Calfo Style Overflow boxes

Those plastic overflows are all internal, so they're not carrying much load. Since the water level is lower inside the overflow than outside, the water pressure is actually helping keep the plastic or acrylic in place.

I would be loath to try to silicon an acrylic overflow to the outside of a glass tank, where that silicon is directly bearing the weight of the water in shear.

Dan
 
but there is some pressure from below. normal overflow goes to the bottom so the pressure is purely horizontal.

anyway, it would probably be fine. the point is maximum security would be with using glass. just like people use hang on overflows with success, but yet we go through the trouble of drilling our tanks for overflows for some security.
 
It think a non-top-to-bottom overflow would actually have MOST pressure pushing it up. Like a boat.

I agree with the general opinion that silicon on acrylic is fine when it's inside the tank, like a baffle or overflow. I would not try to build a tank out of silicon/acrylic when acrylic solvents are available to do a better job. For glass/acrylic bonds, I wouldn't do it where watertightness and pressure are involved, but would have no problem using it for stuff like overflows (where watertightness is not all that important, since leaks are slow compared to the flow of the drain and overflowing water).

My Oceanic has silicon (or something that looks like silicon) holding the (STUPID OVERSIZED) mega-flow overflow box in place (inside the tank).

V
 
I had an acrylic overflow put on with silicone. When I went to pull it off, it was on so tight I was able to actually break the acrylic before the silicone let go. I don't think that would let go under normal circumstances in the tank.

I've heard a few ways to improve the bond. One is to rough up the acrylic with 220 grit sandpaper, and then put some clear PVC primer on the area you roughed up. That should help it stick a bit more.

Another option is to use Dow Corning 795 silicone/building sealant. But that stuff is very hard to find unless you have a construction or glazing place nearby that carries it. It also takes like 14 days to cure.
 
I agree, all my overflows are glass/glass... this allows me to get the previously mentioned BLACK glass. I really like the look, the only problem with glass though is that you cannot cut the notches in the top, as you can with acrylic. I also have tried silicone acrylic to glass.. no truely promising results... an occasional success, but random. Anyone doing so, should get themselves insured, as sooner or later they will flood themselves, or some other poor soul. I think about an overflow on my system breaking off the ourside... this would drain the tank down 4-5" plus everything in the sump that is being returned. 65 gallons... maybe more... NO THANK YOU.

I see the point you are making about siliconing the overflows INTO a system like those from ALL-GLASS and OCEAINIC and others...

Picture this... make a 10 gallon tang with acrylic and held together with silicone. float it like a boat. The water pressure will keep it together.

Now.. fill the same tank with water... and wait... it will eventually fall apart or leak.

BTW, I like to scrape the algae or coraline off my overflow from time to time, try that with acrylic without scratching or breaking it.

J
 
Glass might not be as difficult to "notch" as you thing. With a dremel and diamond dust cutters (not expensive) you could probably do it.

Also consider that you can make "teeth" (or not, why do you really need teeth, except to keep critters out?) with other things. For instance, if you made your overflow with glass, then made a toothed (thin) acrylic piece, you could silicon (on the flat side) the acrylic teeth to the glass. So the siliconed glass will provide structural support, and the silliconed on acrylic can provide teeth.


V
 
Yeah, I don't put teeth in them anymore.

As for the going arguement about my overflows being bonded with silicone, even if the gave way, my tank would only drain 2" more than it does now. No big deal, and definatly not a disaster like a hangon overflow lossing siphon, and pumping all the sump water on the floor!
 
Here's my new boxes, they don't take up as much room in the tank as the one's I posted before.

tank34jp.jpg
 
Thanks. These new ones are still 17" long, and 4 1/4" tall, but only a little but over 2.5" wide. The only ones were almost 4 3/4", so I saved around 2 1/4" in the tank. I like the look much better.
 
on my 48" overflow i plan on running 3 holes out just because there already drilled so will having so many holes (2" plumbing) and only Mag 9.5 as the return will i have noise issues if i ran the not as wide box with out a elbow? im looking for best way of plumbing the not as wide box.

so will more or less flow through the holes without elbows be quieter?
 
<a href=showthread.php?s=&postid=6313985#post6313985 target=_blank>Originally posted</a> by trmiv
Thanks. These new ones are still 17" long, and 4 1/4" tall, but only a little but over 2.5" wide. The only ones were almost 4 3/4", so I saved around 2 1/4" in the tank. I like the look much better.
Click to expand...

How many gasket do you use to install bulkhead ?

I built my overflow box just like you but I want to add another gasket between the back of the overflow box and the back tank wall. Use 2 gaskets total (both inside the tank). You will see the gap between the back of the overflow box and the back tank wall.

I want to know if this is the best methold to add another gasket to prevent the leak.
 
I've just discovered this thread, didn't know they were called Calfo's, but they work great for my CLS. Acrylic to glass seems to work good here, and a reason for them to be fairly wide is so you'll have a place for frags! I kind of wish I'd put a small shelf on the bottom, but glueing to the front has worked well, until you have to clear the slots with a knife because sps has covered them up These have been in operation for two years.
greeniesintheoverflow120704post.jpg

acclimatingintheclsoverflow072005.jpg
 
I took the in tank portion of an old overflow box, drilled it and the tank with the same bulkhead template and used two 1" bulkheads to attach the overflow box to the aquarium in an AGA 120. I then used aquarium silicone to go around the edges of the box that were against the glass. The silicone is just there to keep detritus and other things from getting in between the back of the box and the aquarium itself. Works like a charm. I will be constructing my own overflow box for my new "In Wall" 180 which will have basically the same design. Question I have is what is the minimum length, width, and depth to provide adequate surface skimming with around 1000gph return and three 1 1/2" bulkheads?
 
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