OCZ Hydroflow CPU Waterblock Review


Welcome to my review of the OCZ Hydroflow CPU water block designed for a wide range of processors.  This is an actual production run copy that comes standard with an LGA775 mount.

The above photo is the block itself with supplied 1/2" metal barbs, the kit include quality metal barbs in both 3/8" and 1/2" sizes

The sample product I'm testing here today was provide by Tony from OCZ.  You'll likely know OCZ from the wide array of quality product such as their well known memory modules and power supplies.  I myself have had the pleasure in owning an OCZ game-extreme 700 PSU that I've used for a couple of years now, and I've also had the a superb experience with their support section.  They are a very established company with an emphasis in customer support and entering the field of water cooling with this new Hydroflow water block.

I would also like to give special thanks to Gary from Sidewinder Computers for providing me with the Q6600 processor to test with. Check out Sidewinder for all your water cooling needs.

Block Characteristics

The block is the first block for OCZ so it is all new.  The design incorporates a two part copper/delrin block with stainless steel hold down, and a plethora of accessories.

My first order of review is looking at the packaging and accessories.  This is the box in which the block and accessories came in:

The box is about a 5" x 1.5" package and heavy as it's packed full of goodies, the block was shipped directly in this box.

Upon opening the box you realize why it was so heavy. I didn't however see any foam padding protection, but everything was individually wrapped and arrived at my door without damage even though it wasn't shipped in your typical box in a box style.  The first thing I noticed is the metal barbs in two sizes, this is one of only two blocks I've seen that sends both sizes in a nice metal barb.

This picture is with everything pulled out of the box.  As you can see, everything is nicely individually wrapped for protection.  It comes with the LGA775 hold down mounted on the block, and not only one, but TWO BACK PLATES!  While some companies make you buy a back plate separately or don't include one at all, OCZ has done everything they can to make sure you have what you need to install the block.  Also rather than cheap plastic barbs that you get with some blocks, this one comes with nice nickel plated brass barbs.  Also note that the OCZ Freeze tube you see on the upper right was a separate sample, there is however included a small packet of TIM compound noted in the lower left of the picture above.  Then you get Two sets of standoffs that are used in mounting the block differently than most I've seen, but it works very well. This is one of the more complete packages I've seen.


Here is a better view of the Universal hold back plate and hold down.  While many blocks have only one plate with all of holes in it, OCZ has given you two.  This maximizes the motherboard compatibility and gives you a cleaner look.  The universal hold down in the upper left is a very thick solid piece of steel and very rigid, it's much more rigid than most back plates and will provide you a great deal of motherboard protection.  In addition the hold down plates are both nicely finished.

You can easily take the block apart with the four allen bolts that run through the hold down plate, through the black nylon top, and into the copper bottom. This reveals the flow path is a corner to corner design similar to the Apogee GTX.  The base is a thick copper base with a unique Triangle shaped pin matrix specially designed to maximize scrubbing of the surfaces and turbulent flow.

Here is a closer look at those triangle shaped pins, they are very nicely machined with no evidence of copper burs to clean.

And the base is of the new "Stepped" style specifically designed to maximize pressure directly over the die locations.  This particular step is about 24.2 mm and lapped to a nice mirror like shine and nicely flat and true for a good contact.

And the OCZ Hydroflow mounting system is very very good.  While other blocks require the sticky back to hold the back plate on, OCZ is utilizing standoffs that are similar to motherboard standoffs to work as a means to hold the back plate very securely in place while you mount the block.  This ensures you won't have problems with the back plate coming loose when removing the block for servicing and may prevent the need to remove the motherboard in those needs.  In addition the thumbscrews are similar to the Apogee GTZ in that you can use the screw heads with your fingers to tighten the screws or switch over to a screwdriver as needed.  More importantly the screws are intended to be installed all the way down until they stop, this ensures that all four corners get the appropriate and consistent amount of mounting pressure.

KUDOS to OCZ for a great mounting mechanism ensuring a good solid and consistent mount for all users!

And last but not least, the OCZ Hydroflow will fit 1/2"ID x 3/4" OD compression fittings with ROOM TO SPARE!!

