Calfo Style Overflow boxes

[WarrenG]

Instead of adhering pieces of flat glas or acrylic to the tank to make the horizontal box overflow, how about using a pipe "90 degree bend" from the bulkhead joined to a "T" at the water surface, then installing a length of 2" diameter pipe into each horizontal inlet of the "T"? Put a cap on the outside ends of the pipes. Use a table saw to cut multiple slots in the top half of the pipe (before installation!) about 1/2" deep, perpendicular to the length of pipe.

Using slip fittings on the water level "T" would allow for removal and cleaning of the pipe and its slots.

I haven't tried this, but it seems simpler and more flexible than the box method of horizontal overflow.

Black PVC parts and pipe are available online.

 

[Jeremy Blaze]

It could work but would be less effective in skimming the surface, and seems like it would be easier to clog and cause an overflow. But I have not tried it so I can't say for sure.

 

[markjd]

I have a 120G. I removed my old internal high walled overflow box of 24"L x 8"D x 5"H on the weekend. Added a new coast to coast overflow of approx 48"L x 2.25"D x 4"H. Greatly improved the look of the tank. Looks much more open from side to side

Hell of a job doing it with a tank half filled with water! Removed about half the water from my tank. Cut the old glass box away with a box cutter. Measured, marked, laid masking tape in place, laid silicone, placed glass, supported glass on vertical pvc pieces, and let cure overnight.

Couldn't have done it without help from a friend. But next time I think I'll do it right the first time, and not do it with a tank half filled with fish and coral

 

[brackishdude]

Impressive, Mark.

How well did it level?

Mine was off, so I placed a bead of silicone on the top lip of the weir and laid a sheet of drycleaning plastic over it, to prevent sticking to the level/straightedge I used to press down lightly until level with the water. Its still a bit off, but the layer of silicone (with the plastic on top still, trimmed of course) is < 1/8" at its thickest. Water pours over the whole length of weir.

I coated the front of the silicone band with more silicone and stuck sand on to disguise it (see page 2 for my stone wall background). Either way I think its a great low tech way to correct a likely-common prob, esp if you ever move your tank.

 

[vdubfiend]

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tagged

 

[markjd]

<a href=showthread.php?s=&postid=8072587#post8072587 target=_blank>Originally posted</a> by brackishdude
Impressive, Mark.

How well did it level?

Level is not perfect, but close enough for now Water travels over the top of the weir for the whole length.

 

[stereomandan]

I read through this thread, and have one question. Why is everyone making the overflows so dang long? I thought the idea was to make more room in the tank and make the overflows unobtrusive? Seems as though 12" wide is about the max someone would need. Remember, the glass/acrylic/silicon will get algae on it, and won't always stay nice and clear. It will be noticeable. I like the idea a lot, but if I do one, it's only going to be about 8" wide, max and in the corner.

Dan

 

[marduc]

The rationale for the longer overflows is to get as thin of a layer of water possible overflowing the tank. This thin layer of surface water then will be more concentrated in proteins since proteins accumulate at the air/water interface.

 

[brackishdude]

Using the minimum hieght needed for your set up, modifying your downturned elbow to take up as little front-back space as possible, tapering the box at the bottom, or the inside&outside box model (mine, page twoish) are ways to decrease the space taken up by your box.

I'll agree that drilling the bottom and using a "tower style" overflow is painfully wasteful of space, and that using a similiar footprint, but instead mounting it up high on the wall, goes a long way to reclaiming that space. But the other shorcoming of that tower is its incredibly narrow area of actual overflow, especially on models with teeth are as wide as the slits themselves.

The calfo design allows you to reclain the space but also take maximum advantage of the surface area that does not lie with the field of view: the back wall. More surface turnover = cleaner water.

 

[jake2045]

Calfo over flow

Calfo over flow

Heres mine installed on the AGA 180.

 

[stereomandan]

I don't think having a thin sheet of water, versus a thick sheet of water, is going to make any difference to the skimming capability. It's going to be a minute difference, if any. I LOVE the idea of the Calfo overflow, but there is NO reason for such a large width for the overflow. the surface is going to get skimmed plenty either way.

