[John Rogers]

What I was referring to was the system "appears closed" but in reality is not, i.e. air can get sucked in but water cannot get out. Since water molecules are a tad larger than air they cannot get out. We used to see this in steam condensers and finally the Navy used air to do leak tests instead of water in their main condensers. Sammy and some others may verify this although the Navy only has a few ships with "condensers" now-days!

I think turning off the power and cycling it to flush out the existing water a few times is a good test and if the bubbles disappear then you know the problem.