Herbie external overflow box questions

[Levinson]

Hi all, I'm trying to learn as much as I can about the overflow options in preparation for a new setup and I've got some questions I've wanted to ask.

1. Assuming there is an internal overflow weir box, is there any benefit in using an external overflow box for Herbie overflow as opposed to just plumbing 90 degree elbow off the bulkhead (also Herbie)? To my understanding, they both seem to work the same way, with a gate valve attached to the drain pipe placed on the lower side to control the flow and silence the drain. Is there a reason to choose one method over another?
Something like the photo below (the pic has soft plumbing but it can be hard pvc) compared to one of those esshops/fiji cube external overflow boxes with standpipes.

2. The small to medium size esshops/fiji cube external overflow boxes attach to the tank with one large bulkhead to the tank. Are they safe enough with the hole being just one (though large)? Reckon they are worth getting?

3. They don't sell external overflow boxes where I live. I don't know if that's what I want yet but I'm thinking it looks straightforward enough to diy with some acrylic and bulkheads. The thing is part of me is pretty scared since any failure would mean disaster. Especially worried about the bulkhead to the external box connection. Would you think it easy to do?

Cheers

 

[NowGlazeIT]

The overflow box in the back allows you to install standpipes of different heights to achieve redundancy. You can mimic this redundancy if all your bulkheads are staggered so that when one overfills the next one starts taking in water. But it’s more convenient to adjust standpipe height in a over flow box then it is to calculate how high to drill another bulkhead.
I think making a overflow box in the back is easier then the weir box. I wouldn’t make my own (and I love to build) only because I really enjoy the craftsmanship of modular marine’s overflows.

 

[Levinson]

The overflow box in the back allows you to install standpipes of different heights to achieve redundancy. You can mimic this redundancy if all your bulkheads are staggered so that when one overfills the next one starts taking in water. But it’s more convenient to adjust standpipe height in a over flow box then it is to calculate how high to drill another bulkhead.
I think making a overflow box in the back is easier then the weir box. I wouldn’t make my own (and I love to build) only because I really enjoy the craftsmanship of modular marine’s overflows.

Thank you @NowGlazeIT. That makes sense!
If adjustable standpipe height was what we want, would something like this (internal overflow box) also work? Please excuse me for the bad drawing. It's not in scale or anything but hope you get the idea.

 

[NowGlazeIT]

Thank you @NowGlazeIT. That makes sense!
If adjustable standpipe height was what we want, would something like this (internal overflow box) also work? Please excuse me for the bad drawing. It's not in scale or anything but hope you get the idea.

I really can’t say for certain but it looks like it would work fine.

 

[DCR]

One advantage to the external overflow box is that it allows you to minimize the depth of the internal box and take up less space inside the tank. Most of the internal boxes are like 1-1/2" thick or less. That is not possible with all the PVC elbows that are needed if only using an internal box.

 

[homer1475]

One advantage to the external overflow box is that it allows you to minimize the depth of the internal box and take up less space inside the tank. Most of the internal boxes are like 1-1/2" thick or less. That is not possible with all the PVC elbows that are needed if only using an internal box.

I was just going to mention something along these lines.

Usually an internal box is very narrow, and the outer box is for the plumbing. What you showed would work, as long as the box was big enough to accommodate the piping, and quite a bit of water so it did not gurgle. It would be similar to a internal tower style overflow, where the bottom of the tank is drilled.

 

[Levinson]

Thank you @DCR, @homer1475. You are right, now I see its cons. Also, much more water would need to be drained out should the bulkhead needs replacing.
Happy new year to you all.