Perfect Silence: Zalman Reserator 2 Fanless Liquid-Cooling System Review

We are about to check out the second version of Zalman’s liquid cooling system. Silent operation being its highlighted feature, what about its cooling performance proper? Let’s find out how much more efficient has Zalman Reserator 2 become from our detailed review!

by Sergey Lepilov
04/25/2007 | 09:59 AM

In 2005 we published Zalman Reserator 1 Plus Liquid Cooling System Review. That liquid cooling solution did not leave PC enthusiasts indifferent, gathering both positive and negative reports from users. First showcased at Computex 2006, the new Zalman Reserator 2 continues the series of silent liquid cooling systems from the renowned Korean brand.


Let’s check it out now.

Closer Look at Zalman Reserator 2

Package and Accessories

The product packaging raises associations with Matreshka, the Russian nesting doll. First, there is one cardboard box the size of a PC case. The paper sticker on it tells you the product model and power requirements.

There is another box inside it – this one is made of thick colorful cardboard:

The text on the sides of the box tells you diverse information about the cooler’s features, accessories, specification, etc.

You can unpack the box to find another one (a third one!), which is made of foam plastic.

On top of that box there is a flexible pipe, 4 meters long, and a user manual in English and Chinese.

The foam-plastic frame has two tiers. One tier accommodates main components of the system.

Here they are from left to right and from top to bottom:

We can now have a closer look at the smaller components:

The bottle with anti-corrosion coolant is 250 milliliters large:


The sticker on the bottle tells you that the coolant consists of propylene glycol with some anti-corrosion additive. The coolant retains its properties for 1 year and its freezing point is -9°C. I’ll tell you below how to use this coolant properly.

Here’s the mentioned user manual:

And this is the 4-meter-long pipe with an inner diameter of 8mm and with 2mm walls:

The pipe is soft and flexible, which makes the assembly process much easier. Besides the manufacturer’s name there are marks set on it every centimeter for easier measuring. Running a little ahead, I want to say that I had about 1.5 meters of pipe left after I had assembled the system. Zalman measured pipe out with a generous reserve.

Reserator 2 Main Block

The main block of the system lies in the second tier of the foam-plastic box. Here it is:

The Reserator 2 is large if compared with ordinary coolers: 369 x 436 x 76mm (height, length, width).

The Reserator 2 consists of three sections: a control unit with an indicator and Power/Reset button, a reservoir with a cap and fittings in the bottom part, and a radiator proper.


The radiator connecting both parts is painted pure black:

It has a lot of ribs along its entire length. The total dissipation area is as large as 1.5 square meters! For comparison, the Zalman CNPS9700 is only one third of that area. The main block of the Reserator weighs 7 kg.

There is a water flow indicator on the front side of the pole with the integrated control unit:

When the filled system is working, this indicator is rotating and is highlighted in blue, producing a rather irritating flicker at night. It is not conspicuous in the daytime. Unfortunately, it cannot be disabled.

Removing the cover of the control unit you can see a pipe that goes to the indicator and a small PCB with an integrated tweeter.

The back pole – the reservoir – is made from aluminum and ribbed as well. Its bottom part has two fittings with valves and locks:

The cap of this pole can be removed, too. Inside it you can see a submersible pump Eheim:

According to the specification, the pump performance is 300lph and its head pressure is only 0.5m. These are rather modest characteristics, but installing a more powerful pump would perhaps increase the noise level which does not go well with the product concept.

CPU Water-Block: Zalman ZM-WB4 Gold

The new water-block ZM-WB4 Gold is included into the box in a separate package. It can actually be bought separately. The transparent package allows you to scrutinize the thing without taking it out.


Besides the water-block and braces, there is a small box with accessories. The back side of that box shows the way to install the water-block on the supported CPU sockets.

Here’s everything you will find in the box:

The water-block has a gold-sputtered copper base. It has a needle-shaped interior design with additional grooves in the base.

