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Thermaltake BigWater 760i

Date: January 22, 2008
Author(s): Rory Buszka

If you thought about liquid-cooling your PC, but were put off by the complexity of a typical installation, Thermaltake’s BigWater 760i may be the solution for you. The drive-bay mounting system is a novel solution, but can it provide enough of an advantage over air-cooling to make it worthwhile?


For a long time now, a water-cooled rig has been a status symbol of sorts – the calling card of a true enthusiast on the lunatic fringe of performance computing. A well-designed water cooling setup can have significantly higher thermal capacity than even the best air-coolers, and radiators may be placed remotely – even externally – which lets them take advantage of cooler incoming air.

Water cooling systems are also scalable; system designers can connect multiple CPUs, GPUs, and even the motherboard’s chipset to the coolant loop. Also, some water-cooling systems are designed to operate in complete silence, with massive external heatsinks that operate passively, and acoustically-isolated pumps. One such system is the Zalman Reserator.

Liquid-cooling offers some more fundamental thermal advantages over straight air-cooling, however. Water has a higher specific heat capacity than air, which means that the coolant absorbs more energy per degree of temperature rise than air does. That means there’s a greater temperature differential between the fluid and the heat-producing component, so a bulky heatsink cooler can be replaced with a compact water block, and the greater thermal conductivity of the coolant means that the heat transfer to a liquid coolant is almost 25 times more effective than direct transmission to air.

Still, all of that heat needs to be released to the air eventually, or else the benefits of water cooling evaporate, so water-cooled rigs use large radiators and fans to blow away the heat quietly.

Water cooling also has some serious drawbacks that make it impractical for many applications, reserving it for only the most extreme thermal solutions. First of all, water-based coolant solutions are electrically conductive, so if a tubing connection should fail or a reservoir should happen to leak, extensive damage can be done to the electronic components of the PC.

Secondly, setup of a water-cooling system can be extremely complex and involved, and requires proper planning of tubing routes and lengths, radiator capacities, and pump flow rates. Liquid cooling systems also require some maintenance, due to bacteria, mold, and algae growth in the fluid. Lastly, if you’ve elected to go with an external water cooling system, transporting your rig can become cumbersome and inconvenient, and potentially hazardous.

The product I’m looking at in this article hopes to solve some of these drawbacks that make water-cooling less-than-practical in many cases. The Thermaltake BigWater 760i is a self-contained water cooling system with a pump, reservoir, and 120mm-square radiator that occupies the space of two 5.25″ drive bays.

It’s part of Thermaltake’s BigWater series of packaged water-cooling systems that include everything you need to assemble a complete water-cooling loop in your case. The BigWater 760i’s drive bay mounting system is a novel concept – while we’ve seen other self-contained systems with similar specifications, they’ve been mounted externally.

Thermaltake is no stranger to the enthusiast water-cooling market, with an exceedingly broad range of water-cooling products that range from cases with pre-installed water-cooling systems, to a broad range of individual liquid cooling system components, and even enormous external radiator systems. With the BigWater 760i, Thermaltake emphasizes simplicity and modularity. However, can the BigWater 760i offer enough of a performance improvement over enthusiast air-cooling solutions to earn its keep and make it an attractive alternative? We’ll soon find out.

Packaging & Specifications

With the Thermaltake BigWater 760i, simplicity is the goal. Everything you need to get started, ostensibly, comes in the box, so it’s a big one. It’s glossy and colorful, depicting the system’s features and specifications in detail. I’m glad Thermaltake chose to put all that extra space on the box to good use, instead of wasting it with a cartoon character…or something. The cardboard is sturdy, and the packaging has the feel of quality.

Upon opening the box, we’re greeted with a large yellow piece of paper, admonishing us to fill and run-test the system outside of a case, in order to check for leaks before assembling it in the case and potentially destroying components with leakage. We wouldn’t want that.

Here’s what you get with the BigWater 760i kit: The radiator module, a copper water-block, plenty of UV-reactive yellow tubing, mounting hardware for the water block, the instruction manual and maintenance schedule guides, and a 500-milliliter bottle of UV-reactive ethylene glycol-based coolant with a squeezable filler bottle. It’s everything you need to build a complete loop with a single water-block, but according to Thermaltake, you can even set the loop up to include other water-cooled components, like a GPU or northbridge water-block, which are sold separately.

