The German web shop Aquatuning (http://www.aquatuning.de), specialised in water cooling for computers, state in their guidelines for water cooling (http://www.aquatuning.de/product_info.php/info/p342_Aquatuning-Tipp--CPU-und-Wassertemperaturen-.html):Aquatuning Anweisung: ... die Wassertemperatur sollte 35°C nicht überschreiten, da dann die Lebensdauer der Pumpe herabgesetzt wird. Beachten Sie diesbezüglich die Pumpenanleitungen der jeweiligen Hersteller. Schäden, besonders an der Pumpe, die durch überhöhte Temperatur entstehen, fallen nicht unter die 2Jährige Produktgarantie.My quick translation:
"The water temperature must not exceed 35°C, or the [expected] life span of the pump will be shortened. Take note of the manual provided by the manufacturer. Damages caused by over-temperatures are not covered by the two year product warranty."

So, is this an issue? It seems reasonable that pumps designed for use with aquariums are opted for water temps <30°C and not required to survive much higher temps. What about the pumps designed directly for computer water cooling? And what are the typical water temperatures?

I noticed some years ago that Asetek rated the cooling capacity of their radiators based on a water temperature of 40°C. For their systems they used Hydor (aquarium) pumps, and recommended the radiator to be placed immediately after the pump in the loop, meaning that the pump would be exposed to the warmest water possible!

Comments?

Cheers
Olle