Silent and Failsafe Overflow System
- Thread starter JohnL
- Start date
OllieNZ
New member
The Herbie drain on my nano was put to the test yesterday. I came home to the sound of water thundering out the emergency drain (usually dry). Tweaking the ball valve on the syphon channel seemed to make no difference, until I opened it fully and a cerith shot out the end. Flood avoided 
OllieNZ
New member
Amen to that.
A redundant system may seem ott but I'd rather over engineer than suffer disaster.
MidwesternTexan
Average Joe
Proud to say, that my 'version' of the Herbie,* more closely to a BA that combines the 2nd and third drain is Still working VERY well!
When I power off (feed mode) the DC15000 for frozen feedings,
It cranks back up itself.
The 'siphon' is running full siphon yet, so my C2C overflow quickly fills near the top.
OH- but I have a 2nd line- that has an air valve drilled in the top of one of the sanitary 90's- with the free end inside the C2C overflow near the top.
The water comes up in the C2C- the free end of the tube near the top of the C2C goes underwater.
This quickly turns my 2nd drain (wide open, no valves) into an instant full siphon!
Yes- it does 'gurgle' for about 15 seconds- within 1 minute/less usually-
my 'full siphon' runs well- full siphon- and
the whole system quickly stabilizes in under a minute of power back on.
I DON'T adjust anything. It has NEVER given me any accidents/wet floors!
Just another way to do it- and yes, the reduncancy of the 3rd line IS better.
I called it 'The Todd', and yes, it is just a version of the priciples of the Herbie-
but it's not really the same, more a BA with the 2nd and 3rd combined.
And it is Silent too!
Flame Suit Engaged!
When I power off (feed mode) the DC15000 for frozen feedings,
It cranks back up itself.
The 'siphon' is running full siphon yet, so my C2C overflow quickly fills near the top.
OH- but I have a 2nd line- that has an air valve drilled in the top of one of the sanitary 90's- with the free end inside the C2C overflow near the top.
The water comes up in the C2C- the free end of the tube near the top of the C2C goes underwater.
This quickly turns my 2nd drain (wide open, no valves) into an instant full siphon!
Yes- it does 'gurgle' for about 15 seconds- within 1 minute/less usually-
my 'full siphon' runs well- full siphon- and
the whole system quickly stabilizes in under a minute of power back on.
I DON'T adjust anything. It has NEVER given me any accidents/wet floors!
Just another way to do it- and yes, the reduncancy of the 3rd line IS better.
I called it 'The Todd', and yes, it is just a version of the priciples of the Herbie-
but it's not really the same, more a BA with the 2nd and 3rd combined.
And it is Silent too!
Flame Suit Engaged!
uncleof6
Active member
On the side glass, which of these would work?
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Just looking at it without a good point of reference, I would say the first one will work, and you are going to run into problems with the second and third.
Better points of reference would help a bit...
nanomania
New member
What problems would i be facing? Failure or sound?
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uncleof6
Active member
Really, a better point of reference is needed. However it appears that the 2nd and last are a vertical arrangement.
What problems would you be facing? Failure, sound, failure to start, failure to restart. It is entirely unpredictable as this deviates from the design criteria, and all bets are off. BAʻs system thrives because it is very predictable, till you change the recipe.
What problems would you be facing? Failure, sound, failure to start, failure to restart. It is entirely unpredictable as this deviates from the design criteria, and all bets are off. BAʻs system thrives because it is very predictable, till you change the recipe.
pfoxgrover
New member
What would be a good height for an external coast to coast overflow box? It will be four foot long and I was thinking around eight to ten inches tall.
