[Brians256]

HVAC tubing is impermeable. That's about it. Nothing else really needs flexible impermeable tubing. Hehe, odd that I actually know about this. But, most other applications need either impermeable or flex but not both.

If you want cheap and impermeable, give up flex and use copper tubing.

I already knew about the issues that Bill mentions, which is one of the reasons I have a huge res in both of those system. I thought it was common knowledge. That is one of the reasons why I'm not happy with the bay res used by both DD and Swiftech: it needs to be refilled too often. I was adding more coolant every month or two, and that's just too much work for me. I turned off that system and will restart it when I have a larger res. Plus, that res is hard to keep silent, since it is horizontal. In order to prevent splashing, it has to be kept almost totally full; even minor decreases in fluid volume cause it to splash, foam and gurgle.