External over-flow. Is it a mistake?
- Thread starter stallen
- Start date
External overflows are probably thought of a mistake simply by the mechanism to which they pull water out of your tank, and that's via a siphon. Siphons by design need to be kept full of water for them to work, there is no "restarting" them naturally, unlike a drilled tank where all you need is water to go as high as the hole that's drilled. Also siphons have a tendency to pull air bubbles into them, this is going to happen simply because as water falls over the edge of the skimmer box it'll pull air down under the water which can get sucked into the siphon and occasionally bubbles will not make it through, choosing to sit at the "high point" in the siphon tube, as bubbles form the siphon slows down, eventually however it breaks when too much air gets in there and you're screwed.
Now there are ways to circumvent a lot of these issues, using a venturi on a pump connected to your siphon tube to pull air out, using that to "kick start" the siphon should it ever fail, but when it comes down to it you probably want everything kept as simplistic as possible, and that usually means drilling holes. When it comes down to it you have to ask the question, are you willing to risk the volume of water in your sump going onto the floor? I said yes, and paid the price quite a few times.
Now there are ways to circumvent a lot of these issues, using a venturi on a pump connected to your siphon tube to pull air out, using that to "kick start" the siphon should it ever fail, but when it comes down to it you probably want everything kept as simplistic as possible, and that usually means drilling holes. When it comes down to it you have to ask the question, are you willing to risk the volume of water in your sump going onto the floor? I said yes, and paid the price quite a few times.
stallen":1j2ulgb4 said:
That was me, and I stand by it. They're more prone to failure that can cause a pump to burn out, or a flood, or both. In addition, a drilled overflow is usually cheaper, especially if you can drill the glass yourself! If you own a dremel tool, it's actually very simple to do.
This is sort of what I have in mind for an external overflow.
I can't take credit for this sketch. It's ninjafish's sketch and he is currently using this on his new tank.
Here is a pic of the inside of his tank (he is just starting the tank). You can see how clean this external overflow makes the display look.
Basically you have two 1" PVC intake pipes in the external overflow. One of the intakes is much lower than the other. The lower intake is control by a gate valve. You adjust the gate valve to keep the water level in the external over-flow box in between the two intakes. This prevents air from being sucked into the lower intake. The upper intake is only a back-up just in case the lower intake gets clogged and the water level rises too high (to prevent overflow onto the floor).
Most people's first thought is that there will be constant adjusting of the gate valve, but people who use this method swear that they go months without any adjustments; once you dial it in correctly, it stays at that level. Also, users of this method claim the upper intake never gets used, but it makes them feel better to have the back-up drain.
As a bonus this method is supposedly very quiet as opposed to the durso drain (even quieter than modified durso's).
Thanks for the responses. PLEASE give me some further thoughts on this!!
This method of over-flow has been called the "Herbie method" over on reef central. Described (in length) here:
http://reefcentral.com/forums/showthrea ... genumber=1
I can't take credit for this sketch. It's ninjafish's sketch and he is currently using this on his new tank.
Here is a pic of the inside of his tank (he is just starting the tank). You can see how clean this external overflow makes the display look.
Basically you have two 1" PVC intake pipes in the external overflow. One of the intakes is much lower than the other. The lower intake is control by a gate valve. You adjust the gate valve to keep the water level in the external over-flow box in between the two intakes. This prevents air from being sucked into the lower intake. The upper intake is only a back-up just in case the lower intake gets clogged and the water level rises too high (to prevent overflow onto the floor).
Most people's first thought is that there will be constant adjusting of the gate valve, but people who use this method swear that they go months without any adjustments; once you dial it in correctly, it stays at that level. Also, users of this method claim the upper intake never gets used, but it makes them feel better to have the back-up drain.
As a bonus this method is supposedly very quiet as opposed to the durso drain (even quieter than modified durso's).
Thanks for the responses. PLEASE give me some further thoughts on this!!
This method of over-flow has been called the "Herbie method" over on reef central. Described (in length) here:
http://reefcentral.com/forums/showthrea ... genumber=1
Thats different than a traditional external overflow. 
