Aesthetic Water Cooling Solutions: Zalman Reserator 1, ZM-WB2 Gold and ZM-GWB1

So, the Zalman Reservoir 1 water-cooling system is not only a high-quality and finished product, boasting a completely noiseless operation and effective appearance, but it is also an excellent foundation for building your custom-made water-cooling system, which would add new features to those of Reservoir 1 proper.

by Tim Tscheblockov
09/15/2004 | 03:22 AM

Zalman Tech has always been at the forefront of progress in noiseless PC cooling. This tradition continues with the Zalman Reserator 1 water-cooling system I am going to give a look to in this review. The idea of cooling the hottest PC components with the help of water is not new, and it’s hard to come up with anything revolutionary in this area. On the other hand, Zalman is Zalman and their water-cooling solution must be non-standard, at the very least.


Let us see then, what ideas are implemented in Reserator 1, and with what outcome – how efficient it is in practice.

Zalman Reserator 1

All water-cooling systems share the same basic design: a closed contour with water circulating within. Taking heat from the processor in a special block, the water arrives to a radiator to spread this heat out in air. Several water blocks can be installed, if necessary, for example on the CPU, GPU, chipset’s North Bridge and so on.

The temperature of the water rises but slightly, by a fraction of one degree, after each water block, so the sequence of the units plays no big role. For example, a “CPU-GPU-heatsink-pump-CPU” chain would be equivalent to a “CPU-pump-heatsink-GPU-CPU” combination in most cases. Choose what’s more convenient as the fundamental advantage of water-based cooling remains with you – unlike with an ordinary air cooler, it is not necessary to transfer heat to air “on the spot”. Heat can be taken by and moved with water to where it can be effectively dissipated in the surrounding air.

The coolant in water-cooling systems is usually cooled down in a special radiator with thin ribs at which an air fan is blowing. The radiator can be placed either inside the system case (in this design, the fan blows at it and also exhausts the hot air) or outside, in an independent unit, attached to the system case with tubes.

So, it is obvious that water-cooling systems produce much less noise than ordinary air coolers of the same efficiency. The fan on the water radiator can be made low-speed, while the pump is completely noiseless. It generates a certain vibration, but you can easily get rid of it.

It seems like this scheme cannot be improved further, and all modifications will only concern the construction of the pump, water blocks, and the radiator. Well, Zalman is of another opinion.

The main component of the Reserator 1 system combines a reservoir with a pump and a radiator, hence the name (Reservoir + Radiator = Reserator). The system is fanless, i.e. completely noiseless.

The appearance of Reserator 1, basically a ribbed pole on a round stand, is most impressive:

The following snapshot allows you to compare its size with that of a standard PC case:

And here’s how a compact-disc compares with the stand:

The Reserator is a ribbed aluminum tube with a submersible pump, located at the bottom, next to the nozzles. The pump is driving water out of the reservoir towards the output nozzle. The water then takes a trip through one or several water blocks and returns to the reservoir through the input nozzle and mixes with the rest of the water.

The pump is no impressive construction – it seems to lack muscle. You can its photo on this page of Zalman’s website. Unfortunately, I can’t show you a photo of my own: the main “tube” of the Reserator is fastened with a thread and a rubber gasket at the bottom, i.e. where the pump is. This is all so tightly drawn up that I couldn’t unscrew this tube from its bottom.

Well, even given the pump is not a very powerful gadget, this is compensated by the CPU water block’s offering little resistance towards the stream of water. All the nozzles and tubes have a rather big section, thus also making it easier to pump water through.

The maximum volume of water the system can take in is 2.5l. If you pour in this amount, water fills Reserator 1 and contacts almost all of its internal surface. The ribs on the outside of the reservoir efficiently dissipate heat in air even without additional blowing: the outside surface area is 1.274 sq. m, according to Zalman.

The cap of the Reserator is fastened on a thread with a rubber gasket. With all its gaskets, the system is not completely hermetic. There’s a small hole in the center of the cap, which helps to avoid pressure changes in the system when it heats up or cools down.

The basic characteristics of Zalman’s Reserator 1 are listed on the cap:

The pump is powered from a 220VAC source; the power cable with an unassumingly-looking switch in the middle comes out of the reservoir.

I think that having made so original a water-cooling system, the Zalman engineers could have invented something more interesting than a banal switch. That’s a trifle, of course, but trifles matter, too.

Now, let’s examine the remaining components of the water-cooling system from Zalman.

The ZM-WB2 CPU water block, shipping with the Reserator 1, consists of an aluminum casing with a pressed-in copper core: its external side contacts with the CPU surface and the internal side has circular grooves for better heat transfer to the coolant. The anodized aluminum casing has the same color as the reservoir; it has threaded holes you screw the nozzles into. The rubber gaskets prevent any leakages.

