BB, well actually with my planned design, you don't
HAVE to have the PVC tube that large, it could be 1-1/2x2,3,4 etc... or 2", just as long as it holds a decent amount of water. The way I perceive the design to be is a 2 part; 1-part PASSIVE airtrap, and 1-part ACTIVE Resevior. Also, if space is a factor, which it usually is, unless you're a full-tower junky

there are MANY control factors to how active/passive you want it:
1) Res size will determine just how much turbulence buffering you'll have and amount of available water for system.
2) "T-splitter" size will determine just how passive/active your air-trap portion will function, it will also be a turbulence control factor (larger = more efficient at releasing air and less turbulence/velocity of incoming water)
3) The little plastic-slit could be adjusted (working on a way how to NOT glue it, but have it held securely) to also control for the actual amount or % of incoming water+air that will flow up into the Res part itself.
Damn it, the Fashion bug has hit me... I used to be TOTALLY in to function over form, but now, I just love me some CLEAR plexi/lucite to show off the goods (mainly glowing UV dye in water, ha!) So I need to find a local place that carries nice size clear PVC and such. Ordering online is too much $$/ft....
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XP 1600+ AGOIA-Y (GreenLabel, UNLOCKED!@/ NF7-S 2.0/ PC 2700 DDR
10.5*172FSB(1806/ 1991 high), Vcore 1.792...@84.95Watts
--86' Chevette Heater Core
--1/2" Vinyl tubes
--Via1300-Stealth Mod(QUIET!)

---Home made copper-tube block
---PVC small internal res