Should a WC loop "use" water

[G-Dubs]

I've just started using my first WC set up and I'd swear that the water level in the res is going down slightly although i'm not convinced i'm not imagining it.

I have checked for leaks again and again and all is bone dry.

I notice condensation forms on the inside of the res, although the temps are good.

Do water cooling systems lose a very small amount of water to the atmosphere this way?

Basically is this normal?

 

[G-Dubs]

Thanks for the reassurance guys. i think it's probably the bleeding thing. I've been using it for about a week now and at first was hearing quite a bit of gurgling every now and then, which has now largely subsided.

I did have the top of the res loosely closed, as I was worried about building pressure in the system, but now have it closed off with a plug.

I now have lovely clear bubble free water

 

[G-Dubs]

If it continues to drop, just fill it up a bit, but if it keeps going down, then that might be a problem.

Problem as in leak? or other problem?

Is it best to keep the top of the res screwed down or just loose to give a bit of room to breath?