The first time you see a build with a chunky water cooler on the CPU, a glass side panel, and tubing snaking through the case, it’s hard not to want one. But before you spend hundreds on liquid cooling, it’s worth understanding what you’re actually buying. There’s a huge gap between the kind of cooling most people mean when they say “liquid cooling” and the wild custom loops you see on Reddit.

How liquid cooling works

Liquid is a much better thermal conductor than air. A water cooler uses a coolant to absorb heat from the CPU, carries it through a pipe or hose to a radiator far from the CPU, and then dissipates the heat into the air using fans. The CPU stays cooler because heat is being whisked away to a much larger surface area than any air cooler could provide.

The two flavors most builders care about are AIO coolers and custom loops.

AIO (All-In-One) coolers

An AIO is a sealed, factory-built liquid cooler. It has three parts:

  • A pump and water block that sits on the CPU.
  • Two flexible hoses.
  • A radiator with fans, mounted to the case.

You mount the radiator to the front or top of your case, screw the water block to your CPU, plug in the pump’s power cable, and you’re done. No refilling, no maintenance, no tubing bends to plan. They typically last 5-7 years before the coolant or pump degrades.

AIO radiators come in standard sizes:

  • 120mm: about as good as a decent mid-tower air cooler.
  • 240mm: a real step up. Handles mid-range and most enthusiast CPUs comfortably.
  • 280mm: similar performance to 360mm in less space.
  • 360mm: the sweet spot for high-end builds. Handles flagship CPUs at full load.
  • 420mm: overkill for almost everyone except hardcore overclockers.

Custom loops

A custom loop is a liquid cooling system you build yourself from individual parts: a pump, a reservoir, water blocks for each cooled component, rigid or soft tubing you cut and route, fittings to connect everything, and a coolant of your choice.

Advantages: best possible cooling, beautiful aesthetics, ability to cool both CPU and GPU in one loop, full customization.