A traditional external overflow uses a siphon to pull water up and over the lip of the tank instead of through the wall of the tank. The problem with this is the siphon can break, and you have, well, a problem.
I have been calling what you pictured above an outside overflow, and I love them (they have been around for a while, but haven't been all that popular because they take up extra room outside the tank). If I ever replace my tank, it will have something like it. Actually, Matt and I just built something similar on some smaller tanks.
As for the Herbie method - I'll try to read up on it.
A traditional external overflow uses a siphon to pull water up and over the lip of the tank instead of through the wall of the tank. The problem with this is the siphon can break, and you have, well, a problem.
I have been calling what you pictured above an outside overflow, and I love them (they have been around for a while, but haven't been all that popular because they take up extra room outside the tank). If I ever replace my tank, it will have something like it. Actually, Matt and I just built something similar on some smaller tanks.
As for the Herbie method - I'll try to read up on it.
OK - read a little. The back up is a fine idea - I have used it before (currently in a cpr siphon overflow that has two bulkheads). The only thing I don't like is the gate valve on the drain, but thats me. Some people like them. Me, I don't like restricting the drain and I worry about the gate valve sticking and getting restricted over time, or getting restricted catastrophically by something big enough to get into the drain line, but not small enough to make it past the gate valve. But, like I say, YMMV.
@ Matt_Wandell - Thanks for the response. I was just looking for an explanation of your advise that you gave in the "common mistakes" article. I'm just trying to learn. I currently have a nano tank, but in the very very early planning stage of a much larger tank. Any thoughts on this overflow design as posted above?
@ Thales - Thanks to you as well! Yes, I can definately see the danger of an external overflow that uses a siphon method. "Outside overflow"... Is that more common terminology? Yeah, I can see that would take up more space behind the tank causing problems for a typical set-up. I'm planning this for an in-wall system. Please come back and post your thoughts on that "Herbie over-flow" set-up. There is probably another name for it, but I think Herbie was the first to introduce it to that forum.
@ Thales - Thanks to you as well! Yes, I can definately see the danger of an external overflow that uses a siphon method. "Outside overflow"... Is that more common terminology? Yeah, I can see that would take up more space behind the tank causing problems for a typical set-up. I'm planning this for an in-wall system. Please come back and post your thoughts on that "Herbie over-flow" set-up. There is probably another name for it, but I think Herbie was the first to introduce it to that forum.
Well hell if you're talking an external overflow without any siphons then I'm all for it! Much nicer IMO as it opens up so much space inside the tank. I did this with my 6 foot long acrylic tank, I cut a series of long slats along almost the entire length of the tank, and "glued" (weldon) an over flow that was a little over 5 feet long..... and I did this with water still in tank (yeah I'm stupid/crazy ).
I too thought as Thales did with siphons, of course typically they call those HOB (hang on the back) overflows, but whenever a new poster posts messages probably assumed that's what they're talking about when they say overflows.
).I too thought as Thales did with siphons, of course typically they call those HOB (hang on the back) overflows, but whenever a new poster posts messages probably assumed that's what they're talking about when they say overflows.
sfsuphysics":3krtu3rf said:Well hell if you're talking an external overflow without any siphons then I'm all for it! Much nicer IMO as it opens up so much space inside the tank. I did this with my 6 foot long acrylic tank, I cut a series of long slats along almost the entire length of the tank, and "glued" (weldon) an over flow that was a little over 5 feet long..... and I did this with water still in tank (yeah I'm stupid/crazy
I too thought as Thales did with siphons, of course typically they call those HOB (hang on the back) overflows, but whenever a new poster posts messages probably assumed that's what they're talking about when they say overflows.
Yeah, I'm not a total newb. But I guess I am lacking the proper terminology for this type of over-flow. It's definitely a "custom cut tank with a permanently attached over-flow box without the use of a siphon" 8O I dunno how to boil that down to a couple words :lol: :?:
Yeah, I call those external overflows.stallen":2fja5g5e said:sfsuphysics":2fja5g5e said:Well hell if you're talking an external overflow without any siphons then I'm all for it! Much nicer IMO as it opens up so much space inside the tank. I did this with my 6 foot long acrylic tank, I cut a series of long slats along almost the entire length of the tank, and "glued" (weldon) an over flow that was a little over 5 feet long..... and I did this with water still in tank (yeah I'm stupid/crazy
I too thought as Thales did with siphons, of course typically they call those HOB (hang on the back) overflows, but whenever a new poster posts messages probably assumed that's what they're talking about when they say overflows.
