Custom Loop Water Cooling: Parts, Cost, and Failure Modes
A custom loop is not only about temperature. It is about noise and appearance too. Decide whether the cost and upkeep are worth it first.
How it differs from an AIO
An AIO is a sealed, finished unit. A custom loop is assembled from parts and filled by hand.
Cooling capacity is mostly radiator area. At equal area an AIO is close. A custom loop wins by cooling the GPU in the same loop and by fitting larger radiators.
Noise is where custom loops clearly win, because large radiators can run at low fan speeds.
| Part | Role | What to watch |
|---|---|---|
| CPUウォーターブロック | CPUの熱を水へ移す | ソケット対応を確認する |
| GPUウォーターブロック | GPUの熱を水へ移す | 基板の型ごとに専用。同じ型番でも基板違いは付かない |
| ラジエーター | 水の熱を空気へ逃がす | 厚みとファンの相性。ケースの対応寸法 |
| ポンプ | 水を回す | リザーバー一体型が扱いやすい |
| リザーバー | 空気抜きと補充 | 無いと空気が抜けきらない |
| フィッティングとチューブ | つなぐ | 内径・外径をチューブと合わせる |
| 冷却液 | 熱を運ぶ | 防腐剤入り。色付きは詰まりやすい |
Preventing leaks
Most leaks come from under-tightened fittings or tubing pulled out of a too-tight bend, not from part failure.
Always leak-test with only the pump powered, for several hours, before applying power to anything else.
New radiators often contain metal debris. Flush them before assembly or the pump will suffer.
Cost and upkeep
A CPU-only loop runs roughly ¥50,000–80,000 in parts; adding the GPU brings it to ¥100,000–150,000 (2026, Japan). Case and fans are extra.
Coolant is replaced every one to two years. Neglect leads to growth and corrosion, then blockages.
If you are away from the machine for long periods, consider that a leak may go unnoticed.
Frequently asked questions
How much cooler is a custom loop?
It depends on radiator area. A 360mm loop is often around 10°C below a large air cooler on the CPU, but close to an AIO of the same size. The real gains are cooling the GPU in the same loop, and noise.
Will a leak destroy my parts?
If it leaks while powered, yes. That is why a pump-only leak test of several hours before first boot is not optional.