I though it will be worthwhile to share in a separate thread my observations of flow with 2xD5 vs 2xDDC (both with EK tops, serial), perhaps someone will find it useful (or not )

On system - let's call it "A" (see my worklog for details), with 2xD5 with EK top I was getting 200l/h.

With the following changes:
Change from MCR200 to RX360 (less restriction)
Change from serial GPU to parallel GPU (less restriction)
Change from 2xD5 EK top to 2xDDC EK top (3.25 - branded as Koolance PMP-400)

, flow is 205l/h

With the 1 pump on, 1 pump off the D5 did 130l/h while DDC does 160l/h.

So my 2 obvious observations are:

1) D5s scale much better in series - as 2xDDCs are not better for long loop than 2xD5s (and in fact they might be a bit worse if you account more than 5l/h improvement to the rad swap & parallel GPU)

2) 1 DDC is indeed better for long loop than D5 but it does make sense to add 2nd pump for redundancy/flow - so see (1)


Please note there are no scientific methods to the above - except for the flow meter observations - nor it is any testing - it is just observations of 2 specific scenarios on my system which may benefit other in similar situation.