Bean overflow levels?

[Oceandreamadean]

Hi, I'm going for the Bean Overflow set up on my reef tank & am looking for some advise on the plumbing. I have the external weir/overflow box with (x3) 1 1/2" bulkheads. My external weir also has combs for the water to skim over.
I have seen the B/O with T's and and elbow turned down on the full & partial syphon with an upturned elbow on the emergency pipe - but I have also seen just elbows turned down & up for the emergency. What's the advantage of using a T piece with a 90deg elbow as oppose to just using a 90deg elbow turned over?
Also should (regardless of T piece & 90 or just 90), are the full syphon pipe & partial syphon pipe plumbed in at the same level - or is the full syphon set a little lower? I know the emergency pipe is of course higher but can never make out from photos whether the two syphon pipes are plumbed at the same level or not.
Also what level above/below the combs should the pipes be & by what measurements please. Excuse so many questions but I'm a complete newbie :spin2:

 

[Mrramsey]

On a regular ba overflow the tee provides access for a clean out plus the airline for the trickle drain.

 

[Mike Ordner]

The bean animal on my tank is different than what is recommended. I have the full siphon pointed down, but I have the partial siphon and the emergency pipe pointed up. My thinking is the partial siphon is at the water level and gives me one more shot at skimming the water as it pulls over the edge of the pipe. It is still silent as the water sticks to the inside edge of the partial siphon pipe. The emergency is about 1/4 inch higher so it stays dry unless something really bad happens.

 

[RocketEngineer]

Honestly, I would get rid of the combs as they reduce surface skimming which is the whole point of an overflow.

Second, there is no "partial siphon" it is a Durso. You either have a siphon or you don't, there is no third option.

I also have an external box. In my case the bulkheads are in the bottom of the box and there are three stand pipes inside the box. Because the standpipes aren't glued into the bulkheads I was able to play with mine a little more than others. My siphon stand pipe has two elbows, my Durso has the elbow turned down before the tee, and my emergency has the elbow turned up before the tee. The top of my siphon standpipe sits about where the bottom of the inlet on the Durso tee is. I found this works best for my situation on the restart as the siphon clears a lot faster in this configuration. Your results may vary so I recommend playing with it before settling on a final configuration.

 

[Fishmommy]

I have my full siphon just a straight pipe pointing up.
My trickle drain is a t pointing sideways and up. The sideways part is where the water trickles in.
My emergency (3rd) drain is just a straight pipe pointing up.