Choosing a external overflow box.

[sjm817]

Capn, its a little hard to see what your DIY design looks like.
You have to be sure the U Tube is full of water when power is off. This means both ends of the U Tube must be submerged when power is off. The tank side usually takes care of itself. The drain side will need a baffle or a standpipe to keep the end submerged.

 

[Uncle Salty 05]

I dont understand why you would continue to use your U-Tube overflow if it loses siphon every week or two but that's another subject.

The unit is on an 55 gallon algae farm I "inherited" from my neighbor that threw in the towel, it is a single U tube on a HOB wet dry being driven by an Aqua clear 70 (400gph).

My personal experience is my weir style overflow has never failed in over 10 years and every U tube set up I have had over the years has failed at sometime.

It's common sense and its proven in application based on the reports of failures by users of the weir style overflows.

I guess I am just lucky, maybe I will buy a lottery ticket tonight.

 

[DarG]

Overflows all continue to drain the tank until the water level in the tank gets below the edge or teeth of the internal box. Since I am not a scientist, the best I can describe a properly designed U-tube overflow and why it doesnt lose siphon when pump is shut down is due to equilibrium. Proper design between the height of the drain pipes in the outer box and/or the U-tubes in the outer box being contained in their own chamber ... so that water stops draining down to the sump BEFORE the water level in the inner and outer boxes fall to a level below the ends of the U-tubes. Again, I dont know the scientific terms or laws of physics that govern this and I dont pretend to.
Obviously there is a siphon through the utubes between the inner and outer boxes. But it has something to do with gravity and equilibrium so that the siphon stops draining water between the inner and outer boxes yet the water remains in the U-tubes ... I assume because the pressure is equalized in the tubes at a certain point BEFORE the water level drops below the ends of the U-Tubes because of an equalization of the water levels/pressures between the inner and outer boxes.

The key seems to be the U-tubes being in their own chamber in the outer box ... and/or the drain pipes to the tank being above the level of the bottom of the U-Tubes. The Lifereef has the central chamber in the outer box that the U-tubes empty into. And so do the other designs that most people seem to recommend as reliable.

Sorry, I dont know the science. But if the outer box is non chambered which just allows the U-tubes to empty into the open area and the tops of the drains are below the bottoms of the U-tubes then the siphon will continue until the Utubes empty and then obviously they wont resume siphon when power is turned back on. And I dont know if it goes beyond just that and the U-Tubes actually require their own chamber in the external box. Again, I think that all the overflows that seem to be recommended all have this dedicated chamber for the U-tubes to empty into in the external box.

And I realize that this probably doesnt help you at all because I dont know the technical side of it in order to explain it.

Which is probably why I just bought the Lifereef instead of any of the other recommended, less expensive U-tubes based on it having the absolute best reputation of all the external overflows ... this of course after learning a valuable lesson after having an aqualifter pump fail on a CPR overflow and realizing that Murphys law is bad enough without tempting it by hoping I would have better luck with a second aqualifter (and on top of that, also hoping the air fitting wouldnt clog on the CPR).

Im sure one of the more scientific minds could explain it better.

 

[MatthewLaw]

i think that is a pretty accurate description. at least it makes sense and applies when I shut off my return pump to similate a failure to ensure that everything is properly set up.

 

[DarG]

<a href=showthread.php?s=&postid=14918311#post14918311 target=_blank>Originally posted</a> by Uncle Salty 05
The unit is on an 55 gallon algae farm I "inherited" from my neighbor that threw in the towel, it is a single U tube on a HOB wet dry being driven by an Aqua clear 70 (400gph).

My personal experience is my weir style overflow has never failed in over 10 years and every U tube set up I have had over the years has failed at sometime.



I guess I am just lucky, maybe I will buy a lottery ticket tonight.

