@mercyless well.. it's complicated.. is all that hardware that got accumulated overtime and, I decided to put to use this weekend..
7800x3d + 7900xtx (450w) + 4 screens that pump a lot of heat to the room which does not have good air circulation..
The actual setup with 2xD5 + cheap barrow + 2x1260mm + 4x360mm gives me about 135l/h on 100% - to avoid having thermals climbing up I need to keep the pumps at 80% (120l/p)..
Any less than that thermals will slowly go up.
It is a very restrictive setup with gpu + cpu + ram blocks, plus few QDCs (7 to 9, not sure), even more 90 angle fittings, 2x1260mm and a stack of 4x360mm rads.
If I run the above with 2xD5 + barrow at around 65% (100l/h) thermals start to climb up slowly. If I run it about 90% (120l/h) thermals decrease to a very comfortable level, therefore the need of a fourth pump. I could however sell all 4x360mm rads with the fans and all, but I already have all that here dusting up so I've put it to use.
edit
chatgpt is scary.
I've asked about having the four pumps in the same header as long as I'm using just the "tach" and "pwm" wires. It went a bit further and reminded me that I just actually need 1 "tach" wire, which is useful because I'm crimping the cables myself. It gave a whole sensible answer that I'm perplexed.
Then I described well the loop and it's parts, plus a ball-park of 45/90 angled fittings and the mot****er said
four d5 pumps and that three D5 pumps could potentially suffice, mentioning a
Overkill Factor.
Anyhow, I will split the fans in pairs of headers, it's safer, just more work crimping, sleeving...