Then, silicone tubes are fastened on the threaded nozzles with the help of threaded fittings – this solution is employed in a number of water-cooling systems. The next snapshot is an illustration of the polish quality of the sole of the water block; it also shows one such fitting:

The sole of the water block is not just smooth, which is easily achieved with chemical polishing and not necessarily an indication of high quality, but also almost perfectly flat, which is more important than nice mirror reflections on the smooth surface.

You can see the characteristic signs of contact with the heat-dissipating lid of the CPU. They indicate that the block’s sole only contacted the CPU around the rim, leaving circular traces as I was turning it around. In other words, the sole of the water block is not ideally flat, but rather concave. The gap between the sole and the screwdriver is visible on the snapshot below:

The fastenings of the water block are the same as you receive with Zalman’s ordinary CNPS 7000 series coolers. These plates and bars and bolts allow mounting the block on any modern processor: Intel Pentium 4, AMD Athlon/Duron/Athlon XP and Athlon 64. The following still life pictures all the fastening parts enclosed with the Reserator 1 system:

There are no silicone tubes on the snapshot as well as yet another interesting component of the system, its status indicator.

This flow indicator, with the same nozzles as the CPU water block has, is connected to the system in the same manner as the water block. If everything’s right – the pump is O.K. and the connecting tubes are not pinched anywhere – the bright plastic flag starts fluttering inside the glass tube of the indicator, showing that the water is circulating normally. If the system is off or something prevents a normal water-flow, the flag is asleep.

We received the Reserator 1 system along with the ZM-GWB1 kit, purchased optionally. The following section of the review deals with it.

Zalman ZM-GWB1

The ZM-GWB1 is not just a water block for the graphics processor, but rather a cooling kit for the GPU as well as the memory chips on the graphics card.

The kit consists of two water blocks, eight heatsinks with sticky thermal pads for the memory chips, fastenings, a small tube with thermal paste and a screwdriver.

The water blocks look alike. The longer of them fits for almost any graphics processor, and the shorter is intended for GPUs with a protective frame around the die, for example for RADEON 9700/9800 series chips. Thanks to the well-designed fastening system, the water blocks can mount on nearly every graphics card. The only requirement to the card is its PCB must have suitable holes near the GPU.

Although the nozzles the connecting silicone tubes are attached to don’t look assuring, the tubes do hold tight– it’s hard to take a tube off such a water block without a serious effort.

The internal structure of the water blocks is disgustingly oversimplified: there are no grooves, cavities or ribs to improve heat transfer to the water stream. Instead, there’s just a trivial through hole that comes straight from one nozzle to the other:

I must confess I hadn’t expected anything like that from Zalman. Without running any tests, I can already express my doubts about the efficiency of such water blocks. First, the sole surface of the blocks is not treated at all. Thermal paste can improve this somewhat, filling in the micro-caverns on the anodized surface, but some polishing off would anyway help a lot. Second, the heat from the graphics processor is not transferred through a copper base, like in Zalman’s own CPU water block, but rather through a thick layer of aluminum, which has twice worse heat conductivity characteristics. Lastly, a through and round hole is the worst channel for the water stream. Such a channel has the smallest internal surface area, i.e. this is the worst case for heat transfer.

It is good the ZM-GWB1 doesn’t come with Reserator 1 – it wouldn’t do to spoil such a nice system with a bad GPU water block.


The putting-together of all the components of the system shouldn’t cause you any big trouble. The first thing to take care of is the tubes and the threaded fittings – the tube is always trying to turn around with the fitting, and after a couple of such rotations the tube goes all twisted circles and figure-of-eights. To avoid this, hold the tube with one hand and tighten the fitting with another. Not very convenient, you know.

The second thing to care about is the nozzles on the reservoir. It’s easy to cut a slice or two of the skin from your own fingers with the rather sharp bottom edge of the Reserator when tightening the threaded fittings. To protect the integrator, the manufacturer might have lifted up the bottom edge of the ribs above the nozzles, or smooth it out.

Otherwise, the assembly should go on effortlessly: connect all the components in the convenient order…

…and mount the water block on the central processor.

The system is filled with water and powered on. You hear a gurgle for a couple of seconds as the water is filling all of the system components, then silence. The flag is quivering in the water stream indicator; it means the system is working normally. It’s time to test it.

Well, no. Let us first attach the water block of the graphics processor. I shut the system down and clinch one tube with special clamps enclosed with Zalman’s Reserator 1 – they will prevent any leakages. Then I cut the tube up between the clamps, take the graphics card, mount the water block on it – this is very easily done – and attach the ends of the cut tube to the nozzles of the water block:

Then I remove the clamps and turn the system on. It is now really ready for my tests.

