Clarification on BeanAnimal overflow

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Hi all,

I've been reading through the BeanAnimal thread and his website but there's a few things I'm confused about.
But before I get to that this is what I gather. Please tell me if there is a problem.

1. 3x 1" bulkheads.
2. Coast to coast overflow, without teeth.
3. Return comes over the aquarium and terminates under the water line.
4. All bulkheads are horizontally level (i.e no need to have the siphon line bellow the others).
5. It's better to have ball valve on the siphon closer to the sump end rather than the bulkhead.
6. Distance between the down turned elbow to the bottom of the overflow can be about ~1/4. You can have the downturn elbows touch to the bottom of the overflow if there are teeth cut in to the 90 elbows. As I understand this is better way to keep animals from going in to the drain pipes.
7. The height of the emergency pipe determines when the emergency drain kicks in.

What I'm confused about is,
1. What's the minimum distance between bulkheads/ drain hole centers (horizontally)?
2. What should be the distance from the top of the glass to the centre line of the drill hole (1" bulkhead)? I read somewhere that there needs to be a 1" drop from the overflow to the drain pipes.
3. What's the distance from the bottom of the aquarium trim to the top of the overflow? Should the overflow height be set to the bottom of the aquarium trim so that the water line is invisible?

I get the concept of the BeanAnimal overflow. I'm just not clear as to how determine the other things. I've never constructed an overflow before.
Any help is greatly appreciated.

 

[SGT_York]

5. I don't agree with, better to have a gate than a ball regardless of any other factor. And the system works fine with the valve up top but does work down below if needed to.

6. just make sure the teeth are large enough so they don't restrict flow. It is much better if you protect the entire overflow with a lid (some type of screen to keep things out of the overflow itself not just the pipes)

7. Yes, just make sure it is low enough to handle the flow without overflowing the tank. It will take an inch or more to create enough pressure to handle the volume. So don't make it as tall as possible.

Minimum distance I like to drill is 2x the hole size so for 1" bulkheads it's about 3 inches (holes diameter is key not bulkhead size)

1" drop is good, any more and you will get sound, any less and you could get air sucked into the siphon.

3 is right on, hide the waterline.

Enjoy you won't regret you did it this way.

 

[syntax_error]

Thank you for your reply SGT_York.
How far down should the holes be drilled? i.e The distance from the bottom of the aquarium trim to the center of the hole? I've read 3.75" and 4". Is that correct or too deep?
Also, the trim is about an inch deep. If the top of the overflow is set to the bottom of the trim is there a possibility that water will spill out of the tank? (Maybe when the siphon is starting, or the wave action of a wavemaker).

(Aquarium is a 40g high. 36" x 13" x 20").

 

[NanoReefWanabe]

the holes centre should be a minimum of 2hole diameters from the edge…1" bulkhead typically requires a 1.75" hole…so minimum 3.5" top edge of glass to centre of hole…

things to note…

first, the top of the glass is not at the top of the trim, rather it is about 1/2" lower. so from the top of the trim to the centre of the hole should be a minimum of 4"

second, you will need to measure the the height of a 1" 90* elbow from the centre…if i remember it is about 1.25"…this number is crucial to determining the the top and bottom of the overflow box and hole location of the main bulkheads. (hole centre 4" down will put top of up turned elbow 2.75" below top of tank which should leave plenty of room for surge and power down refill, it also means the bottom of the down turned elbow will be about 5.25" so the bottom of the box will have to be about 5.5 to 6" from the top of the tank. a typical tank trim is about 1.25" so this means the minimum you box can be is 4.75" tall) that all seems a bit tight to me, i would lay it out and double check for yourself..you want a good 4" of water over the bottom of the down turned elbow to prevent siphoning air...

third, you want to maintain a minimum of 1" drop of water into your box, or you won't get proper surface skimming.