Here’s a look at the specifications of the BigWater 760i system.

Model BigWater 760i
Thermaltake Part No. CL-W0121
Exterior Dimensions
(L x W x H, Radiator Unit)
232mm X 148.6mm X 85mm
Package Weight 1.3(kg)
Water Block Dimensions
(L x W x H)
58mm X 58mm X 35mm
Water Block Weight 311g
Water Block Material Copper
CPUs supported AMD Socket 939, AM2; Intel Socket 478, LGA 775
Water Block Material Copper
Pump Flow 500L/hr
Pump Motor 12V, Ceramic Bearing
Pump Life 80,000hr
Pump Noise 16 dBa
Radiator Material Aluminum
Fan Dimensions
(L x W x H)
120mm x 120mm x 25mm
Fan Motor 12V, Sleeve Bearing, 1200~2400 RPM, adjustable speed
Fan Noise 16~20dBa
Fan Life 40,000 Hr
Liquid Tank Capacity 130mL
Tubing Size 3/8″ (9.5mm ID)

With that, we will move onto our features overview.

Features Overview

Thermaltake’s BigWater 760i is a fully self-contained water cooling system that fits into the space of two 5.25″ drive bays, with only a pair of tubes running to the CPU water block, greatly simplifying installation. Here’s a look at the BigWater’s features, as well as the installation process.

The BigWater 760i’s main unit contains the pump, reservoir, radiator, and fan. The radiator fan is a 120x25mm size, and features blue LED illumination and continuously-adjustable speed control via a small potentiometer that’s bundled together with the power supply connections. The pump is essentially the same as what’s included with Thermaltake’s AquaBay M5 system, except it’s hard-mounted to the chassis and to the reservoir.

The BigWater’s radiator is an aluminum “motorsports”-style design, featuring louvered fins and dimpled tubing to increase effectiveness without increasing weight. The louvered fins create turbulent airflow, causing more of the moving air to be incident on the surfaces of the radiator instead of passing straight through. Similarly, the dimples in the surfaces of the radiator tubes create turbulent swirling of the fluid flow.

The water block included with the BigWater 760i is 100% copper, and assembled using a brazing process instead of soldering, for improved heat transfer between the bottom and top halves of the water block. The interior of the water block contains “micro channels”, which create turbulence in the fluid flow and increase the overall surface area through which heat exchange takes place.

One important area affecting heatsink and water block performance is the quality of the surface finish on the base. Thermal paste is meant to fill microscopic gaps between the base of the thermal solution and the processor die itself, but direct contact is still the most effective means of transferring heat from a warm object to a cool object, and the fewer machining marks or grooves that exist on the base of the heatsink or water block, the better. The BigWater 760i’s water block has an exquisitely-finished base, polished to a mirror shine. Old Abe Lincoln’s head looked positively resplendent in the highly-scientific “penny test”.

Thermaltake has implemented a quick-disconnect system with the BigWater 760i, which is intended to simplify installation and removal of the system. The “no-spill” fittings allow the system to be quickly disconnected, but be aware that a small amount of fluid may remain in the connector itself. If you’ll be disconnecting this system frequently, have a glass ready to catch the excess fluid that might drip out.


Installing the BigWater 760i is somewhat more involved than installing an air-cooled heatsink. However, the process is well documented in the instruction manual, which is one of the better manuals I’ve yet seen from Thermaltake. Resist the urge to toss out the manual first-thing, because there are some subtleties to the process that can jeopardize the mission if they aren’t followed. In this review, I’m installing the BigWater 760i on a Socket AM2 motherboard.

The water block is held in place by Thermaltake’s signature H-style bracket. While mounting brackets like this one are par for the course with most water cooling systems, a clip-style retention mechanism that uses the existing AM2 socket lugs would have been greatly preferred, if only for the sake of ease of installation. With the H-bracket, you’ll need to disassemble the existing bracket if you’re installing the water block on a Socket AM2 motherboard.