-Paul
-Paul
sleepydoc
Team RC
"External Coast to Coast?" not following you. The weir over which the water flows is what's important. The external box can be whatever size you want as long as it works with the plumbing. Most people have a long or coast to coast internal weir and then a smaller external box. Remember, the larger the box, the more water will drain down to your sump. A 4' x 10" x 4" deep external box will hold 8 gallons of water - that's in addition to the amount of water in the internal box and any back siphon from the tank via the return line. A larger overflow box also means you potentially need to increase the size of the return section of your sump so it doesn't run dry during startup.
pfoxgrover
New member
I guess it is not exactly a coast to coast overflow. There will be no box inside the tank, instead the weir will be a series of four 1" tall by 10" long slots in the back side of the 5' x 5' x 24" square tank. The bottom of the slot will be 1.5" below the tank top and a slotted grate covering it to prevent snails and crabs from making it to the overflow.
That is a good point about the excess water going into the sump, I will double check my measurements on the sump surplus volume.
I don't want to make the external box any taller than I need to, but I also don't want to have issues with starting or maintaining the siphon.
Thanks for the help,
-Paul
sleepydoc
Team RC
Ok - Now I get it. A couple questions - is the tank built or being built? is it a rimless, rimmed or eurobraced? Such slots will weaken the tank wall somewhat. I can't say how much, but it's a concern. The general guideline for drilling holes is one diameter away from the edge of the glass, preferably more, so your proposed setup is cutting things tighter than would be recommended.
pfoxgrover
New member
It is an acrylic tank that I am building with 4.5" euro bracing including a center brace crossing the tank like a "+" sign that will be 6 or 8".
I haven't cut the slots yet but I built a router jig to cut them already.
The external box will be made from 1/2" acrylic and I will reinforce it with some braces between the tank back and the overflow back.
I have built quite a few tanks before but this is going to be my first one with an external overflow and first one with a BA.
I know the slots will weaken the tank back but I believe the 2" breaks between the four slots and the strengthening from the overflow box will balance that out.
I appreciate the feedback.
sleepydoc
Team RC
Ah, ok. So you would end up with 40 linear inches of weir for a 375 gallon tank. I've never seen a hard rule or guideline for the number of inches of overflow per gallon. Like everything, it depends on a lot of things I've seen successful 300 gallon tanks with dual corner flows (probably about 30" total,) so your design certainly could work. Square tanks are inherently more limited Since they have a smaller perimeter to volume ratio. Any reason you don't want to put a narrow coast to coast weir with holes for the water to flow through?
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pfoxgrover
New member
I want to make the overflow as invisible as possible and I want to make it impossible for fish and inverts to get into.
uncleof6
Active member
With four 10" slots, covered by slotted grates, the linear inches of weir would be reduced to the sum of the space water can pass through. Depending on the width of this space, the linear length could be reduced to as little as 1/3 to 1/4 of that 40". This is the "effective length," and is the only number that is relevant.
Since weirs involve water in motion, having a rule of thumb or guidline relating tank volume to weir length would not make any sense. Since a weir is a device used to alter flow characteristics, and provides a simple method to determine open channel volumetric flow rate, we could infer an indirect relationship between volume and weir length using arbitrary rules of thumb concerning volume and flow rate. However, this would not really solve much, as the volume vs flow rate debate has gone on for years, with no resolution, and no doubt will continue for years to come.
Saying "successful x size tank at y inches of overflow", is too subjective to be used as a data point, and "failed x size tank with y inches of overlfow," is just as likely. When it comes to corner overflows, these are not installed based on the system as a whole, or the degree of benefit, rather it is based on what will sell in terms of visual appeal. So we need another method to determine what benefits the system the most. This of course lands right in the middle of physics.
On Bean's website, there is a sidebar that explains the "why" in a rather easy to understand way. This why has appeared in this thread and others a multitude of times, so there is little to gain from reiterating it again; but there is an indisputable guideline that relates tank size, flow rate, and weir length. It is indisputable because it is based on physics, (includes physics that drive some of the sub-systems we use) rather than opinion, anecdote, visual appeal, or convenience.
Simply: For any given flow rate, in any given size tank, the longer the effective length of the "weir," (overflow) the more benefit it will be to the system. Thus we can conclude that the most benefit will be achieved by a weir that is the full length of the longest side of the tank.