Its probably not worth the debate but to me it's common sense. I have had an aqualifter pump die while using the CPR. The aqualifter can fail (and this is not what would be considered a rare occurence) and the air fitting can clog ... I have read about failed CPR overflows due to the pump failure or clogged air fitting on several occassions on this forum alone. As well as reports of failed Aqualifters in general.
So one is relying on two necessary, additional variables with the Weir style overflow.

I have never heard or read of a Lifereef overflow failing. I believe that Jeff at Lifereef has never had a report of one of his overflows failing. The design will not fail. My dual Lifereef has not failed in the two years or so that I have been using it. Obviously there are other outside variables that can potentially cause a failure that are not directly attributed to the design of the overflow itself and are outside of user error. But the weir style overflows have two additional issues that are part of the design and can directly cause failure. The secondary pump failing and the air fitting clogging. Both these things have been reported. I have had the pump fail on me personally.

I certainly dont wish for you to have any problems. But again, to me, it is common sense that these two additional variables translate to an increased risk of failure. So I personally would not and do not recommend these style overflows when I throw in my opinion on the topic. And my opinion in these cases is based on actual experience.

 

[Uncle Salty 05]

And my opinion in these cases is based on actual experience.

As are mine.
I have never had a failure in over 10 years with my weir style overflow.(until today I didn't even know that's what they are called).
The U-tube units I have had in the past as well as the one I have now trap air and eventually lose the siphon, can anyone tell me what the min GPH is for a U tube style overflow to yield the needed velocity to stop this from happening?

Plus U tube systems are ugly and clear which allows algae to grow inside them. A black weir style does not have this problem.

 

[sjm817]

The GPH needed varies, but typically, 200 - 250 GPH. Some overflows are just designed poorly and will accumulate air.

As far as the cleaning, that was another thing i didn't like about the CPR. The U Tube is simple to remove and clean. The CPR is one piece. It is very difficult to get into the C channel to clean it out.

Yes, the CPR has a nice low profile, but the reliability trade off is not worth it. If yours has been working for 10 years, I would be happy and continue using it (and go get that lottery ticket!)

 

[Aquarist007]

<a href=showthread.php?s=&postid=14918305#post14918305 target=_blank>Originally posted</a> by sjm817
Capn, its a little hard to see what your DIY design looks like.
You have to be sure the U Tube is full of water when power is off. This means both ends of the U Tube must be submerged when power is off. The tank side usually takes care of itself. The drain side will need a baffle or a standpipe to keep the end submerged.

I guess the problem is that I only have the outer box--no inner box. A stand pipe on the outer box won't stop the u tube from draining the tank down to below the u tube and stopping the siphon.

 

[Aquarist007]

a guy just came up with a great idea on another thread that I think will solve the problem:

http://reefcentral.com/gallery/showphoto.php?photo=272436&papass=&sort=1&thecat=

 

[MatthewLaw]

so i guess connect a U tube to a pump (ex. maijet 1200)

 

[DarG]

<a href=showthread.php?s=&postid=14918665#post14918665 target=_blank>Originally posted</a> by Uncle Salty 05
As are mine.
I have never had a failure in over 10 years with my weir style overflow.(until today I didn't even know that's what they are called).
The U-tube units I have had in the past as well as the one I have now trap air and eventually lose the siphon, can anyone tell me what the min GPH is for a U tube style overflow to yield the needed velocity to stop this from happening?

Plus U tube systems are ugly and clear which allows algae to grow inside them. A black weir style does not have this problem.

I have a black inner box, not a clear one. The Lifereef is available with clear, black or blue inner box.

Properly designed U-tube overflows dont lose siphon unless you dont have enough flow through the system. You have either not owned a well designed U-tube overflow or the flow is too low.

Im glad you have had no problems and hope you dont. As long as the aqualifter never fails and/or the air fitting doesnt clog, you wont have to come home to a soaked floor. Not worth the risk to me, once was enough. Luckily I was home when the aqualifter quit and only overflowed a gallon or two before I saw what was going on and unplugged the return pump.