Regulating pump speed - good, bad or just not important?

Alright, fellas - I got a question for the hardcore water cooling guys out there.

I've been doing quite a lot of reading (for instance, see this: http://www.xtremesystems.org/forums/...d.php?t=234698) about regulating pump speed. Usually, the main argument is that the pump would stop producing so much noise when there's no need for a high flow. Which, I guess, is a valid argument.

But then a friend of mine told me that when testing an old D5 (not the vario - the older one) he actually experienced that running that pump at a high speed, the resistance in the water loop would heat up the water - not just by a few degrees, but quite radically.

So, I was wondering if there isn't a certain balance - a certain flowrate - where the speed vs. cooling ratio is the most efficient.

Any of you guys done any research into that field?

min flow rate you want is 1GPM, ideallly 1.5GPM and anything above 2 GPM is pointless for most blocks, some restrictive ones, like the cpu 350 from koolance, like more flow.


i wouldn't bother worrying about changing the speed of the pump personally, but thats up to you.

and + rep for the link as i just learned i could put a tach wire on my 655 vario!

Sure, I've got switch mods on my DDC3.x pumps, so they can go from being 9w to 18w at the flick of a switch. Thought about putting pots on them. That's just being silly.