The needles are square in profile. This is easier to manufacture than cylindrical needles, but the circulation of liquid is worse with this design. There are a total of 196 needles (12 x 12) placed 1mm apart, the width of one side is about 1mm. The plate is covered from above with a transparent polycarbonate cap with two fittings. The specification says the fittings are compatible with the following pipe diameters: 14x10mm, 13x10mm, 13x9mm, 12x9mm, 12x8mm, 11x8mm, 10x8mm (internal x external diameter). Two threaded barrels are inserted into the polycarbonate on both sides of the central fitting. These are necessary for attaching mounting clips. The water-block weighs a mere 135g.

Its base is absolutely flat and finished perfectly:

The included manual describes the installation process thoroughly, but the procedure is anyway very simple and intuitive. The Zalman ZM-WB4 Gold can be installed on every modern CPU socket, save for the hopelessly outdated Socket A (462). You should first attach adjustable-length fastening clips to the water-block and then fasten them with included screws either to the plastic LGA775 frame you have installed beforehand (you need to take the mainboard out of the system case for that) or to the back-plate barrels on Socket 754/939/940. A pressure clip fastened to the plastic socket frame is used to mount the water-block on Socket AM2.

Installed on an LGA775 mainboard, the water-block looks like this:

Thanks to symmetrical holes around LGA775 the water-block can be oriented freely, but only one orientation is possible for mainboards for K8 CPUs. This is a significant drawback I’ll tell you more about in the Assembly section below. Here is a link to the water-block installation guide (a PDF file).

VGA Water-Block: Zalman ZM-GWB3

The included ZM-GWB3 VGA water block is also selling separately, like the CPU water-block, and so it comes in its own individual package, small and neat:


The package is designed like that of the ZM-WB4 Gold: transparent plastic with a detailed installation guide on the reverse side. There are accessories in the top part of the box. The kit includes:

The universal VGA water-block Zalman ZM-GWB3 is made from aluminum:

The pair of fittings going out of the water-block can be turned around freely for easier assembly and free orientation of the pipes inside the system case. According to the manufacturer, the water-block has the same design as the CPU water-block ZM-WB4 Gold (perhaps with fewer needles due to the smaller base area). The water-block weighs only 100g.

The aluminum base is flat, but the manufacturer should have polished it off better:

The Zalman ZM-GWB3 is compatible with most of modern graphics card models. Just take a look at the following scheme and table:

So, the water-block cannot be installed on the GeForce 7950 GX2 due to obvious reasons and will be useless on GeForce 8800 series cards due to its too small base area.

I installed it on a GeForce 7600 GT for my tests. To do that, I first put rubber circles on the fastening barrels and inserted them into the holes in the graphics card PCB.

The barrels are fastened at the reverse side of the PCB with spring-loaded thumb nuts through plastic spacers:

Then you just fasten the water-block with screws to the installed barrels.

You can refer to the official manual in PDF format for details.

Assembly Tips

The assembly process is described in detail in the included manual, yet there are some things that need a special mention.

First of all, you should attach the included feet to the radiator:

The feet have rubber soles so that the radiator didn’t scratch the surface you put it on.

Next, you connect the input and output fittings with the included pump-up pipe, pour the coolant (you should dilute the concentrate with water in 1:4 proportion) and pump the system through:

This seems to be simple in the photographs: the pipe was empty, but now is full. Well, it’s not as simple as it seems. Besides being powered from a wall outlet, the Reserator 2 is also connected to a Molex connector of your PSU. But it’s not convenient to start the system case up when you are pumping the Reserator through and the computer is dismantled. Zalman included a closing wire you can plug into the PSU’s 24-pin power plug (to the green and black contacts) to wake the PSU up so that it sent power to its Molex connectors.

It’s simpler if you haven’t yet dismantled your computer and installed the CPU and VGA water-blocks – you can just pump the Reserator 2 up by simply starting your PSU.

The pumping-up process is illustrated thus:

Take note that you have to tilt the radiator by 70 degrees from the vertical to fill in all the hollows in it. It’s only after that that all air will leave the system and the pump will begin to move the coolant around. If the liquid is not being pumped through, the system protection wakes up, emitting a warning sound and shutting the system down. If this happens to you, make sure you’ve done everything right and restart the system, tilting the radiator again.

When this is done over with, you disconnect the short pipe from the radiator (the fittings have valves that prevent liquid from leaking out of the radiator as well as out of the pipes) and take off the fittings from it. The fittings sit so tight that I had to cut the ends of the pipe to take them off.