These photos show the steps in installing the water block bracket. As you can see, installing and removing the BigWater 760i’s water block is a bit more complicated than installing your typical heatsink, but the process is straightforward, and well-documented in the instruction manual.

The next order of business is to cut the UV-resistive tubing to the appropriate length. You can use pruning shears for this purpose, but a pair of sturdy scissors should work fine. I don’t recommend trying to use a safety cutter (a.k.a. “box cutter”) – I nearly cut myself twice before I discovered that scissors would leave a far cleaner edge than the one I was making. Once you’ve got your tubing lengths cut, install one end of each segment into the appropriate fitting on the water block, and tighten the fittings securely with a wrench. Remember, you’re dealing with water, and any mistakes here can be costly.

Finally, install the quick-connect fittings on the other ends of the tubes leading to the CPU water block. These fittings use barb-type connections, but tubing clamps provide added security. Once you’ve finished this step, it’s time to fill and test the system.

Initial filling and testing of the BigWater 760i system should be done outside the case, to catch any problems such as weeping leaks, which could cause short circuits. Also, use this opportunity to coax any air bubbles in the system toward the reservoir, so they won’t impede the flow of fluid. Our test sample had a few droplets of liquid in its reservoir straight from the factory, where the unit was obviously tested with a fluid charge, but Thermaltake suggests this type of preliminary testing to ensure that nothing has been damaged in shipping, or missed by the QC process.

In spite of the sheer abundance of opportunities for a potentially catastrophic failure of the unit in preliminary testing, the only major problem encountered in the installation of the BigWater 760i system was space. The Cooler Master iTower 930 case that typically houses my hardware testing rig didn’t have enough clearance for the extended depth of the BigWater 760i’s radiator unit to fit. The only other option available was…

…this, a monstrous Thermaltake Mozart TX “Entertainment Center” case. No clearance issues here. In fact, nothing even close to resembling a lack of space. If this case isn’t big enough for your components, then a suitable one simply doesn’t exist. In retrospect, it’s not particularly surprising that the clunky design of the Cooler Master case had issues with fitting the BigWater 760i – the iTower contained so much superfluous sheet steel, it’s not even funny.

The part of the iTower that caused interference was the extended PSU mounting tray. If you’ve got a mid-sized case like the Thermaltake Armor, you’ve likely got enough space to install this unit comfortably. In the Mozart, the radiator unit was mounted in the lower group of four drive bays, occupying the central two. This left plenty of space above and below the unit to allow for air circulation.

Now that we’ve covered some of the considerations when it comes to installing the BigWater 760i, let’s see if our efforts are rewarded with superior cooling performance.

Thermal Performance and Noise

All heatsink testing at Techgage is performed with three considerations in mind: repeatability, accuracy, and comparison. In order to achieve these three aims, it’s important to use a standardized testing platform for all measurements which are to be compared.

In this case, the test platform is based around an AMD Athlon X2 “EE” model, which operates inside a 65-watt thermal envelope, similar to most Intel Core 2 Duo CPUs. What’s most important, however, is that the test platform be consistent in its operation, so that the thermal margins provided by each CPU cooler can be directly compared – since it’s the proportional change that we really care about.


The test system was originally designed to simulate the airflow of a typical enthusiast PC, minus any extraneous heat loads provided by a separate GPU, massive hard drive arrays, et cetera. However, in testing with a separate discrete GPU installed, it was found that significantly higher CPU temperatures under load were attainable with our particular type of stress test, indicating that the IGP was actually limiting the heat generation potential of the CPU.

For this reason, effective immediately, the test system will be revised to contain a reference video card as well. New measurements made using this test platform are not comparable to previous measurements, so new measurements have been made of all CPU coolers used in comparison for this article.

In addition, it seems that as CPU coolers continue to push the cooling envelope, and compact all-in-one water cooling solutions gain popularity, necessitating a greater heat load, the current test system may be pushed into obsolescence in the near future because of its relatively small 65-watt heat load when compared to the nearly 130-watt heat load of modern quad-core CPUs.

