provide sufficient cooling, so liquid is not always “absolutely better.”

For long periods of heavy workloads, liquid coolers are recommended, but for heavy 3D gaming, a large air cooler is usually enough.

For example, in a desktop PC with an Intel Core i7-14700F and RTX 4060 Ti using a large air cooler, running a heavy 3D game like FF15 at maximum settings resulted in about 30% CPU usage and a CPU temperature of around 60°C, showing that cooling was sufficient.

In other words, for 3D gaming, a large air cooler is enough. Only when doing tasks like data analysis or programming that use all CPU cores (with CPU usage at 80–100%) should you consider a liquid cooler.

Air coolers can still handle these loads, but liquid coolers become an option when you want even more headroom.

Disadvantages of Liquid CPU Coolers

Here are the disadvantages of liquid CPU coolers compared to air coolers:

• Higher price
  Liquid coolers are more expensive than air coolers, usually costing over 10,000 yen, with high-end models exceeding 20,000 yen. They have more parts, so manufacturing costs are higher. If cost performance is important, air coolers may be better.
• Installation is a bit more complex
  In addition to the water block on the CPU, you need to install the radiator and fans on the case, making the process more involved than with air coolers. Tube routing and adjusting the orientation of logos on the water block can also add complexity.
• Risk of leaks
  Because liquid coolers circulate coolant, there is a structural risk of leaks from tubes or connections. However, modern AIOs are sealed and maintenance-free, so actual leaks are very rare. Most leaks are due to initial defects or aging after long-term use, and the risk is low but not zero.

Air coolers can be purchased for a few thousand yen, but liquid coolers have more parts (pump, radiator, tubes, etc.), making them more expensive.

As for leaks, I have never heard of an AIO leaking, so it is a very rare event. However, if a leak does occur, it can damage other PC parts, leading to greater losses.

Therefore, choose products from reliable manufacturers, use them within the warranty period, and check them regularly.

Frequently Asked Questions About Liquid CPU Coolers

This section answers common questions about choosing and using liquid CPU coolers.

How often should I clean my CPU cooler?

Dust tends to accumulate on the fan, so clean it about once every six months to a year.

For cleaning methods, see the related article below.

≫ Related article: How to Clean a Custom PC and Required Tools [With Photos]

The article uses air coolers as an example, but the fan cleaning process is the same for liquid coolers.

How should I apply thermal grease, and which type should I choose?

Thermal grease should be applied as evenly and thinly as possible between the CPU and cooler. However, most CPU coolers come with pre-applied grease, so you can install them as is.

If you remove the cooler during installation or need to reapply grease after a few years, you will need to choose and apply thermal grease yourself.

If you want to use a different type of grease or apply it differently, see the related article below for details on types and application methods.

≫ Related article: Role, Types, Application, and Lifespan of CPU Grease [Custom PC]

Can I replace just the fan on a CPU cooler?

The fans on liquid CPU coolers can usually be replaced with standard PC fans.

Most liquid coolers use standard 120mm or 140mm fans on the radiator, so you can swap them for your preferred fans.

However, check the thickness and connector type (3-pin/4-pin) before replacing. If the combined thickness of the radiator and fan is already close to interfering with other parts, replacing the fan with a thicker one may cause interference.

≫ Related article: How to Choose PC Case Fans for Custom PCs [Performance / Features / Compatibility]

Where can I check the fan speed, airflow, and noise level of a CPU cooler?

To check the fan speed, airflow, and noise level, look at the product specifications for “RPM” (revolutions per minute), “CFM” (cubic feet per minute), and “dBA” (decibels).

RPM shows how many times the fan spins per minute. Higher RPM usually means better cooling, but also more noise.

Noise level (dBA) indicates how loud the fan is. Lower numbers mean quieter operation. Around 30 dBA is considered quiet.

Can liquid CPU coolers leak? What are the countermeasures?

AIO liquid CPU coolers are sealed and maintenance-free, so there is no need to refill or replace coolant, and the risk of leaks is very low.

However, the risk is not zero, so caution is needed. If a leak occurs, it can damage internal PC parts, so be careful.

Main causes include rare initial defects, aging of hoses or connections after long-term use, or improper installation.

In actual user reports, leaks are very rare even after years of use.

Countermeasures include:

• Regularly check hoses and connections for bulges, cracks, or condensation
• Read the manual carefully and secure all screws and fittings during installation
• Choose products from reliable manufacturers and use warranty support if needed

Is it okay for beginners to try custom loop liquid cooling?

Custom loop liquid cooling is not recommended for beginners.

At least build a few PCs and get used to the basics before trying it.

This is because custom loops require specialized knowledge and effort for part selection, assembly, and regular maintenance.

For first-time builders, there is already a lot to learn about other parts and assembly, so adding custom liquid cooling makes it much harder.

If you really want to try it, do so after building several PCs.

Summary: Liquid CPU Coolers Are Recommended for High-End CPUs and Those Who Want Extra Cooling Performance!

This article explained the mechanism, features, differences from air coolers, advantages and disadvantages, and how to choose a liquid CPU cooler.

Here are the key points again:

Liquid CPU coolers provide high cooling performance and quiet operation, especially excelling with high-end CPUs and in overclocking environments.

However, for simply using a high-end CPU, a large air cooler is often sufficient.

On the other hand, for long periods of heavy workloads or environments where CPU usage remains high, liquid CPU coolers can keep temperatures more stable and lower.

In summary, if you prioritize cost and ease of installation, a large air cooler is a good choice. If you want extra cooling headroom, a liquid CPU cooler is the best option.

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