Koolance RP-402X2 & RP-452X2

Posted: February 25, 2011 in Pumps
Tags: , , , , ,

Welcome to my living review of the Koolance RP-402X2 and RP-452X2 drive bay reservoir systems. First, I would like to give a huge thanks to Tim from Koolance for sponsoring. The RP-402X2 and the RP-452X2 are the latest in the dual bay pumping reservoir craze.

Koolance RP-402X2 & RP-452X2

These are exceptionally well made “Acetal” reservoirs that can hold and run two (PMP-400,  or PMP-450) pumps all in a single dual bay reservoir. These also have two independent reservoirs that can be run independently, shared, or in series depending on your desired setup needs.

RP-402X2 is designed for the PMP-400 pumps (should also work with most DDC/MCP35 series)
RP-452X2 is designed for the PMP-450 pumps (should also work with D5/MCP655 series)

Both reservoirs share the same reservoir system with only slight modifications made to accept each type of pump. I’ll spend some time going though various tests and review items below.

General Information

Testing in progress

Testing Toys!!..
For performance testing I am employing my usual pump testing tools. Flow rate is measured using a King Instruments 7520 flow meter. Pressure differential is measured using a Dwyer 477-5 series digital manometer. Voltage is measure at the pump plug to eliminate vdroop. Power and Amperage is measured using my Mastech power supply.

5 lbs!

It’s a heavyweight! All 5 pounds of it when loaded..wow! This is a tribute to the massive machined acetal block construction.

452 Volute Area

Volute Area
402 Series

452 Volute Area

452 Series

This picture shows removal of the machined block off plate for two pumps on the 402 model. The reservoir comes with this installed so you can run one pump and upgrade later to two pumps if needed. It also comes with G1/4 plugs on the back. If you remove the reservoir side plug, you can use both reservoirs for one pump. Many operational options exist within. I’ll include some configuration options later in the review.

402 Pump Block Off Plate

3/4" Compression Fitting Clearance Check

The 452 series uses large aluminum threaded couplers to screw the pumps into place (These are not in contact with water). This photo also provides a quick look at 3/4″ (19mm) OD compression fitting spacing:

More internal pictures – Very easy to take apart and clean or modified as needed:

Ok, that’s enough of looking at the components, it’s time to look at performance next:

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  1. PunkNugget says:

    Hey Martin,

    Just to let you know that since this morning, when I turned on the motors, I was able to see that left bay fluid lowered quite a bit and also noticed very fewer air bubbles flowing in the tubes. I topped it off as you suggested and will continue to monitor it for rest of the day as I’m building around the system. I’m looking to getting this case finally finished after 3+ months of waiting. Thanks again for the input, later… 🙂

  2. squigly says:

    Hey Martin,

    I have seen a lot of talk about using low speed pumps for the res and high speeds for the blocks, Which to me makes sense. I was wondering what your take on this is?

    I am expecting my RP-402×2 rev 2.0 shortly and was thinking of utilizing the single res with dual loop setup you showed. The difference being that the one loop would only contain the three rad’s and have the pump set to its lowest speed while the other loop would be for the CPU and 2 GPU blocks with the pump set to its highest speed.

    The thinking is to allow the coolant to dump as much heat as possible through the slow “rad” loop while not heating to much through the high speed “block” loop.. My concern is that if the coolant is travelling through 3 blocks in series the last device may really not be getting much out of the cooling solution..

    Your thoughts??

    • Martinm210 says:

      The whole “Slow Speed Through The Rad” concept is a false myth that comes up rather regularly and completely miss the reality that the time spent in the radiator over many “Cycles” is the same no matter what the speed is and the cooling doesn’t happen in one cycle, it occurs repeated over many cycles until equilibrium is met. Radiators will always perform better with higher flow rates, but at the same time the differences are really small and hard to measure.

      Regarding temperature differential across multiple blocks, again the higher the flow rate the less rise. Most systems will not see more than 1 degree difference in water temperature across the entire system and many with single block loops may see as little as .2C. This depends on heat load and flow rate. If you had a huge triSLI 700Watt heat load and low flow rates you might see a couple of degrees depending on the setup, but it too is still not make or break.

      Bottom line, slow flow rate is never better, and high flow is good but not a ton better either. Generally the only time low flow rate becomes a real problem is with inverted raditors and complex loops where the flow is too low to properly bleed the system of air. On those systems you could end up with a large pocket of air stuck somewhere that could cause performance problems in the radiator or block.