For this review, the Thermaltake Mozart TX case was substituted for the Cooler Master iTower 930, due to space issues in accommodating the Thermaltake BigWater 760i’s radiator unit.


Before installing either the water block or the cooler, a ball bearing-sized drop of Arctic Silver was spread into a thin layer using the sharp edge of a razor blade. During testing, Cool N’ Quiet was disabled, as well as the board’s “Q-Fan” smart fan control. The system was first allowed to reach a stable idle temperature for about 30 minutes before testing was performed.

Then 3DMark 2006 was run with its default settings to load both cores, and the peak observed temperatures were recorded after about 30 minutes of continuous load (looping tests). Finally, the system was allowed to return again to a stable idle temperature, and the peak observed idle temperature was recorded.

I’m using APACK’s ZEROTherm NV120 “Nirvana” cooler as a reference in this test, because it represents just about the top of the heap in enthusiast air-cooling, outstripping the cooling ability of the Zalman CNPS9700 by a small margin. The Thermaltake BigWater 760i’s simple, integrated design is meant to compete with high-end air-cooling solutions, so this comparison makes sense.

While the Thermaltake BigWater 760i certainly holds its own in the testing, it failed to eke out a lead against the high-end air cooling solution under load. Water cooling systems can handle transient loads well, thanks to their higher thermal mass, so to eliminate this potential for error, the CPU was loaded continuously for about 30 minutes before making temperature readings.

That the BigWater 760i system didn’t offer a performance advantage over the high-end air cooler isn’t a nail in the BigWater 760i’s coffin, however. These temperatures are excellent for any thermal solution, with the idle temperature being very near room temperature. The BigWater 760i definitely gets the job done.


The BigWater 760i has two major noise- and vibration-producing components. The pump itself is a significant source of vibration, though it does not generate much in the way of acoustic noise. If it’s not rigidly mounted, however, it can generate a low hum that resonates throughout the metal case.

The 120mm fan mounted to the radiator is still plainly audible even at its lowest speed, with audible turbulence and motor noise, though at high speed, blade noise dominates the sonic signature. In addition, the radiator unit emanates the sound of flowing coolant which, while soothing, isn’t silence. I can’t recommend this product for a ‘silent’ PC, though it may find a home in a ‘low noise’ system.

Final Thoughts

Thermaltake’s BigWater 760i is an intriguing product on a number of levels. It offers the simplicity of external water-cooling systems, but in a design that can be internally mounted. I personally know more than one enthusiast with extra 5.25″ drive bays to spare, and Thermaltake’s bay-mounted concept provides a way to make good use of that space, instead of letting it go to waste.

The BigWater 760i is a robust thermal solution in its own right – while it didn’t shatter the record held by the ZEROtherm Nirvana cooler I reviewed in November of 2007, it delivered performance that’s definitely on-par with the best air-cooling solutions out there.

There were a few things I found less than encouraging about the BigWater 760i, besides the fact that it failed to unseat the reigning champion in air-cooling. First of all, the water block and mounting bracket require extensive assembly, when a simple clip-style or push-pin mounting system would have streamlined the installation process immensely.

As it stands, you can’t install the BigWater 760i without removing the motherboard from the case. In addition, the chassis of the radiator unit felt flimsy and cheap, and I would have preferred to see the front of the unit completely enclosed in mesh, instead of just a tiny window through which to view the fan’s illumination. A full-face grille would improve the unit’s performance in worst-case scenarios where the drive bays above and below the radiator unit are occupied.

What really saves the BigWater 760i, in my mind, is its simplicity and overall cool-factor. I mean, c’mon, it’s a water-cooling setup that doesn’t dominate your entire case. And it’s expandable, so you can plumb in additional water blocks for your VGA cards, chipset, hard drives, memory, and anything else that’s being water-cooled these days.

If you want to really take things to an extreme, you could theoretically add additional radiators to the system. Its performance is on par with the best air-cooling out there, but it’s got undeniable appeal simply for the fact that with only an afternoon’s worth of work, you too can join the water-cooling club. I’m awarding the Thermaltake BigWater a Techgage score of 7.

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