Flow test of various waterblock designs – Joe
SUMMARY: Maximizing waterblock flow rates requires large, unrestricted openings.
I tested a number of different waterblock designs for flow rates and thought the results were interesting.
For this series of tests, I used the following waterblocks:
| Waterblock | Intake Diameter | Type |
| AquaJoe | 3/8″ | Pins |
| Asetek | 1/4″ | Half Moon |
| BeCooling Open¹ | 9/32″ | Open |
| BeCooling SlitEdge | 3/8″ | Slit |
| Comserver | 3/16″ | Spiral |
| Cooling King | 3/8″ | Pins |
¹The BeCooling Open is a block that’s 2 1/2 years old – I included it to see how things have changed over time.
The Intake Diameters listed are NOT tubing sizes – these are measurements I took of the narrowest opening of the intake nipples; for example, while Comserver’s slip fittings are for 3/8″ tubing, it narrows down to 3/16″ at its base. This is an important distinction as it directly impacts flow rates.
To measure flow rates, I used an Eheim 1250 waterpump (rated at 317 gph) hooked up to a King Flowmeter. I used the Eheim for flow rates of 1.75 and 1 gpm as more typical of watercooling systems, and then a Little Giant waterpump, #3E-12NYS (rated at 500 gph) for the 3.0 gpm test series. The little giant is noisy and large, but a good example of an “extreme” waterpump.
Included in this setup is a valve to control flow rates, so I was able to vary flow rates to 3.00, 1.75 and 1.0 gpm. During the test, the only change made was hooking up each waterblock into the test rig for each pump. The Freeflow rate was measured without any waterblock in the test loop.
| Waterblock | Flowrate gpm | % of Freeflow | Flowrate gpm | % of Freeflow | Flowrate gpm | % of Freeflow |
| FreeFlow | 3.00 | 100% | 1.75 | 100% | 1.00 | 100% |
| Be Cooling SlitEdge | 2.79 | 93% | 1.60 | 91% | 0.97 | 97% |
| Cooling King | 2.64 | 85% | 1.48 | 88% | 0.94 | 94% |
| Asetek | 2.41 | 80% | 1.31 | 75% | 0.88 | 88% |
| AquaJoe | 2.22 | 74% | 1.18 | 67% | 0.83 | 83% |
| Be Cooling Open | 1.80 | 60% | 0.90 | 51% | 0.70 | 70% |
| Comserver | 1.46 | 49% | 0.77 | 44% | 0.62 | 62% |
Predictably, narrow openings yield lower flow rates, as the Be Cooling Open and Comserver waterblocks show. In addition, narrow openings combined with a flow restricting design takes a large toll on flow rates, as the Comserver spiral design clearly shows. However, designs that feature large openings, even with pin fin designs, are more flow-friendly overall than others.
Minimizing waterflow resistance in watercooling systems is an important factor affecting performance, all other things being equal. Many newer designs sporting 3/8″ openings are clearly less resistive than others, although interior designs (pins, spirals, etc) have a significant impact on system resistance as well.
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