Flow Rate and Restriction

Along with any water block design comes some amount of restriction, but there is a significant difference in the amount of restriction between blocks.  This is something to consider and be aware of when selecting your pump and other components as it will impact your loops flow rate.  The most scientific and repeatable means to measure and quantify resistance is by measuring the pressure drop across the block inlet and outlet vs. flow rate.  You can then use this information to estimate flow rates of a system and further more it's not specific to any one system setup, so it's usable scientific data.  It's not the easiest to understand, but I'll explain more in a bit.  First up is my tested results using a King Instruments flow rate meter, and Dywer digital manometer, and household tap water to adjust flow rate.

This is a better than average restriction result.

Restriction is roughly the same as the Swiftech Apogee GT, and better than the Fuzion V2, Apogee GTZ, etc.  This is very good and will ensure flexibility in using multiple blocks in the same loop as well as utilizing smaller pump with less heat dump.

Thermal Test Specifications

Rather than repeat and bore you with my testing specifications again, I figured I'd just link you to the detail, you can read them on my Apogee GT review under testing specifications here.  I've followed the same 5 mount method, with the same Q6600 processor, pump, radiator, and sensors logged over 5 hours of testing.

Here is a quick picture of my test setup with some notes on setup

Thermal Test Results

First up is my review of the block tested as shipped straight out of the box with nothing more than installation of the block as most users would make use of it. I utilized the LGA775 back plate and mounting hardware that was included in the package.
Overall testing conditions were held fairly constant thanks to my window A/C unit and logging the results.  Ambient were held on average to 22.1C, water to core deltas were held to 2.4C thanks to the mighty TFC480 radiator, and the average high to low core delta was about 4 degree C.

And to have a look at those results graphically over the range of mounts that I ran, you can see those results here:
Mounting consistence produced results that were within about a .2C standard deviation, and the hottest core ran about 50.7C on average.

Thermal Test Round 1 Compared to the Apogee GT

And for comparison sake, let's take a look at the block compared to some others.

The block is performing equally as good as a "Bowed" apogee GT.  It appears the triangular shaped fins, GTX style corner to corner flow path, and stepped base are adding up to make this block perform equally as well as the well know and now "Bowed" GT.

Recommendations for further Thermal Performance Improvements

After discussion with other testers that have tried this block as well as OCZ and their own testing, it appears there is one area that can potentially produce impovements of up to 2C, and that is mounting pressure.  Because the mounting hardware is separate parts, it is tunable for mounting pressure by simply using more of the provided washers directly under the mounting springs.  I would suggest experiementing with this and see what you get, I have not performed the second level of thermal testing, so all I can provide is what you see above which was with the standard one washer under the spring setup.  Trying two washers could potentially increase mounting pressure to 75lbs, which exceeds the Intel specification, but may yield an improvement in performance.


  • An exemplary accessory package, this ensures that a wide range of users have everything they need to install the block into their systems.
  • Metal Barbs in 3/8" and 1/2" sizes included
  • Low Restriction, while not quite as low as the Fuzion V1, it's very good and very good for multiple block loops or smaller pumps
  • Polished Stainless LGA775 & Universal Hold Down plates minimize footprint (improved MB compatibility) and provide a clean look.
  • Multiple Back-plates included!
  • Delrin (Black Acetal) top, steel hold downs, ensures long term durability
  • Triangular pin matrix is capable of being cleaned by razor blade if needed
  • Stepped Base provides good core contact.
  • Does a find job cooling a Q6600 @ 3.6Ghz, and much much better than air cooling.
  • Low cost - Estimated retail cost is around $40


  • Small packaging box without foam padding
  • Thermal performance while plenty adequate is a couple of degrees behind block performances such as the Fuzion V1. I would suggest increased mounting pressures to further performance.  Of coarse this is beyond Intel specifications, so it should be done so with the understanding of risks involved and performed at your own risk.

Bottom Line

The OCZ Hydroflow water block is a great package in a low restriction design that's great for multiple block loops.  It includes one of the most complete and quality accessory packages I've seen, and has a simple and sleek look.  In addition the mounting mechanism ensures consistent and accurate mounts by all users and prevents the possibility of installing the block wrong.  It's an extremely nice block that keeps my Q6600 @ 3.6Ghz and 1.47Vcore at under 51C under load at 21C ambient, this is something my air cooling just could not do and it provide thermal performances roughly the same as the Apogee GT.  Furthermore, it appears additional performance may be had by simple increases in mounting pressure.

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