Beananimal/ Herbie Hybrid Observation - Help?

[justincgdick]

So I have a Beananimal on my 165 but... I set mine up like a Herbie. One drain is fully submerged about 1/3 of the way from the top of the OF, another open standpipe at the waterline you wish to maintain, and the third open at the MAX ever water line. I just had to test that the open standpipes will handle the entire flow if it ever gets to that point. It handled it no problem so I can't see the reason for the sanitary tees, air line, and the "flush" feature.

I'm also not sure how it happens, but my system finds this balance where the main drain is full syphon and the water ISN'T trickling down the open standpipe. It just floats in between... meaning it's a perfect balance. I thought the water would eventually drop the the level of the main drain, or increase and begin to trickle down the open pipe, but it hasn't in days.

Can anyone explain how this happens to me? I would assume I managed to find a perfect balance, but it seems there are other forces at hand. It's too easy to set it, and I can adjust my gate valve a smidge and it will re set to the same point. Is there some sort of force and effect here where the gravity and water work together to reach this equilibrium? I know it sounds odd, but I've got a darn good understanding of water dynamics, overflows, etc., but finding this balance by fluke after messing with my system doesn't seem likely.