Me! One year into my first BEAN.
All trial and error here.
I have to adjust it from the basement gate near the bottom of the pipe. It's not bad... you just slowly close the siphon gate until you see a small amount of fluid coming down your second open overflow. You could put in some clear tubing in the basement runs so you can see clearly when the siphon is established. Now that I have the hang of it... I don't have to run up and down stairs to see if I have it right - I can adjust on the first try.
You want the gate as low as possible to avoid noise, bubbling, etc... Basically a solid column of water with minimal room for air intrusion. If you have the lower end submerged so that no air can get it from the bottom... it might work with the valve higher... not sure. If bubbles got back into the pipe it could disrupt the siphon below the gate valve with a noise and splashing.
Since I cannot submerge my pipes (they pour into a roller matt), I did not try the totally submerged method. I did find that I needed to vent the main siphon tube below the gate to make the water come out smoothly onto my rollermat to avoid splashing and foaming. Splashing and foaming is bad because it prematurely trips the rollermat float valves and eats up media. But, my setup is a bit more complex yet... since the water gets divided between two rollermats and a third overflow directly into the sump. Venting might not be necessary in your case.
Here is an idea... put a gate valve in both positions and try submerging the siphon in your sump. If the top gate fails to work... (like mine did) no biggie... just leave it open and use the bottom one. Also, experiment with dry fit and teflon tape until it works the way you want it.
