overflow weir size?

[Lorretto]

I have 14 gallon tank. what size dimensions would my overflow weir have to be?


I was not going to drill my tank and risk breaking it so I'm have to make a weir. To do so I need a proper size so it work.

[fuzzyt]

Have you considered buying an overflow box with a standard u-tube? I'm not sure how small you can get them, but it might be easier and more cost effective than building a weir. Just a thought.

Best of luck! :)

[coralfragger101]

Your weir size would depend on how much flow you want to go through it. Any idea?

[Lorretto]

overflow box is too pricey. I now have the tool to make my own and it's much cheapers to DIY. I guess I'll have to ake a couple and see which one works better.

[abelh7]

sorry to but in here but since yall are talking about overflow boxes. i was going to drill my tank but it is oceanic and i dont want to risk it either. what kinda problems could you have using an overflow siphon breaking etc.....?

[Just195]

i am also interested

[RandyStacyE]

I don't believe it is the size of the inner overflow box that has anything to do with it. The diameter of the U tube does help to reduce the possibility of trapped air, but that can easily be worked out by making a few to figure out which works best. Like coralfragger101 said, it depends on how much flow you will be putting through the display tank.

The principal of a siphon overflow is very simple, but minor alterations do make a big difference. If this is your first overflow, it’s probably best for you to just buy one. I’m all for a good DIY and more power to you if you get it right on your 1st try (2nd alteration or your 3rd). Here’s one I made, but I highly doubt it would help you with yours.
http://www.randystacye.com/diy_overflow.htm

[coralfragger101]

I'd have to disagree with the size of the box doesn't have anything to do with it.

The majority of premade overflows will run about 600 gph through them. Using a calculator this will require a 9 inch linear overlfow. This means that if you want to run 600 gph through your overflow box then that box would have to have a minimum circumference of 9 inches. More if you add teeth. So the size of the box actually has everything to do with it.

[Keelay]

<a href=showthread.php?s=&postid=9977182#post9977182 target=_blank>Originally posted</a> by coralfragger101
I'd have to disagree with the size of the box doesn't have anything to do with it.

The majority of premade overflows will run about 600 gph through them. Using a calculator this will require a 9 inch linear overlfow. This means that if you want to run 600 gph through your overflow box then that box would have to have a minimum circumference of 9 inches. More if you add teeth. So the size of the box actually has everything to do with it.

What calculator did you use? If you have 600 GPH running over a linear overflow you'll have a fixed height of water over the rim or fixed height of teeth used. If you kick up your pump to 1200 GPH you'll have exactly twice that height of water going over the rim or through the teeth.

The water will enter the box just fine no matter how fast your pump is flowing. The limitation is, as Randy said, in the diameter of the U-Tube. that small channel of water will only support so much flow.

[RandyStacyE]

Another factor is the amount of 'fall' or the difference in height from the inner and outer overflow compartment.

Check out the Lifereef overflows. You'll find that their overflows are built with a much better design than their competitors. Their exterior overflow compartments are much deeper, their stand pipe is set lower then anyone’s and they also have a baffled compartment to aid with a deeper compartment and prevent problems due to power loss.

The additional depth in the exterior overflow compartment allows their overflows to make better use of the U tube allowing it to be rated for higher flow (farther the drop = more flow). Higher flow also discourages air from accumulating.
http://www.lifereef.com/siphon.html

coralfragger101, I’m sure you are right … there’s likely an ‘ideal’ lineal inch of overflow circumference which would allow for better surface skimming and would optimize an overflows’ performance. I was just pointing out that the ‘majority’ of the most critical issues with constructing a nice overflow is determined by the actual ‘siphon’ itself and the principals that make it reliable. Without knowing those principals it can make an overflow difficult to build especially on the first try. A 4” diameter inner overflow compartment for instance (600 gph) will work just fine, but NOT in comparison to a ‘coast to coast’ overflow. So absolutely YES lineal inch of overflow circumference does help but I doubt it has everything to do with the functionality. I couldn’t imagine using less than 4” anyways :)

I just did some small calculations and if one was to have a:
4” dia overflow then that would be approx 12.56” circumference
3.5” diameter would be approx 10.99” circumference
3” diameter would be approx 9.42” circumference
2.5” diameter would be approx 7.85” circumference
2” diameter would be approx 6.28” circumference

[Satori]

There's an overflow calculator here on RC:
http://reefcentral.com/calc/drain.php