Pump pulling from CPU does it make a difference?

[Erasmus354]

OK, to sum up and to check if i've got everything alright (if I haven't I'm gonna commit suicide, i swear
So, when you choose a pump, the only think that really matters is the flow rate...and the pressure if you would exceed it, otherwise it just doesn't matter at all. The shortest the circuit the better because you reduce pressure drop (as everything in the circuit reduces pressure). And, the other doesn't matter at all cause the flow is constant throughout the loop (BTW, you said that rad after pump is a good idea because doing so the cpu block will get the very coldest water... but now that I think about it, the difference might be totally negligible as the pump would only put about 20W in the water, which is nothing compared to all the other heat other blocks put in...).
Mmmm which means that a D5 is the way to go if you aren't going to put many blocks or they aren't really restrictive and the DDC is better if you are putting plenty of blocks or a hell of a restrictive one. BTW, is there any way to mount a loop (a possible one, not one with 10 blocks) with a D5 in a way that the total pressure drop exceeds the head pressure and so water just doesn't flow? Because if there isn't (or at least not one that you will ever do) I don't see the point about not buying the D5...

No flow rate is not the only thing that matters when choosing a pump. Head pressure is still very important. If you look at pump PQ charts you will notice it is a curve. The pump produces different flow rates at different pressure differentials. In general pumps with higher maximum head pressure will get more flow in a water cooling loop when you factor in the pressure differential.

If you were to graph the pressure vs. flow of all your watercooling components combined and superimpose that on the pump pressure vs. flow chart where the two lines intersect is the flow rate you will get in your loop. The Watercooling estimator spreadsheets show this relationship very well. So you want to chose the pump that has the best flow rate for your components (intersects the pressure vs. flow curve of your components at the highest flow rate).


As for temperature drop from a radiator. A 400Watt loop with 4lpm flow (~1gpm) will have a temperature drop of 1.43 degrees celsius from input to output. And you are correct in pointing out how little heat the pump dumps into the water. In that same loop the 20W heat dump pump would up the water temperature by only ~0.07 C. If you assume 200W cpu and 180W gpu and 20W pump if you were to put the radiator directly AFTER the cpu you are losing ~0.7C in water temperature as opposed to putting the radiator directly before the CPU.



@Martin: Great explanation, you put it much more succinctly than I ever could have.

@Naekuh: o.O never thought I would see the day.