There is quite a number of pump types on the market, but the majority of users are choosing between the two most popular pumps: the D5 and the DDC. Both the D5 and DDC pumps have quite an old base design and none of the two has gone through some major changes. It’s like “you cannot reinvent the wheel”. The only big change that was over the years is that both the D5 and DDC pumps got PWM support. It means they are now featured with a sophisticated way of controlling their speed. If you are fresh to the subject and want to know more about PWM, just take a peek at my “What is PWM and how does it work?” blog article.

Although the D5 and DDC labels define the base design of the pump, there are a lot of versions available. There are some fakes on the market, some companies make slight changes to the pump design, while others just slam their own brand label on it. Now, let’s start with the basics and the key differences between these two pump types.

On the left-hand side is a DDC PWM pump with a Plexi top,
on the right-hand side is an D5 PWM Motor alone.

The D5 is more massive, it takes up twice as more space than the DDC. An average D5 pump offers a theoretical flow rate of 1500 liters per hour with a head pressure of 4m. Head pressure in pumps is determined with a simple test – hanging a hose vertically and measuring to what height the liquid can be pumped.

The D5 spherical motor pump.

The key design of the D5 spherical motor pump is its simplicity. The only moving part in a spherical motor is a hemispherical impeller unit (rotor), which sits on an ultra-hard and wear-resistant ceramic bearing ball. The rotor itself contains a permanent magnet which is driven by the electromagnet coils placed under the metal shell. It’s a simple force interaction between the permanent magnet (rotor) and the electromagnet (stator).

The D5 spherical motor pump with its hemispherical impeller removed.

The magnetic rotor always balances itself ideally on the ceramic bearing. The pump is very robust and the parts exposed to the fluid are corrosion resistant, which provides an exceptionally long service time.

The DDC pump is probably the world’s first pump to be used in mass-produced liquid cooled workstations. Due to its small size and great output, the DDC pump easily found its way to the hands of liquid cooling enthusiasts. The average DDC pumps that have a flow rate of 1000 liters per hour with a head pressure of 5 to 7m.

The DDC spherical motor pump.

DDC pump works on the same simple spherical motor principle as D5 unit. The only moving part is a spherical shaped permanent magnet impeller rotor, which is seated on a wear-resistant ceramic ball. The spherical ceramic bearing ball and the overall design removes the occurrence of bearing play (also applies to the D5 design). Since the rotor of a DDC pump is also magnetically held in the designated position, small particles of dirt and maintenance do not present a problem.

The DDC spherical motor pump with its impeller removed.

Both pumps, the D5 and the DDC are water lubricated. In other words, they use wet rotor design. Therefore, it is strongly recommended not to run any of these pumps dry. Also, both types of pumps should have liquid circulating through them with a temperature lower than 60°C.

The D5 and DDC pumps with corresponding pump top parts.

Both types of pumps have a wide range of accessories, the so-called “pump top”. Custom D5 pump tops and DDC pump tops are usually made of acetal or plexiglass (acrylic). These parts bring additional flexibility and aesthetics to the pump itself, but can also positively impact performance.

A D5 and DDC pump mounted with pump tops.

These pump add-ons have female G1/4” threads, which means you can choose any fitting you like. It is crucial to point out that both D5 and DDC pump and pump tops have predefined inlet and outlet ports which have to be respected in order for your liquid cooling loop to work properly.

Examples of pump and reservoir combo units, and dual pump mounts.

The list of combinations and additional parts is quite a subject on its own. There are various reservoir combo options for these pumps. Having two pumps in one cooling loop can boost flow rates and performance, and lower operating noise. The other reason why some refer to using dual pumps is safety because a backup pump is always welcome. Pumps rarely malfunction, especially the D5 model, but not everyone is using liquid cooling for a part time gaming rig. When it comes to serious workstations or servers, having an extra pump is never a bad idea.

A 120mm fan along the D5 and DDC pump for size comparison.


  • The D5 can offer bigger flow rates at a lower pressure,
  • while the DDC has higher pressure but lower flow rates.
  • Also, it’s important to know that small DDC pumps can be a bit noisier than the D5 models
  • The DDC, being more compact, can also run a bit hot, and that’s why additional pump heatsinks are available on the market.
    These heatsinks are not necessary, but it is something that could reduce wear and prolong the life of the pump.

If you are building a complicated loop with many angled adapters and several water blocks, a pump with high pressure (DDC) will have the advantage.
If you are building a small form factor PC with limited space, again, the DDC would be the smarter choice.
The absolute all-rounder might be the PWM versioned D5. It has high flow rates and it runs cool and silent.
In most cases, one D5 can run for several years without breaking a sweat.

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