I had a scare last night. As I was goin to bed (for once, before 2am, because of a final exam today) I glanced at the fill tube in my closed loop system, and noticed the water level had dropped a lot.

This is intended just as an addendum to the topic of rigid tubing. We will be running a full fittings article later on. Since I've been asked a few times, though, I just wanted to show briefly a ...