[V12|V12]

Well, I found a supplier for great hollow acrylic cylinders, Tap Plastics. Now I need to dust off my rusty copper soldering skills and make this thing.

Where is this place, and how much are they, by size etc...?

I guess my question is, why the need for an airtrap.

Well, You don't have to have a Res/Trap, but as time+heat+cooling of water+Turbulence of the pump etc... there WILL be air-bubbles that will form or be released from the water and as micro-sized as they start out, they aren't really noticeable during the first while of running, but when ever you turn off the power and the water stops flowing, then they will start to settle and collect, and since you have no way to actively trap them, they will only continue to increase... and that means you'll have to go through the hassle (if it is to you) of adding more water. And here's a BIG problem I see; Any time you have to add water or mess around with the system, your putting some part of your compents at risk. You, myself and anyone else, may indeed be as careful as possible, but there is ALWAYS a chance that a SMALL, undetected droplet has splashed it's way on to a vital connection, etc... and then Poof... But hey, everyone likes playing the chance game