My 38g has a tiny overflow with no teeth. It's maybe 5" wide, and I don't have any build up on my water surface, and I'm only running about 200 gph through the overflow.

Dan

 

[brackishdude]

Jake, very nice!!

smd, I find it difficult to find fault in your logic.

How about this, then: the water height difference in the display tank between pump-on and pump-off will be greaterwith a narrower overflow, requiring mmore sump space when the pump is off. I'm reachin' here.

 

[stereomandan]

<a href=showthread.php?s=&postid=8149205#post8149205 target=_blank>Originally posted</a> by brackishdude
Jake, very nice!!

smd, I find it difficult to find fault in your logic.

How about this, then: the water height difference in the display tank between pump-on and pump-off will be greaterwith a narrower overflow, requiring mmore sump space when the pump is off. I'm reachin' here.

Well, I suppose if water height in your sump is that critical, then you are correct. Personally, I always allow plenty of room in the sump for any back siphon or water height difference from the overflow.

I just think a lot of people may be fustrated later when that big wide overflow gets a nice film of algae on it. Since it's close to the lights, it's going to be prone to algae, and will require constant cleaning to keep it from being noticeable. A narrower version will serve the same purpose and won't look ugly later if you place it in the corner. Just my thoughts.

Dan

 

[jerryz]

Why would the water height difference between pump on and off be greater with this method? I thought the point was a long thin sheet. If so wouldn't that mean this would actually cause the skimmer to stop skimming earlier in a pump off situation since it's closer to the surface with a longer thinner sheet of water? Or did I miss something?

 

[ReefMeister2]

jerryz is correct,
assuming there are no teeth....the Calfo style overflow would drain LESS water back to the sump in a power off situation. (higher water level is retained within the display tank)
"Length" of the overflow is completely irrelevent as to how much free flow occurs after a shutdown

 

[Name That Tune]

Hey! I've been making similar overflow boxes on my tanks for years now, i'didn't know that they were called that.

who-da-thunk-it

 

[hahnmeister]

I dont know that they are really called 'Calfo' style overflows. Anthony Calfo does suggest large linear/horizontal overflow use to achieve target skimming of the thinnest layers from the top of the tank, and then direct feeding these protein and oil rich layers directly into a skimmer.

Similar to this is a type called 'Cali' Style. This is where the holes are plumbed the same in the back, but each bulkhead gets its own 6" box overflow over the bulkhead. Good examples are shown here: http://barraquatic.com/overflows.php

I think somewhere in the process one name was superimposed on the other and thats where we are today. I just call them horizontal overflows myself, or linear overflows.

 

[joelwalk]

I was looking in different thread, and a guy mentioned the idea of using a large piece of PVC pipe cut into quarters for the overflow instead of glass or acrylic. I would think that this would be easier to silicone in, but that's just me.

I just thought I would pass this along.

Joel

 

[hahnmeister]

Ive seen it done multiple times. There is a nano that has that as well. You could run it lengthwise across the back of the tank for a calfo style as well with a nice rounded bottom.

 

[ReefMeister2]

<a href=showthread.php?s=&postid=8156506#post8156506 target=_blank>Originally posted</a> by joelwalk
I was looking in different thread, and a guy mentioned the idea of using a large piece of PVC pipe cut into quarters for the overflow instead of glass or acrylic. I would think that this would be easier to silicone in, but that's just me.

That is an intriguing idea but I don't think it would be appropriate for larger tanks. The problem is insufficient linear inches of overflow teeth.
for instance:
a 6" diameter pipe cut in half yields 9.42 linear inches available for overflow, which translates into ~600 gph max. that could run through the teeth.

a 8" pipe cut in half yields 12.56 which translates into ~800 gph max. that could run through the teeth.

I suppose you could install multiple pipe-overflows to get sufficient capacity, but even that would be on the weak side. I do admit that the radius-shaped overflow box would be more aesthetically pleasing

Now, linear style???
that's a whole different story! I'd love to see one installed horizontally and hear from someone who's experienced the "quarter-pipe/linear/calfo-style" overflow. Again, I think the radius shape would look awesome! Hmmm, that would have roughly half the volume of a comparable "square-shaped" linear overflow.....I wonder how it would affect performance of the overflow. Anybody?