Originally Posted by jtma508
Researching overflows it seems that the horizontal ones with external durso standpipes seem to perform quite well. The original Calfo design was full length but many people seem to think that is overkill. On a 48in tank I'm tossing around the idea of an 18in overflow centered in the tank that is perhaps 5in tall and 3in deep and with 3 1in bulkheads. Does anyone here have any experience with these and able to offer any guidance as far as dimensions go?
Hello, I am Bettababy's husband. She asked me to answer this one for you. Just a little background on myself. I am the Technical Support Lead for All-Glass Aquarium, Oceanic Aquarium, Kent Marine, and Coralife.
What I get from your description is that you want to do an 18inch wide by 5" tall by 3" front to back. I will go on this assumption.
The majority of a standard overflow box is wasted space and can be hard to catch a fish out of if one jumps into it. you still have the lower section below the overflow for placement of live rock. So your thoughts of a shorter overflow is a sound idea. You might want to go to a 7 or 8 inch deep overflow for easier workability. You will want an initial 90 degree elbow turned upward with a strainer inside the overflow box. It makes it easier for maintenance. Just make sure your slots are placed just right so that when the tank is running the slots aren't so low that you see the upper water line. All you really need for a drain is the bulkhead fitting covered by a strainer. Pentair Aquatics (Rainbow Lifegaurd) sells bulkhead fitting packs that have one bulkhead fitting, a strainer, and a slip-fit hose barb elbow. Each one inch drain can comfortably handle 600gallons per hour. Take that in mind when you are deciding how many drains you intend to install. If all three 1" bulkhead fittings are to be drains then you can pump 1800 GPH into the tank.
Before drilling the tank, make sure that the glass is not tempered. For all Oceanic tanks, the only panel that is tempered is the bottom. All-Glass tanks are a little different. If the tank came from a boxed kit (available up to 55 gallons) then all sides are tempered. Free standing tanks, the bottom is the only tempered panel. There was a period of time about 4 to 5 years ago where some of the tanks had random tempered panes. If the assembler ran out of non tempered glass, or just grabbed the wrong glass, the tank could have a tempered back, side, etc.
Make sure that when you install the bulkhead fittings, that the threads stick out the back of the tank, and that the gasket is on the inside of the tank. Also try to avoid sharp 90 degree angles on your drain pipes. Either use a "swoop" 90 or a couple of 45 degree angles to equal a 90 degree. Sharp 90's tend to be loud when the water drains thru it. The only sharp 90 you should use is inside the overflow box. Do not glue the elbow to the bulkhead fitting. Leave it slightly loose so that you can angle the elbow to adjust sound levels if you experience gurgling when the water drains into them. The returns can go up over the back rim of the tank.
If you use an external drive pump such as a Blueline, TurboSea, Little Giant, Iwaki, Posidon, etc make sure that you have a shut off valve and a PVC union on the intake and output. the fitting series should go as such:
From the sump to a ball or gate valve, to a union, to the inlet of the pump, then on the output of the pump you go to another union to another valve and up to the tank. this will allow you to shut off the valves and remove the pump if ever the need arises. If you decide to run a submersible pump such as a Magdrive pump (E.G. Danner company), or a RIO pump (TAAM company) then you don't have to worry about unions and valves as any water in the lines will drain back into the sump and not onto the floor.
Make sure that any return you use should have about a 3/16 inch or little smaller (but not too small) breather hole drilled into the underside just above or right at the water line. It should be drilled at an upward angle so that any water squirting out of it will squirt downward into the water. If the power ever cuts out to the pump then air will get sucked into the hole and cut off any suction and you won't overflow the sump.
Hope that helps.