Even considering the nature of this guideline, many like to debate the "coast to coast." These debates are invariably driven by varying degrees of opinion, anecdote, visual appeal, and convenience. Usually, it comes in the form of "how much is needed;" the answer is pretty obvious: what is needed is what provides the most benefit. In the end, this is probably one of a very short list of "rules-of-thumb" and/or guidelines that actually have some useful meaning.
http://www.beananimal.com/projects/silent-and-fail-safe-aquarium-overflow-system.aspx
Since weirs involve water in motion, having a rule of thumb or guidline relating tank volume to weir length would not make any sense. Since a weir is a device used to alter flow characteristics, and provides a simple method to determine open channel volumetric flow rate, we could infer an indirect relationship between volume and weir length using arbitrary rules of thumb concerning volume and flow rate. However, this would not really solve much, as the volume vs flow rate debate has gone on for years, with no resolution, and no doubt will continue for years to come.
Saying "successful x size tank at y inches of overflow", is too subjective to be used as a data point, and "failed x size tank with y inches of overlfow," is just as likely. When it comes to corner overflows, these are not installed based on the system as a whole, or the degree of benefit, rather it is based on what will sell in terms of visual appeal. So we need another method to determine what benefits the system the most. This of course lands right in the middle of physics.
On Bean's website, there is a sidebar that explains the "why" in a rather easy to understand way. This why has appeared in this thread and others a multitude of times, so there is little to gain from reiterating it again; but there is an indisputable guideline that relates tank size, flow rate, and weir length. It is indisputable because it is based on physics, (includes physics that drive some of the sub-systems we use) rather than opinion, anecdote, visual appeal, or convenience.
Simply: For any given flow rate, in any given size tank, the longer the effective length of the "weir," (overflow) the more benefit it will be to the system. Thus we can conclude that the most benefit will be achieved by a weir that is the full length of the longest side of the tank.
Even considering the nature of this guideline, many like to debate the "coast to coast." These debates are invariably driven by varying degrees of opinion, anecdote, visual appeal, and convenience. Usually, it comes in the form of "how much is needed;" the answer is pretty obvious: what is needed is what provides the most benefit. In the end, this is probably one of a very short list of "rules-of-thumb" and/or guidelines that actually have some useful meaning.
http://www.beananimal.com/projects/silent-and-fail-safe-aquarium-overflow-system.aspx
Many people are building their tank to be visually appealing, not to perform a physics experiment, so it should be of no surprise to you that many will choose a compromise between form and function. If it quietly handles the flow from someones pump and there's no obvious surface film, and is failsafe / starts up properly every time, that's often enough to be considered "success" for many. The customer is always right.
If what is needed is what provides the most benefit, ultimately you end up needing an entire ocean to satisfy. A tank is already a compromise to begin with. Where do you draw the line with that? The argument should simply be for "as much as possible." Short of that, it should be enough to handle the flow rate and wide enough that it's skimming from more than just a small corner of the tank, if possible.
The rest, and bringing physics into this, is quite simply over-complicating the argument. It's a slippery slope argument. If C2C is best, then how about a C2C that wraps around the entire tank instead of just the longest side, that's technically "even better" right? I don't see anyone proposing this though, even though physics would probably show "it's better". There are points of diminishing returns and designs that are simply impractical. For many people, even a C2C is impractical. I think it helps to bring perspective into this argument as opposed to jumping to the extreme of what's best in a purely theoretical notion.
If what is needed is what provides the most benefit, ultimately you end up needing an entire ocean to satisfy. A tank is already a compromise to begin with. Where do you draw the line with that? The argument should simply be for "as much as possible." Short of that, it should be enough to handle the flow rate and wide enough that it's skimming from more than just a small corner of the tank, if possible.
The rest, and bringing physics into this, is quite simply over-complicating the argument. It's a slippery slope argument. If C2C is best, then how about a C2C that wraps around the entire tank instead of just the longest side, that's technically "even better" right? I don't see anyone proposing this though, even though physics would probably show "it's better". There are points of diminishing returns and designs that are simply impractical. For many people, even a C2C is impractical. I think it helps to bring perspective into this argument as opposed to jumping to the extreme of what's best in a purely theoretical notion.
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