Koolance PMP-400 (Laing DDC 3.25)

Posted: February 26, 2011 in Pumps
Tags: , ,


This test is sponsored by Tim from Koolance, thanks!

This is one of the latest revisions of the popular Laing DDC series pumps, the Koolance PMP-400 (DDC3.25).  These have been one of the if not THE most popular pump in water cooling for several reasons:

  • Extremely small and compact size
  • Tuned for high pressure applications which is ideal for watercooling
  • Low noise
  • Aftermarket tops/easily modified for more performance

Sporting the factory top with 3/8" barbs


Two screw holes for solid mounting present. Torx screws hold factory top in place.
Top removed

Quality Ceramic Ball Bearing


For testing I performed my usual Pressure vs Flow rate full range testing.  Using this format allows you to estimate flow rates and see the entire operating range of the pump.

PQ testing Results

Using the 1GPM rule of thumb, you can see that the pump in stock trim is extremely capable.  An average restriction system would see around 1.1 to 1.2 GPM, a very high (5 block) system would see about .8GPM, and a low restriction system would see over 1.5GPM.  This is really a strong amount of pumping power.  The stock top also reaches nearly 14% efficiency which is good for small pump, and the average system will consume around 15 watts of power which is very respectable and something that would be easily powered my a fan controller if need be.  Looking at RPM, you can see by the red dotted line, that the pump has circuitry built in to reduce RPM as power consumption increases.  I’m not sure if this is current sensing or power consumption, but the RPM is reducing rather linearly from about 4700RPM at shutoff to 4100RPM at nearly max flow.  I suspect this is all in an effort to improve reliability.  The previous DDC3.2 models showed a touch more performance with low restriction systems and a touch less with very high restrictions, but for practical purposes about the same.  The bigger difference is the power consumption and heat generated.  The older DDC2 model could consume upwards 25 watts at free flow vs 16 watts of this newer model.


As a side experiment I tested two exact samples back to back to see what sort of sample variances are out there.  I found that there is some variance out there and this alone is part of the reason comparing across test beds is not such a good idea.   One tester could have sample A and another sample B, even if they had exactly calibrated test beds, they would end up with some differences.  As hobby testers we simply won’t have the luxury nor desire to test a large sample of products to average out sample variance.  Here are those results:

8% difference in flow rate and 18% in RPM



This newer revision is basically very similar to the older model with some minor emphasis for higher pressure and a fair improvement in reducing maximum power consumption levels.

Really the only downside to running this pump stock is the factory top which has a less than ideal efficiency elbow at the pump inlet and also which has fixed plastic 3/8″ barbs.   It’s still a very very capable pump in stock trim and for those looking for a really strong pump that are happy with 3/8″ ID tubing, this is one of the best pumps you can buy.


  • High pressure oriented is well tuned for water cooling
  • Very small 2.5″ x 2.5″ x 1.5″ footprint
  • Low power consumption
  • Low noise
  • RPM sensor wire


  • Base of pump gets hot to the touch
  • Factory top restricts tubing size to 3/8″

  1. Kyle says:

    How does this pump hold up against MCP35x?

    • Martinm210 says:

      It’s very close, but the 35X has a slight RPM advantage at higher speed. Besides that RPM controller difference the pumps motors are basically the same. Both are manufactured by Laing.

  2. michael says:

    hey Martin,
    i have a question and i can’t seem to find the answer anywhere. i have one of these pumps and it used to be connected to a koolance tms-200 board to control it. however the board fried but the pump is still working fine after just plugging it in to a (3pin to molex) molex again. those koolance tms boards sell for like 120 euro around here so my question was:
    i’ve seen a fan splitter with a 4 pin molex and then goes to 3 times 3 pin(fan) and one 3 pin to the motherboard, could i use this to undervolt/regulate my pump via the motherboard with out frying my motherboard?
    my thinking was that the power would come from the 4 pin molex anyway and the motherboard would not do much other that regulating what the output is on the other 3 cables just like it would with fans. i would leave the the other two leads empty. and this sells for roughtly 8 euro, so its alot cheaper.
    i was just wondering if iam on to something that could work and for far less money than a new koolance board.
    many thanks in advance!

    • Martinm210 says:

      No, The best thing to use is a Koolance SPD10. Unlike the MCP35x which only draws pwm signal for speed control, these 3pin DDC pumps can only be regulated by reducing voltage which IMO is too much of a load for a motherboard. It is possible some motherboard could take it but I have seen some fan controllers with heatsinks such as the sunbeam rheosmart fail trying to do so and would hate to see a MB fry.

      I would stick with a heavier duty method of regulating voltage. Some other fan controller might do ok also, but 20W is like regulating a dozen fans all on the same channel.