Liquid Flow Restriction

To make things simpler, I have decided to use a CORSAIR Hydro XD5 pump/reservoir combo unit rather than a discrete pump and reservoir. The pump is powered by a direct SATA connection to a CORSAIR HX750 PSU and controlled by an Aquacomputer Aquaero 6 XT. There is a previously calibrated in-line flow meter and Dwyer 490 Series 1 wet-wet manometer to measure the pressure drop of the component being tested—in this case that of each radiator. Every component is connected to the manometer by the way of 13/16 mm tubing, compression fittings, and two T-fittings.


As of the time of this review, I have tested six entries in total. Unless specifically mentioned, every one of them was tested with an accompanying backplate. As that is the majority of them at this time, this will not change in the near future and was done because both Alphacool and CORSAIR include a backplate. All six will have dedicated reviews, and at least three more from other vendors are being tested now. So keep in mind that the highlighted entry is for the CORSAIR Hydro XG7 block and backplate combination.

Of course, I would say that a backplate generally does not matter as far as liquid-flow restriction goes, but this generation has been nuts. Not only have we had some very interesting water blocks come out for the NVIDIA Founders Edition cards, but the hot VRAM on the back of the RTX 3090 PCB has caused enough interest for a couple of companies to offer active backplates for the first time. This is why there is a separate entry wherever an active backplate is added.

So here we are then, and we see that the modular CORSAIR design with the skivved GPU core section ends up the most restrictive of the lot. This is mostly because of the many more fins and smaller channels compared to the others, with the series coolant flow path adding slightly to this. It is not that far off some of the others, but about 50% more restrictive than the least restrictive block tested thus far.