Are you sure the 3/4 eached Full siphon ?
Can you post pics of the plumbing and stand pipes ?
If the pipes height are as shown in the first picture, the taller 3/4" pipe may not reach full siphon being a few inches under the water level.
OP, I would add strainers to your siphon standpipes. It's worth it IMO.
I cut down the second 3/4” drain to make both full siphons. It’ll flow real well but I think I’m being limited by the overflow teeth. It’s a side overflow box. When I cranked the pump up and tried to tube it the main tank level was high. Does that make sense?
Looks great!View attachment 1308574 View attachment 1308575 View attachment 1308576 View attachment 1308577
Her are some pictures of how the drains are set up on my tank. The H2Overflows are both full siphon and the low profile strainer is the emergency drain. All are 1.5” drains.
Sorry for the delay. Here’s some pics. I’ll try and get a video.
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