Chest tube ?: Sxn vs water seal

So I felt pretty comfortable with chest tubes, then yesterday we were having a discussion at work and now I'm confused again!

I've always thought that bubbling in the water seal chamber is indicative of an air leak, and that tidaling with respirations was good because it indicated the lung was re-expanding.

Now several of my coworkers stated that when the chest tube drainage system is to suction, the above it correct. But when to water seal, then tidaling means an air leak. I never thought there was any difference except that in air leak obviously you won't have bubbling in the suction control chamber.

Help?

Thank you!