Then you should decide upon the place of the radiator and your system case. The manufacturer mentions this specifically in the manual:

It is recommended that the radiator be placed on the same level with the PC case. Not higher or lower.

I had to put pieces of foam plastic under the radiator to lift it up to the necessary level. But good for me, the Reserator 2 is a perfect match to the design style of the ASUS Ascot 6AR2-B system case.

After you’ve made up your mind as to the position of the radiator, you should measure and cut up the connecting pipes. Then, put the pipes through the included bracket for the back panel of your system case, get their ends on the fittings of the water-blocks and fasten them with braces. Then you insert the fittings you have taken from the pump-up pipe into the ends of the pipes you have put out of the system case for the radiator and close the system. The manufacturer recommends that the liquid from the output fitting (and the appropriate pipe) go to the CPU.

Assembled and filled up, the system looks quite aesthetically inside the system case, to my mind:

The system case seems uncommonly roomy after gigantic super-coolers. You’ve got free access to every component. Unfortunately, the manufacturer didn’t provide anything to cool the near-socket space on the mainboard, but in my system case that was performed successfully by a 120mm fan installed on the side panel opposite the CPU socket.

Next I started the system up. The Reserator woke up with a barely audible squeak. The water flow indicator on the front panel began to rotate, but somewhat languidly, to my mind. And really, when I saw how slowly the pipes and the CPU water-block were being filled up, I realized the pump was indeed too weak. Moreover, take a look at the CPU water-block:

It is empty by a third! If the pump were twice its actual capacity, this emptiness might be avoided. Fortunately, this problem is easily solved on the LGA775 platform by simply turning the water-block in such a way that the output pipe is higher than the input one:

But what about users of mainboards for K8 processors whose CPU mounting frame is in parallel to the back panel of the case, which is quite a common thing. Well, there is nothing you do about that. You have to put up with the emptiness and, consequently, loss of efficiency unless you replace the water-block.

This is the payment for silent operation which is emphasized by the developer as the main feature of the Reserator 2. Installing a more powerful pump would inevitably increase its noise. To be more exact, it would make the system audible. By the way, the user manual included with the Reserator points at the opportunity to install an external pump into the circuit.

As for noise, it is totally missing here. The coolant does not babble in the pipes and radiator while the pump is silent. Telling you the truth, you can hear it, but only if you comply with five requirements: 1. say your neighbors to be quiet, 2. shut up all the doors and windows in your room, 3. disable all the system fans and, desirably, the PSU fan, 4. disable HDDs, 5. lie down next to the radiator and put your ear to the bottom of the aluminum pole the pump resides in. It is only then that you will hear it! So, the term noise just cannot be seriously applied to this liquid cooling system from Zalman.

I’ll show you its specs now and test it then.


The technical specs of Zalman’s water-cooling system are listed below.

Testbed and Methods

I think the Zalman Reserator 2 should be compared with a liquid cooling system or a high-performance air cooler. I didn’t have another liquid cooler at hand, but had plenty of super-coolers. Considering that the Reserator 2 features silent operation, I set the noise level from the opponent coolers to a minimum. The 120mm fan of the CPU cooler Enzotech Ultra-X was working at its lowest possible speed of 1130rpm (according to the monitoring tools), for details on the Enzotech Ultra-X cooler see our article called Scythe Andy Samurai Master and Enzotech Ultra-X Coolers vs. Overclocked CPUs. A Zalman VF900-Cu LED was installed on the graphics card to oppose Zalman’s water-block (for details see our article called Zalman VF900-Cu LED: New Universal VGA Cooler Review). It was set at its minimum 1380rpm, too. These two air coolers were audible, yet were very quiet at the said speeds.

The coolers were tested in a closed system case with the following configuration:

All tests are performed in Windows XP Professional Edition Service Pack 2. SpeedFan 4.32 is used to monitor the temperature of the CPUs, reading it from the CPU sensor. The mainboard’s automatic fan speed management is disabled for the time of the tests. The thermal throttling of the Intel Core 2 Duo processor is controlled with RightMark CPU Clock Utility version 2.2 (our processor begins to skip clock cycles on reaching a temperature of 81.5°C).

