me, too. I don't adjust the gate valve too much, either. Seems like when the tank was new, I was adjusting it every few days. Don't if the pipes were too new, or I just didn't know what I was doing....or both. But it's settled down now for sure.
Im confused isnt that more of a bean animal set up ?Yes, I have only 1 return submersed return pump running.
I have the Herbie style with straight stand pipes - so only 1 fully siphoned drain. The second is a trickle. I also have a third, completely dry standby. I run the PVC for the third so the output/spout ends above my return pump chamber water level to "splash" if it's ever in use (i.e. my other pipes start to become clogged).
If overflow space was not an issue for me, I'd would have gone with 1.5" (not larger) if I could have. But I don't think I've compromised much to have a dry standby. I do know that folks running the Herbie end up closing their full siphon drains (with a gate valve) at least half way or more anyway. This is to help achieve the siphon and set the level for the second trickle pipe.