Horizontal (Calfo-style) Internal Overflows

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?

bettababy

This is a question I need to run past my husband before I answer it. He does most of my plumbing for me when I need it, even when we design it together. He's been plumbing tanks for at least 20 yrs now, and he knows the best of everything to make it easy, as cheap as possible, and most effective. He also works as head of tech support for Allglass/Oceanic, so I'm sure he and the others are more familiar with the other types of designs and flaws that are out there.
I'll consult him tonight and post as soon as I can.

bettababy

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.

jtma508

Thanks Rob and Dawn. Rob, I emailed you some questions and comments realtive to your advice rather than posting it here.

bettababy

For the sake of the board and any members who are following this thread, can I please ask you to post your questions here? I am just as available to answer everything here rather than private email.
If you need to contact me for something special, a PM here is fine.

jtma508

Some points on my overflow thinking and research:

No ‘teeth’ on the overflow. I’ve read that the smooth top edge disturbs the water surface less and helps with lighting. The teeth only add to the turbulence of the water going into the overflow. No advantage in that. As you mentioned, placement of the top edge is critical in setting the final water level in the tank. I get all the basic plumbing concepts (i.e., shutoffs, unions, no 90’s, etc.). I love your idea about keeping the bulkhead 90’s loose so they can be adjusted for angle. I’m curious why you would suggest orienting them upwards rather than downwards. My initial idea was to avoid a 90deg intake at all by using 1” inside slip bulkheads and fabricating the intake from a straight piece of 1” PVC with an end cap and cutting out the bottom 1/2 longitudinally except for maybe the last ½” of the cap. If that opening is 2” long (assuming I’m building an overflow that is 3” back-to-front) that would provide an opening that is straight (no 90deg) and 64% bigger than a 1” 90deg elbow (2sq in v. 1.2 sq. in). And by not welding the fitting into the slip bulkhead it could be rotated as needed. Again, is there a reason to orient it upwards as you suggested?

I presume that your suggestion of going to 7 or 8in is in regards to the back-to-front dimension. I can see that reasoning as far as rescue is concerned. Increasing that dimension would also allow the overflow intakes to be increased inch-for-inch if I went with my straight design.

I plan on fabricating external durso-style standpipes to attach to the overflow bulkheads. I’d use a sanitary tee at the bulkhead (to avoid the hard 90) and run to a manifold TBD to supply the sump. What’s your thinking on the need to ‘tilt’ standpipes? Does it really make them quieter? I don’t think I want to use over-the-back returns. I think I’d rather use bulkheads (understanding that I’ll need to use check valves to prevent back-siphoning into the sump in case of a pump stoppage since drilling would no longer be an option).

Thanks again for both your and your wife’s help and input, Rob. I just want to be sure I think this through thoroughly so I don’t end up having to make major changes after the tank is up.