The CPU was heated by Intel Thermal Analysis Tool (TAT) according to the method described in our article called Originality or Efficiency? Cooler Master Mars, Eclipse and Hyper TX Cooling Solutions Reviewed. Considering that liquid cooling systems need a long time for the coolant to heat up fully in the circuit, I left the system working for 1 hour (instead of 18 minutes as usual) under 100% load for both CPU cores. The CPU temperature would stabilize after 35-40 minutes with the liquid cooling system. With the air super-cooler the CPU temperature would stabilize in 7-8 minutes after the start of the test.

The Game test mode was simulated by running the Firefly Forest test from 3DMark 2006 in a loop for an hour. Anisotropic filtering and full-screen antialiasing were not enabled.

I performed at least two cycles of tests in each mode (TAT and S&M) and waited for 25-30 minutes for the temperature inside the system case to stabilize before each test cycle. The maximum temperature in the two test cycles was considered as the final result (if the difference is not bigger than 1°C – otherwise the test is performed once again). Despite the stabilization period, the result of the second cycle was 0.5-1°C higher.

The ambient temperature was monitored by means of an electric thermometer and remained at 24.5°C during the tests.

Thermal Performance

The Intel Core 2 Duo E6400 stepping B2 processor was overclocked from its default 2133MHz to 3500MHz (a 64.1% frequency growth) with a core voltage increase to 1.45V.

I wrote above what I think about the weak pump of the discussed cooling system and the slow water flow in the pipes, so besides checking the Reserator 2 with its CPU and VGA water-blocks I also tested it when used for cooling the CPU alone (this is referred to as “CPU only” in the diagrams). The VGA water-block and connecting pipe was excluded from the system and replaced with a Zalman VF900-Cu LED in that test:

Now it’s time to take a look at the results:

Obviously, the Zalman Reserator 2 is inferior to the team consisting of an Enzotech Ultra-X and Zalman VF900-Cu LED in every mode, on the CPU as well as on the graphics card. The weak pump is the cause, and the test of the Reserator with only one CPU water-block is an indication of that. When the graphics card with its connecting pipe had been excluded from the system, the CPU was 5°C cooler in tests. I want to draw your attention to the fact that I used a rather cold graphics card, by today’s standards. I wonder what if I used something like Radeon X1950 XT/XTX?

The liquid cooling looks unimpressive on the graphics card, either. It is 3°C worse than an average low-mainstream-class air cooler. However, I’m going to be rather positive about the Zalman Reserator 2 in the following conclusion despite its having lost to its air-based opponents in my performance tests.


Let us try to see the second version of Zalman’s liquid cooling system from the point of view of its targeting. The Reserator 2 was developed to cool system case components silently. And it does accomplish that. The pump is perfectly silent inside the filled reservoir and that’s all! There is no other rotating, rubbing or rattling element in the discussed liquid cooling system. I don’t want to claim it has superior performance – the system ran about 4°C warmer than the best air super-cooler in my own tests, but this Reserator is not meant to bring you top performance. It is meant to bring you silence. Silence is the main criterion for you to consider the Zalman Reserator 2 as a great buy.

Besides that, you can optionally buy a couple of water-blocks to cool the graphics card’s memory (ZM-RWB1) and mainboard’s chipset (ZM-NWB1) and thus apply water cooling to every PC component with high heat dissipation. How is it going to affect CPU cooling efficiency? No doubt it will worsen, considering such a weak pump. I hope the manufacturer will perform its own tests with a pump that has at least two times the performance of the one included with the Reserator 2 now. Perhaps the tightly closed aluminum reservoir will allow increasing efficiency without a great increase in noise. The Zalman Reserator 2 will surely lose a large share of its appeal if it comes with a noisy pump, yet I think there is still some reserve for a more powerful, yet silently operating, pump left.

I also have no doubt that you can buy separate components for the money they ask for a Reserator 2 and assemble your own liquid cooling system with the same efficiency. But will it be as quiet as Zalman’s? Moreover, many users just don’t want to bother about selecting, searching for and assembling a custom-made liquid cooling system, so ready-made solutions still have a small, yet constant share of the market. And the Zalman Reserator 2 is going to deservedly enjoy its own share of that share.

Here are its pros and cons, in brief.