water level dropping?

[hell167]

I've had my system up and running for about a year now. And it seems to me that the water levels in my reservoir has dropped about 1mm since I had topped it off about a year ago when i built this system. Is this normal? I've opened up the case yesterday and there doesn't seem to be any leaks, no wet spots no discoloration, nothing i can see. Looks to me that everything is running normally.

[SoulsCollective]

Yes, that's perfectly normal. Tubing is slightly porous, and so some of your coolant will evaporate away through it - it's nothing to be concerned about, as the rate of coolant loss is extremely low and coolant is lost vapour rather than as water droplets which might cause shorts.

[Red M]

It's perfectly normal, it's due to the little things like air bubbles in the water, very small 'leaks' (I use that word loosely) at the seals and plastic absorption from the tubing, much like when you blow up a balloon and over the course of a couple of days it deflates.

I use a tee join with some 1/2" tube ruining off it as a bleed line (reservoir) and the water level noticeably drops over the course of a year even though there are no perceivable leaks.

Edit: Oops beaten to the punch line, pretty much what soul said ^^