Overflow dimensions?

Discussion in 'Equipment' started by DurTBear, Jan 20, 2010.

  1. DurTBear

    DurTBear Guest

    Still deciding between an external or internal overflow for the future 120g upgrade. Starting to think I might now go with an internal overflow even though I prefer external so that you have more tank space. But the reason I'm starting to think about an internal overflow is because I plan on putting the tank up against a wall and if I have an external overflow, it will protrude out of the back of the tank and might not look as good since there will be a larger gap between the tank and the wall in addition to the plumbing being exposed. Still have to do some more thinking about it...

    Anyway, if I go with an internal overflow, what depth (front to back) do people normally go with? I'm planning to have 3 holes for 3 standpipes (2 holes for the herbie style overflow and the 3rd hole for an emergency standpipe). Not sure how big the holes should be for a 120g tank yet. But what's the narrowest dimensions I can get away with so that I use as little space as possible while still being able to work with the standpipes if I need to?
  2. xcaret

    xcaret Supporting Member

    Are you planning on anything hanging from the back like wires, plumbing, etc?
    I've seen external OF boxes and look just great, they free precious space inside the tank.
    A stand and canopy deeper than the tank itself would help solve the gap between tank and wall;
    and by the sides of the tank a black plexi covering tank to wall to hide cables and what not.
  3. melly mel

    melly mel Supporting Member

    Not sure how much this will help you but I'm currently working on a similar size tank and will be going with 2x 1" stockmen drains (one for main drain and the other for emergency). I was going back and forth on internal and external as well and ended up going with external as I want the least amount of flow obstruction, Plus it clears up ALOT of space inside. O/F dims I'm going with will be 14"x5"x6". Having a very clean background was a major deciding factor for me since I will be going with a dark blue back.

    Not sure how long you plan the o/f box to be but I think 5" to 6" front to back will give you ample space to be able to tighten/loosen bulkheads. I'm also digging xcarets idea of the stand and canopy being deeper than the tank so it doesnt look like such a big gap from the wall. I may have to use that idea for my stand! :bigsmile:

    Hope that helps a little.
  4. sfsuphysics

    sfsuphysics Supporting Member

    Well if you do an external and would like to hide the ugly stuff you can always do a molding along the side that you could remove to access it if you need to, either wood, or acrylic to match the tank.
  5. DurTBear

    DurTBear Guest

    Mike, I like your idea of the molding. I think I will defnitely do that when I get a stand/canopy built for it.

    I think there will definitely be pipes/wires running up it so hiding all of that stuff would be nice. The return pipes will definitely be included although I'm not sure if I want to drill holes and plumb the return directly into the tank or possibly have them go over the rim and down into the tank. There shouldn't be too many wires since I plan to have all of that stuff in the sump but there will be cords running up to the lights/fans/etc.
  6. xcaret

    xcaret Supporting Member

    This person has the overflow in mind for the 72BF, note the stand is deeper and the space between back of the tank and edge of the stand will be covered with a piece of wood/trim. He's telling me the tank is tempered glass since I suggested drilling it for an OF box, still I think the back of the BF tanks is not tempered glass.

  7. DurTBear

    DurTBear Guest

    If I go with 1" overflow, should I do 3/4" return holes? I'm thinking of running pipes over the back of the tank through holes in the acrylic eurobrace with a syphon break. I thought about having drilled holes on the back of the tank with check valves but I'm still nervous of too much water flowing back into the sump when I turn off the return pump.
  8. Ibn

    Ibn Supporting Member

    You can do that. Not sure how far you are from Boun's place, but the way we set up the tank, it uses 2 returns fed off a central tee. Each side enters the tank via two holes already drilled in the eurobrace with a siphon break.
  9. DurTBear

    DurTBear Guest

    Not too far from Boun's place provided it's not during rush hour since the Bay Bridge separates us. But I'll have to go check it out sometime. That's exactly the design I was thinking of. Did he use 3/4" pipes for his return system? And how big do the holes need to be to fit the 3/4" pipes? Are 1" holes too big? I just know you have to account for a little wiggle room.
  10. Smitty

    Smitty Guest

    I also am currently designing an overflow and return system. I decided to go with the glassholes overflow box. It is kind of a hybrid internal/external overflow system. The overflow box itself uses a 1 inch baffle. The returns I plan on drilling up near the top for 3/4 inch bulkheads. The 3/4 inch bulkheads need a 1 1/2 inch glass hole saw. The 1 inch baffle needs a 1 3/4 inch hole saw. I am going to have an open top tank and don't want the returns coming up over the rimless tank. I will have the returns as close as I can to the top with loc line returs pointed at the surface. When there is a power failure there will be some sump drainage . That is why I have a sump big enough to handle the load. As Mike suggested with your setup plans. A deep canopy/stand with a board to hide things sounds great. External is the way to go if you can make it work Asthetically.
  11. xcaret

    xcaret Supporting Member

    You should have 3/4" return. Tees and elbows reduce flow significantly on an already cramped 1/2".
    If I was to do my return again 3/4" but I'm ditching the 46 so the new one has 3/4"

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