Question I have to low water flow, and don't understand where the problem is


Aug 8, 2012
I have a Mo-Ra3 external radiator with a reservoir (Bitspower 200) directly connected to the top outlet, and an Aquacomputer mps delta 40 attached at the bottom of the tank, checking the level. It goes to 2 pumps in series (ca 1 meter tube, 2 x Aquastream Ultima). Up to a block on the Aquaero 6XT. Then horizontally for 25 cm to an Aquacomputer mps Flow 100. Into the MosFet cooler on a Maximus X Formula. Into an Aquacomputer Vision CPU block. Into 2 Asus Poseidon GTX 1080 ti in series (not parallel), And back to the radiator. The height difference of the system is about 50 cm. The total length of the tubing is about 3 meters.

I have checked the CPU block for clogging, it's clean. The Poseidon cards shouldn't be able to get any clogging, as it's just a tube running through in a U, and it's behind the CPU block anyway, so any clogging would be there. The block on the Aquaero is totally open, just a short U. The flow mps is brand new (bought a new one, just in case). A visual inspection also shows that the meter is probably correct.

If I close the reservoir (membrane plug that should equalize the pressure, so the level meter works correctly), the level value increases rapidly, probably showing a pressure building up (I can actually hear the pressure being released when I unscrew the membrane plug). To me this indicates a serious clogging somewhere, but I'm unable to understand where it can be. There's no leakage in the system.

At 3500 rpm the 2 pumps manage around 20 l/h (too low for the flow meter to measure accurately). At 5000 rpm they manage around 42 l/h. This should be at least doubled, probably tripled, in a normal system (I've had these types of pumps since 2012). The values vary +/- 3 l/h at 5000 rpm and closer to +/- 10 l/h at 3500 rpm, but they should be fairly stable.

Anyone got any ideas? The only thing I can think of is the radiator, but I don't want to start with that mess if I don't have to.


Contributing Writer
Staff member
Can you provide a picture?

I'm thinking you have more restriction than you might think, causing an issue, but you also could be fighting a decent air pocket. Full-cover GPUs in series can be restrictive, which is why most people run those in parallel.

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