What happens if you use reverse flow in contrast to the ideal flow path?

By swapping the ideal setup for the “in” and “out” ports on the GPU water block, the liquid path is reversed, which is why it’s called “reverse flow”. The coolant will first pass over the RAM and VRM section and then enter the fin stack from the sides. When the water block is filled up, the liquid meets up at the middle of the fin stack and exits through the jet plate and flows to the terminal. Sounds totally wrong, but actually, it doesn’t make much of difference.

Performance and testing

Through EK’s internal testing, we can assure you that the difference in cooling performance while using the reverse flow in GPU water blocks is insignificant. The performance test was run 5 times consecutively and the average of the flow rate and GPU core temperature was recorded.

Using a D5 pump on our test setup, the coolant flow rates are actually the same. 238 L/h in the ideal setup in reference to 240 L/h with the reverse flow. We can easily say that the volumetric flow rate is the same in both scenarios and the small difference recorded is only due to the margin of error while testing.

The temperature difference recorded on the GPU core while using the EK-Vector RTX 2080 Ti water block in ideal versus the reverse flow path scenarios is… drum roll… 1.5°C. Yes, only 1.5°C. Of course, this it can vary a bit depending on which card you own, the voltage it runs on, if its overclocked, what is its BIOS power limit etc. But in general, you can expect an average of less than 2°C worse performance when running reverse flow, compared to the ideal flow setup.