How Quick Disconnect Couplings Are Used in Liquid Cooling Systems

Posted by
Cameron Wise on January 13, 2023

Electronic components are faster, denser, and run hotter than ever before, forcing cooling solutions to evolve alongside them. In the past decade, liquid cooling has become the standard for cooling high-performance computers and servers because of the excellent heat capacity of water. In fact, water’s heat capacity is 3500 times greater than the same volume of air. This efficient cooling prevents throttling due to high temperatures and leads to higher-performing components. While liquid cooling dissipates high temperatures far better than air, it provides unique safety challenges in a cooling system. Liquid cooling loops contain numerous connection points that must be sealed perfectly to eliminate the risk of water damaging components. Quick disconnect couplings provide a reliable seal, quality construction, and worry-free connectivity in a liquid cooling system.

What is a quick disconnect coupling?

A quick disconnect coupling is a fitting that provides easy installation and removal to and from a fluid or air line. While other fitting types require tools and manpower to connect and disconnect, quick disconnects can be attached to or detached from a system in a matter of seconds. Quick disconnect couplings made for liquid cooling systems feature non-spill features that may differ from those used in other applications. The seal type, pressure standards, and temperature limits of quick disconnect fittings differ between applications. As a result, fittings should only be used for the application for which they are designed. Liquid cooling quick disconnects are designed for low-pressure systems and typically have temperature limits of just above 100 degrees Celsius.

Learn more: What is a quick disconnect fitting and how does it work?

What makes quick disconnect couplings suitable for liquid cooling systems?

Quick disconnect couplings used for liquid cooling systems require special attention to detail in the manufacturing process. Any deviation in quality can cause drips that lead to server failure, data loss, and great expense. To ensure that a coupling is appropriate to use in a liquid cooling system, certain characteristics must be met. Couplings that safely and effectively move water throughout a system must possess the following attributes.


Because quick disconnect couplings for liquid cooling systems must be so precise, these systems should not utilize couplings that are not designed specifically for liquid cooling. One may think that couplings used in more rigorous systems, such as hydraulics and construction, are more durable and, as a result, better to use in a liquid cooling system. However, hydraulic couplings possess different standards for pressure and longevity, making them a risk factor in a liquid cooling loop. When incorporating couplings in a liquid cooling system, ensure they are appropriate for low-pressure applications.

Quick disconnect couplings are often the weakest link in the spill prevention of a liquid cooling system. This is due in part to the fact that other components of the system, such as the pumps, possess backup parts should the main component fail. Quick disconnect couplings, on the other hand, are a single point of failure without any form of backup. Consequently, should the coupling fail for any reason, the safety of the electronic components will be compromised. A single drop of water can cause an entire system to fail, so immaculate precision must be used in the development of liquid cooling couplings.

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Sturdy design

Quick disconnect couplings must be able to operate perfectly for long periods of time. When disconnected after months or years of operation, a coupling’s safety features must operate flawlessly, and the coupling itself must maintain the same performance upon reconnection. Changes in temperature and pressure should not manipulate the structure of the fitting material. Ensure that the maximum temperature and pressure of your system can be handled by the couplings you choose.

Quality seals

The quality of seals is inherently important in any coupling, but those used in liquid cooling systems are particularly vital. Not only do the coupling seals need to function perfectly, but they must also be compatible with the coolant used in the system. Incompatible coolant can cause ill effects such as seal swelling, shrinking, distortions, and hardening. Some couplings use dual seals to enhance the seal quality, but these can be less reliable than single seals because of greater friction.

Compatible materials

In a liquid cooling system, all materials used must be compatible with one another. Tubing, coolant, and couplings that are incompatible can cause corrosion, seal damage, and, ultimately, system failure. Metal couplings that contact a server’s frame can also cause corrosion if the metals are made of different materials. This contact can also start electrolysis, a process that causes a chemical reaction in the coolant.

Ease of use

Quick disconnect couplings are inherently easy to use. Both push-in and twist-in couplings are easy and simple to install, but some carry a spill risk. Couplings that use poppet valves for their anti-spill feature often trap some water inside the coupling itself. This can lead to a drop or two of water dripping onto the server unit. If the server is powered on, this can lead to failure of the whole connected system.

Quick disconnect couplings made by Colder Products Company (CPC) feature flush-face valves that prevent any risk of leaks upon disconnection. These dry-disconnect couplings shut off instantly, allowing at most a slight liquid coating on the valve itself. Couplings that are not designed specifically for liquid cooling likely do not feature the same level of non-spill protection. In applications where any amount of water can cause damage, ensure that the couplings used are designed for long-term use in that environment.

CPC couplings also feature color-coded bodies for cold (blue) and warm (red) water applications. This user-friendly detail gives a visual representation of cooling lines, allowing for easier maintenance.

To learn more about Colder (CPC) fittings, check out our buyer’s guide.

Compact design

In crowded server spaces, couplings must be as small as possible to strike a balance between water flow and saved space. If couplings are too large, they can take up room that could otherwise be used for additional server space. As a result, quick disconnect couplings with a compact design offer more value than those that take up additional room in an installation.

Metal vs plastic quick disconnect couplings for liquid cooling

Metal has long been the preferred material for fittings used in liquid lines because of its strength and longevity. The weight, conductivity, manufacturing cost, and corrosion susceptibility of metal have led to the development of plastic fittings for commercial cooling applications. The material polyphenylsulfone has recently been used in the development of quick disconnects because it offers high heat resistance and durability. While metal still holds some advantages for specific applications of quick disconnects, plastic fittings provide performance that surpasses that of metal fittings in some instances. When choosing the material for your cooling system, ensure that the coolant and tubing are compatible with the style of quick disconnect that you choose.

Advantages of plastic quick disconnects for liquid cooling

Plastic quick disconnect couplings provide the following advantages over metal quick disconnects:

  • Low electric conductivity. All-metal quick disconnects conduct electricity. This is not an issue in normal applications, but it can cause electrolysis should the coupling contact the server frame.
  • Less spill risk. Over time, the protective coating on metal couplings can wear away, exposing bare metal to the fluid in the system. This leads to corrosion that compromises the integrity of the coupling.
  • Less expensive. Plastic is inherently a lower-cost material than metal, so plastic fittings are less expensive than their metal counterparts.
  • No corrosion risk. All metal contains some corrosion and oxidation risk, while plastic fittings possess neither.
  • Plastic fittings are typically less than one-quarter of the weight of metal fittings. This makes for a system that is easier to install and maintain.

Advantages of metal quick disconnects for liquid cooling

  • More durable. While metal is susceptible to corrosion and oxidation damage, they are more durable in extremely rough applications. While most liquid cooling systems do not need to take advantage of this increased durability, it is an advantage to consider.
  • Handle higher pressure and temperatures. Metal quick disconnects can handle far higher pressure and temperatures than plastic fittings. However, in the example of liquid cooling systems, the temperatures and pressure reached should not pose a threat to plastic fittings.

Ultimately, both metal and plastic quick disconnect couplings provide long-lasting, reliable connections in liquid cooling systems. In low-pressure, low-temperature applications, plastic fittings are a more economical, practical solution. For water lines with high pressure and temperatures, metal fittings are the optimal solution.

Learn more about liquid cooling systems: Using distilled water for liquid cooling a PC | How to choose the right liquid cooler fitting for your system



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