Testbed and Methods

I tested the Zalman Reserator 1 system and the ZM-GWB1 water block on a testbed configured as follows:

The Pentium 4 overclocked to 3.6GHz generates quite an amount of heat even without a core voltage increase, while the GeForce FX 5900 Ultra graphics card consumes more power and dissipates more heat than the RADEON X800 Pro or GeForce 6800 GT, and slightly less than the RADEON X800 XT Platinum Edition. Thus, I put the Zalman Reserator 1 system accompanied with the ZM-GWB1 block in a very harsh operating environment.

I performed my tests in the following manner: first, I started the system up and left it idle for 2.5 hours (the Windows XP Desktop was on the screen). Then I launched programs that loaded the CPU and the graphics card and watched the temperatures change for 2.5 hours more.

I used the latest version of the Motherboard Monitor to read the CPU temperature and RivaTuner to read the GPU temperature. The temperature of the water in the Reserator and of the room air was measured with a Fluke 54-II thermometer.

I used the CPU water block alone in my first test and loaded the CPU with two copies of the BurnP6 utility. The X-axis of the following graph contains the time passed since the launch of BurnP6 (in minutes); the Y-axis shows the temperature.

Well, 28°C in the Idle mode and 48°C in the Burn mode are good CPU temperatures. You may note that the temperatures of the water and the CPU were rising simultaneously; the difference between them was almost constant, about 8°C.

Note also the level of the water temperature in the system: it went up rather quickly, but the rate diminished as the temperature had become higher. This is explained by the fact that the difference in the temperatures of the room air and the surface of the Reserator becomes bigger as the water temperature increases, and this facilitates the transfer of heat to air. The water in the system heats up till the system becomes balanced at a given temperature – the amount of heat generated by the CPU equals the amount of heat given out to the outside air.

“Heating” the system up for 2.5 hours, I nearly reached the equilibrium – the water temperature had only increased by 0.3°C in the last half an hour. I say “nearly” because the system with its 6.5kg of aluminum and 2.5l of water has a tremendous thermal inertia. Evidently, the CPU load is going to be smaller in a majority of real-life applications than with special-purpose CPU-grilling programs, and the temperature of the processor is going to be lower, too. The same goes for a short-term peak load – the system won’t heat up in so short a time, so the CPU temperature won’t reach the values I got in my tests.

For my second test, I connected the GPU water block into the system and ran a bot-match in the onslaught mode on the Torlan level of Unreal Tournament 2004. This test is a good heater of both the CPU and the graphics card. I selected the maximum image quality settings in the game, 1600x1200 resolution, 4x full-screen antialiasing and 8x anisotropic filtering.

The rest of the test conditions were the same: 2.5 hours of idleness and then 2.5 hours of Unreal Tournament 2004. The results follow below:

The CPU was less hot than in the previous tests, and it is no surprise since the calculations of physics and game logics in Unreal Tournament 2004 are a smaller load on the CPU than a special-purpose maximum-load utility produces. However, the GPU and the CPU, working together, generate more heat than in the previous test: the temperature of the water after 2.5 hours of heat-up was higher than in the first test.

The GPU temperature measurements confirm my above-said suspicions: the GPU water block doesn’t suit well for its job. Those 80-90°C of the GPU temperature are not satisfactory, to put it mildly.


I’d like to say about bad things first. The ZM-GWB1 kit should only be used with low-power graphics cards. The GPU temperature on cards of the GeForce FX 5900 Ultra class and hotter may become critical with the ZM-GWB1.

The Zalman Reserator 1 system, on the contrary, leaves a very positive impression with its impressive looks, noiseless operation, and high efficiency. Well, if desired, you of course can find faults with it like the heavy weight, big dimensions and “external” placement of the radiator (or rather radiator-reservoir), but you have to put up with that anyway. A smaller and lighter system wouldn’t be as efficient.

Reserator 1 can become a foundation for a non-standard cooling system assembled to the user’s taste. The system permits using any water blocks, not necessarily manufactured by Zalman, so you can use third-party blocks for the chipset or the GPU, or instead of the standard CPU block (although the latter is unlikely – the standard block is all right). The Reserator won’t become any worse for such an adjustment. The only requirement to the third-party water blocks is they have to have similar-section connecting tubes.

In order for the low-power pump of the Reserator to work effectively, you should select water blocks with the minimal resistance to the water stream. Well, extreme people can always replace the standard pump with a stronger one.

So, the Zalman Reservoir 1 water-cooling system is not only a high-quality and finished product, boasting a completely noiseless operation and effective appearance, but it is also an excellent foundation for building your custom-made water-cooling system, which would add new features to those of Reservoir 1 proper.