Bean animal overflow help

[mwbeach]

Bean animal overflow help please. I have a 151 gallon, this is what came with the tank, I’m unsure if manufacturer or if store made them. Three drain lines in overflow. The emergency is cut and dry. The other two are exactly the same with 3 holes drilled in the top and maybe 1/8” difference in height. I am by no means an expert, but doesn’t seem right to me. Can anyone help me understand this better?

 

[don_chuwish]

The holes drilled are fine. But make the primary full siphon drain MUCH lower than the secondary. As low as possible.
Then the secondary should be just a little lower than the emergency - but high enough that the overflow box water level is as high as the top of the bulkheads coming from the tank. Make sense?

 

[MarshallB]

It should still work. Only the secondary needs a siphon break hole, preferably on the top. Not sure why there is one on the side or why the primary has a siphon break. Either way you should aim for 1/4-1/2 inch clearance between the bottom of the overflow box and the start of the primary drain. Give the size of that hole on the secondary you will probably need it to be around 1/4 inch below the emergency drain or else it will continue to suck in air and never create a siphon ( Which is important if the primary drain ever clogged ). Start off tall and lower the height till you find what works.

If it doesn't work just make 2 new ones. You only need a small hole on the top of the secondary. 1/16th-1/8th. Ideally once the main drain is at full siphon the water level should be just below the siphon break hole on the secondary.