  3. Patrick says:

    Hello Martin,
    Great website and great reviews.
    I’m looking to set up a new watercooling build for Intel 3930K and two GTX570 cards.
    Going to use XSPC 360 rad, XSPC raystorm CPU block, EK-FC GTX580 waterblocks.
    So probably pretty low resistance.
    Want to overclock both the CPU and GPU’s but with 24/7 safety limits.

    I’m looking first for very quiet and next for good temps.

    After reading a lot I have 2 difficult points that i would like to ask your opnion on:

    first the combo pump+reservoir:
    one option is PMP-450 pump with bitspower mod pump top combined with EK Bay spin reservoir in acetal
    a variation here would be dual PMP-450 pumps with dual mod pump top

    second is dual PMP-450 pumps with the here reviewed Koolance RP-452X2 reservoir (by now available in REV 2)

    do i need dual pumps with my setup ?
    will there be a noticable difference in sound between seperate pump(s)/reservoir versus combined pumps/reservoir

    benefits for combining them that i see are:
    simpeler and cleaner loop setup
    pump redundancy with a serial setup

    going back and forth between them and really would like to have opnion of somebody with years of experience

    second connections:
    i want to use the Koolance VL3N quick disconnects in my entire loop. Some normal compression fittings will be used but i want to be able to take out each component out of the loop without the need to bleed it (ranging from 4 to 6 disconnect depending on combination of pump/reservoir).

    based on your testing i think this would not give any problems for my flow rate ?
    do you think it would be possible to fill all the components up seperately in this setup with cooling liquid, filling the reservoir, connecting all and have virtually no bleeding to be done ?

    Would greatly appreciate all the feedback that you can give on these two topics.

  4. PunkNugget says:


    Maybe I can be of some help in this area, since I am (currently) the online record holder (so far) of having 12 Quick Disconnects (QCs) on my new system found here on the link (below):


    I can tell you that I have had quite a few conversations with Tim & James (at Koolance) and they were very direct in their own testing of this equipment stating that the flow rate is insignificant compared to connecting it traditionally.

    BTW, I had someone say this about my build:

    “…what bugs me more is the hosing… I know it’s a complex loop but I always believe that less hosing = higher flow = lowers temp and looks nicer. But I love the finishes!”

    My reply was this:

    Thanks for your thoughts. The only reason why I chose to use the amount of Tygon tubing for this particular build was because I did NOT want to directly connect one CPU to the other CPU; thus transferring more heat to the secondary CPU. With tons of input from Martin (at Martinsliquidlab) and about a dozen pro PC builders, it was mixed bag of info. About 65% – 70% said to separate the tubing to have one rad dedicated to the one CPU and then have the other rad dedicated to the other CPU.

    So the looping setup is as follows:

    Koolance Dual Bay/Dual Laing Pumps (in series)>4 Rad>CPU0 (1st CPU)>Mobo Waterblock>3 Rad>CPU1 (2nd CPU)>GPU Waterblock & round and round she goes…

    Again, I do understand the amount of tubing that I used and also losing some pressure as a result OVER directly connecting the 2 CPUs together. In the end it might be a total wash to shave off the 3C to 4C that I was looking for, having the tubing setup in it’s current state. In the end, even if it’s not giving the 2nd CPU any temp gains, I personally think it looks nicer as there’s more internal “guts” showing with the UV lighting bringing out more the green fluorescent brightness that I love as a result.

    In a 74F room my current temps are: CPU0 = 33C & CPU1 = 34C with 2 x X5650’s @ 4.0GHz. What’s odd to me (and nice at the same time), CPU1 is the CPU that gets more use than the secondary CPU (CPU0) and is usually on average (from the other forum websites that I’ve been following) it’s 10C hotter. But not in this case. So maybe my current tubing setup has something to do with that. I’d like to think so, but in the end it works…

    So Patrick, I say all this to you because in the end I really believe you have to design it to make it work for you so you have the ease of use you’re looking for if you have to take something off and don’t want to take apart the whole machine just to get to one part that is in the way of the hosing. Even with my intricate hosing setup. I can QC everything with ease and reach ANY part if need be and then reconnect everything in a matter minutes. The benefits to me far outweigh what tiny little bit of flow rate that “might” be affected. Hope this helps. Later… PNugg… 🙂

    PS – Martin was one of the main PC builders that I sought input from before I put THE HACKINBEAST together…

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