Building a Loop from Parts: D5 vs DDC Pumps, Mounting and Control
Using a bare pump instead of a pump-reservoir combo gives far more freedom in placement, at the cost of deciding mounting and control yourself.
D5 vs DDC
In practice there are two pump families, both derived from German designs and built by several brands.
D5 moves more water, runs quietly, and generates little heat, but is large. DDC is compact with higher head pressure, suiting restrictive loops and multiple GPU blocks, but runs hotter and louder.
More blocks and radiators in series means more restriction. Restrictive loops favour DDC; simple loops favour D5.
| D5 | DDC | |
|---|---|---|
| 最大流量 | 多い（約1500L/h） | 少なめ（約1000L/h） |
| 最大揚程 | 低め（約3.9m） | 高い（約5.2m） |
| 発熱 | 小さい | 大きい（ヒートシンク推奨） |
| 音 | 低い唸り | 高めの音が出やすい |
| 大きさ | 大きい | 小さい |
| 向くループ | ラジエーター中心の素直な構成 | GPUブロックや細い流路が多い構成 |
Mounting and vibration
Most pump noise is vibration transmitted into the case, not the motor. Bolting directly to metal makes the whole case resonate.
Rubber bushings or a dedicated decoupling mount change this substantially.
Place the pump at the lowest point of the loop. A high pump ingests air and stops moving water. The reservoir goes immediately before the pump inlet.
Powering and controlling the pump
Pumps take power from SATA or a 4-pin peripheral connector, with the speed signal from a motherboard fan header. A fan header alone cannot supply the current.
Set that header to PWM. DC (voltage) control can prevent some pumps from starting or cause erratic behaviour.
Do not slow the pump too far. Reduced flow means reduced cooling. Run the pump at a fixed speed and control noise with the fans instead.
Always enable RPM monitoring. A stopped pump under load reaches dangerous temperatures quickly.
Loop order
Loop order has almost no effect on cooling: the water circulates and reaches a nearly uniform temperature.
What order affects is bleeding. Reservoir → pump → radiator → blocks → reservoir returns air to the reservoir most easily.
Routing for looks can kink tubing and reduce flow. Respect the minimum bend radius.
Frequently asked questions
What pump speed should I use?
Around 60–80% of maximum is enough flow for most loops. If you want it quieter, keep flow adequate and reduce fan speed instead.
What happens if the pump fails?
Flow stops and temperatures rise quickly. Set a minimum RPM shutdown in BIOS. Pumps are consumables, replaced every few years.