Watercooling system losing water mysteriously

[Rav]

I have a closed system with the following componets:
DD Block, Cube, Danner 7
There is no resivoir, but I do have an expansion tube at the top. Lately I've been noticing after a good day's use the water level drops an inch or more (4 inches after a LAN party!). I don't see any leakage anywhere, and the end of the expansion tube has a rubber cork in it. I heard once the Danner can let air in, but I can't find any water coming out of it. Could enough water actually vaporize and get out? The water gets warm but not hot. I also don't think this much air could have been trapped in the system, unless there was a TON dissolved.

Anyway, is this a problem or does this normally happen? Any fixes/suggestions? Thanks everyone.

-Rav

 

[Thelemac]

That just shows that there's still air in the system. Eventually it will all be bled out, as long as you keep filling the expansion tube.

 

[cjtune]

Water will always have air dissolved in it, just like all the other dissolved gasses and minerals. I think you can bleed most of the air out but if there's only a bit left, the warm water should be able to absorb it. By absorbing some air pockets beyond your sight, the water will occupy it and may appear to have evaporated and escaped from your rig. Try and see whether the water level rises and drops periodically (ie. in cycles). BTW, water CAN leak from your rig but it'll be invisible (and be very little). No seal or stuffing on this planet is completely water-tight.