Yeah, I'm not a total newb. But I guess I am lacking the proper terminology for this type of over-flow. It's definitely a "custom cut tank with a permanently attached over-flow box without the use of a siphon" 8O I dunno how to boil that down to a couple words :lol: :?:
Looks good, by the way. 8)
Thats a nice job you got there, I'm not completely convinced that silicone has a strong enough bond to hold any sort of pressure, but of course glass tanks prove me wrong on that one.. so who knows
Any future tank I might have will have that type of overflow, no iffs and or buts.. unless of course it's a 4 side viewable..
Any future tank I might have will have that type of overflow, no iffs and or buts.. unless of course it's a 4 side viewable..
sfsuphysics":345510e0 said:Thats a nice job you got there, I'm not completely convinced that silicone has a strong enough bond to hold any sort of pressure, but of course glass tanks prove me wrong on that one.. so who knows
Any future tank I might have will have that type of overflow, no iffs and or buts.. unless of course it's a 4 side viewable..
Like I said in my second post (with the pictures). It's not my tank. It's a guy on the nano-reef forum that goes by the ID "ninjafish". Here is the link is you are interested: http://www.nano-reef.com/forums/index.p ... pic=101490 I just want to give him the credit. I am just a fan of this and several other tanks that he has done.
Back on topic... Yeah, the glass attached with silicone seems to be the only potential weakness in the plan. I've seem this same type of over flow done with an acrylic tank and acrylic overflow which is probably a stronger bond, but I am most interested in starphire glass.
By the time I am ready to build my tank (probably in a couple years when I'm done with grad school), I will be able to ask several people utilizing this method how it is holding up.
the best thing about the external overflow is you can run the span of the tank with teeth and get all the surface scum off without having to worry about directing flow toward the top of the tank....
i saw one run about a 10' stretch(500g ish tank??) with 10 2" drains.... the guy had a 250g carlson surge on the tank that dumped every 5-7mins.... the thing was nuts. this was on top of his 10,000gph of flow....
i saw one run about a 10' stretch(500g ish tank??) with 10 2" drains.... the guy had a 250g carlson surge on the tank that dumped every 5-7mins.... the thing was nuts. this was on top of his 10,000gph of flow....
stallen":2phz4sbj said:sfsuphysics":2phz4sbj said:Thats a nice job you got there, I'm not completely convinced that silicone has a strong enough bond to hold any sort of pressure, but of course glass tanks prove me wrong on that one.. so who knows
Any future tank I might have will have that type of overflow, no iffs and or buts.. unless of course it's a 4 side viewable..
Like I said in my second post (with the pictures). It's not my tank. It's a guy on the nano-reef forum that goes by the ID "ninjafish". Here is the link is you are interested: http://www.nano-reef.com/forums/index.p ... pic=101490 I just want to give him the credit. I am just a fan of this and several other tanks that he has done.
Back on topic... Yeah, the glass attached with silicone seems to be the only potential weakness in the plan. I've seem this same type of over flow done with an acrylic tank and acrylic overflow which is probably a stronger bond, but I am most interested in starphire glass.
By the time I am ready to build my tank (probably in a couple years when I'm done with grad school), I will be able to ask several people utilizing this method how it is holding up.
Ah, I thought you were talking about a siphon style overflow too.
This idea is great, and it works wonderfully! I have pretty much done exactly what that guy seems to have done.
Any good LFS can get Tru-Vu to custom make the piece of acrylic teeth for you Be forewarned that it will cost a bit--I think mine was $50. A decent window or glass shop will cut the glass for you (and if you're lucky, drill the holes too) for around $20. The difficult part is cutting the slot in the tank. Very time consuming, but well worth it when you're done.
In addition, I have my return plumbing mounted in the canopy and pretty much invisible.
I should have a tank worthy of taking pictures of sometime in the next few months.
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