How to plumb my particular tank to my sump?

[Seno2k]

I'm having trouble figuring out how my 125 gallon acrylic tank was designed to be connected to a sump. I've attached a diagram of my tank so people have a sense of how it's designed.

Basically, the tank has what I think are two separate overflow boxes, each of which has a single hole drilled into the bottom. The holes in these overflow boxes are the same size. Meanwhile, the top of the tank has two slightly smaller holes drilled into the top, just off to the side of each overflow box. In the middle of the overflow boxes is a single shaft that doesn't have a bottom in it.

Unfortunately, my research on how to setup the tank has struck out. I've just not able to come across any examples of tanks that look like mine. My best guess is that the holes at the bottom of each overflow box are drain holes and that the slightly smaller holes at the top of the tank are meant for returns. I suspect that my tank is designed to utilize a Herbie Overflow system whereby the drain hole in the first overflow box would house a primary standpipe with a strainer attached to the end of it and the second overflow box would house an emergency standpipe that rises up just below the weir. Then two return pipes would run up through the middle bottomless shaft that sits between the two overflow boxes, up over the tank, and down into the tank through the two slightly smaller holes at the top of the tank.

While this all seems well and good in theory, I have no idea whether it would actually work or not, let alone whether it's actually the setup my tank was designed for. If someone who has experience in this area could weigh in I'd be very grateful.

Drawing of My Tank

 

[Soren]

I don't have any experience with a tank like yours, nor do I have much experience in general other than reading/research.

It sounds to me that you got it right, though I don't know for sure about using the drains for different purposes rather than just making both regular drains with strainers. Ideally, there would be more than one bulkhead in each weir for different-purpose drain pipes.

The small holes next to the weirs are for the return lines, like you mentioned.

Hopefully others with more experience can help you out more.

 

[blaxsun]

I took a look at your diagram (very helpful, btw), and I think your assessment on how it was configured is bang-on. I assume the top is a removable U-shaped lid with the slit in front, the two small holes and a cutout for both weirs and that center bulkhead between them?

I think the herbie setup you outlined (1 standard, 1 emergency) is probably your best bet. The only change I would make would be to drill a single hole in the bulkhead between the weirs for a return outlet, design it for at least 3/4" plumbing and run a Y-shaped spit nozzle on the return outlet. Then you can remove the lid entirely and go with a mesh lid.

I'm also not an expert, but based on my own tank configuration and plumbing I think you've got a good handle on it from where I sit. Good luck!