Distance between bulkheads and the overflow box?

[Sailfish]

Hi!

I am just about to glue my first overflow box, and was wondering how much clearance I should leave between the bulkhead flange and the overflow box. Should I leave plenty of room to work in, or should I save space in the DT by placing the overflow box right up against the bulkhead flange?

What are your thoughts about the matter?

P.S. I tried googling this, but didn't find anything.

[xmas_one]

Are you asking how slim (front to back dimension) to make your box? If you are doing a Herbie (guessing from a previous post) you do want to run a strainer on the main intake, this and the ability to remove it for cleaning would dictate the minimum dimensions of the box. You can just run a bare bulkhead for the "emergency" trickle drain. Make sure that your trickle drain is only a short distance lower than the overflow box level to avoid splashing (noisy, salt creep) in the overflow box.

 

http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

[Sailfish]

Are you asking how slim (front to back dimension) to make your box? If you are doing a Herbie (guessing from a previous post) you do want to run a strainer on the main intake, this and the ability to remove it for cleaning would dictate the minimum dimensions of the box. You can just run a bare bulkhead for the "emergency" trickle drain. Make sure that your trickle drain is only a short distance lower than the overflow box level to avoid splashing (noisy, salt creep) in the overflow box.

 

http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

My two drain pipes have two 90 degree elbows each, so the strainers will point down and not cause a problem with space

 

Are there any arguments to have the box bigger then minimum, do you think?

[xmas_one]

Going larger with the overflow box means more water will drain into your sump when the pump is off, usually not a problem unless you have a huge overflow box with a tiny sump. Bigger overflows are more obtrusive/unsightly in my opinion. Also, a larger overflow (longer perimeter of the actual overflow at the surface) will not skim the surface as strong as a smaller one at the same flow rate.

[Sailfish]

Going larger with the overflow box means more water will drain into your sump when the pump is off, usually not a problem unless you have a huge overflow box with a tiny sump. Bigger overflows are more obtrusive/unsightly in my opinion. Also, a larger overflow (longer perimeter of the actual overflow at the surface) will not skim the surface as strong as a smaller one at the same flow rate.

Makes sense, with the only exception being the longer perimeter of the overflow skimming less then a smaller one. A longer perimeter overflow will always outskim the smaller one at the same flow rate, because of the thinner sheath of water flowing over it (= more protein to the sump).

 

I do agree with you about the obtrusiveness of big overflows. I just wanted to air the procedure before I glued the overflow close, only to find out a day later that there is some obvious reason why you would really want 2 inches from the bulkhead to the overflow box or something

 

Thanks for the help!

[xmas_one]

Trust me on the perimeter thing. It's not so much the thickness of the layer, rather the velocity that the box is pulling over/towards the weir. Try it both ways and see what works better.

[Sailfish]

Trust me on the perimeter thing. It's not so much the thickness of the layer, rather the velocity that the box is pulling over/towards the weir. Try it both ways and see what works better.

Probably depends if you want to concentrate dissolved organics, or mechanically remove visible surface particles?