What is Liquid CPU Cooling?

[Hardware Explained]

The computers I work on every day are cooled by an on-board water cooled heat exchanger—without water cooling (WC), they’d either run slowly (best case) or overheat and shut down (worst case.) Outside the enterprise, liquid cooling isn’t as necessary but, for around $100 US, you too can enjoy liquid cooling technology on your overclocked home rig. In this guide, we’ll cover the basics on liquid cooling  and explain why liquid cooling is superior to air cooling. We’ll then look into why you really don’t need liquid cooling for your home PC—but don’t let that stop you!

Liquid and Electronics? What Kind of Liquid?

Generally, a water-based solution is used due to it’s high thermal conductivity. Yes, water is ionized and electronically conductive so your best protection against accidents is good planning for and careful testing of your liquid cooling system.

Distilled water is a good choice if your CPU block doesn’t come with a solution. I recommend using a liquid-cooling specific solution because you really don’t need very much and these solutions are formulated to inhibit microbial growth in your system.

This guide will refer to “water” throughout but you can use any liquid like alcohol, oil, glycol etc. As your system is sealed tightly, a water-based solution is always the best option because of its excellent thermal conductivity (23 times more so than air) relative to other liquids—bettered only by mercury, which isreally not a good liquid to use!

What is Liquid Cooling?

Because water is an excellent thermal conductor, it’s ideal for dissipating heat from a CPU. Liquid cooling is the process of exchanging heat from a hot processor into water and circulating the heated water to a radiator (where the heat is exchanged from the water to the outside air.) The liquid cooling mechanism forms a circuit (more about that coming up) so the liquid is constantly drawing heat from the CPU—keeping your PC’s internals nearly as cool as the ambient temperature in your room.

Note: You can also cool other hardware like the Graphics Processing Units (GPUs), hard drives, the northbridge (NB)*, and the southbridge*.

*If your CPU setup utilizes them (Sandy Bridge processors, for example, integrate the CPU with the northbridge.)

What Components Make up a Liquid Cooling System?

A liquid cooling system is composed of five essential components:

1. CPU Water block: in direct contact with your CPU a thin piece of (usually) copper sits between the cool water and your hot CPU
2. Water pump: Keeps the water flowing around the system/circuit
3. Radiator: Radiates heat from the water outside your PC case. Usually assisted by a fan to be effective
4. Tubing: Keeps the (conductive) water from spilling on your shiny, expensive equipment
5. Fillport/reservoir: Not shown in the diagram below (many radiators come with one.) This is how you get water into the system

Optionally, you can install a liquid level and flow indicator to ensure enough water is in your system and that it’s actually flowing. It’s not necessary, but they do look pretty cool if placed visibly in your PC tower. Here’s a diagram showing the flow between the components. The arrows represent tubing; blue for cool water; red for warmed water:

The CPU water block is so effective because the water is drawn back and forth in a “maze” like pattern before leaving the CPU block and heading to the radiator. This helps the water pick up the most heat from the CPU before it’s cooled and circulated back to the CPU.

How Do I Make a Good Liquid Cooling System?

Just like any other PC hardware, you get what you pay for. Go too fancy and you experience the law of diminishing returns. I have a couple of recommendations if you’re looking to purchase a liquid cooling system:

• Unless you think you’ll really need it, use 1/4 -3/8 inch ID (inner diameter) tubing. 1/2 inch requires a bigger pump and is more difficult to integrate into tighter spaces so look for equipment that has 3/8 inch or smaller connectors.
• Don’t under-estimate the need for good tubing: PVC will kink easily and is prone to deterioration over time. There are some good options for tubing—Tygon is highly recommended.
• Ensure your pump can move at least 80 gal/hr. Unless you’re cooling many components, anything over 300 gal/hr is just overkill. Furthermore, a high volume pump will push the water too quickly and wont adequately pick up heat in the process. At worst, a high powered pump may lead to leaks and will usually be louder.

If you’re serious about buying a liquid cooling system, you probably know more than I can articulate in this guide. If you’re really stuck, we can help you over at Windows Forums. FrozenCPU and Danger Garden are suppliers of kits and components and are a good resources for equipment.

Is Liquid Cooling Really Worth it?

No consumer-grade CPU, sold today, requires liquid cooling to operate out of the box. However, there are a few reasons you might want to use liquid cooling:

1. To cool your overclocked CPU
2. To reduce/eliminate audible fan noise
3. Because, no matter how long we’ve been using this technology, it’s still pretty cool and is worth major geek points

Even with a heavily overclocked CPU, you can keep heat under control using proper forced ventilation (fans); however, if you’re really pushing your hardware (perhaps you like to watch FurMark), liquid cooling will help your CPU perform optimally.

You will probably never really benefit from liquid cooling but don’t let me stop you investing in some sweet equipment if that’s what you want to do. Have fun and test your setup for a few hours (or days) before placing it in your PC to ensure not even the tiniest leak forms.

Update: Tips on Water Cooling

• Be careful when threading your tubes. If you cross-thread and don’t test your system extensively, you might find a slow leak forms over time. Enough of a leak to do irreversible damage.
• Research hardware that overclocks well. Find a forum where people have taken the time to find the best OC processors for your budget.
• Some cases are good for water-cooled setups and some are not. See what others are using and base your purchasing decisions off them
• WC becomes more useful when you OC your CPU and GPU/2x GPUs. If you want to cool more than your CPU (why not?) go in this order:
• Northbridge (if your CPU doesn’t have it integrated)
• GPU
• HDD
• SSD
• Reservoirs provide increased volume for liquid; thereby increasing thermal capacity. For this reason, they’re a better option than a  fillport
• i7′s run very hot when overclocked. Use a 220 – 320 size radiator (RAD)
• Test your system for 3-48 hours before putting it in your case. Place it on a grey t-shirt or paper so you can easily spot leaks
• If you get a leak during testing, reconfigure your setup and change the t-shirt/paper so you’re absolutely sure there’s not a single leak
• If you get water on your motherboard (MB):
• Not much water: hang it and put a slow blowing fan on it for 24 hours/air compress it dry. Leave the board for another 24 hours and then attempt to power on. Increase the drying time to three days in climates with RH >50%
• A lot of water: rinse it with distilled water, hang it and put a slow blowing fan on it for 48 hours/air compress it dry. Leave the board for another 24 hours and then attempt to power on. Increase the drying time to five days in climates with RH >50%
• Setting up a successful water cooling system is fairly easy but don’t rush the process (see next point)
• Take your time if you’re a first-time buyer. It’s unlikely you know exactly what you want right now. Do some reading and take your time on this project