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Thread: Overflows

  1. #1
    Senior Member AndrewNS's Avatar
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    Overflows

    I finally got all the plumbing done and the other day decided it was time to fill the new tank with water.
    I started with the sump and put in 30 gals. The bulkhead leaked!! So, I took out all the water and resealed
    with silicone. Yesterday the silicone was dry and I started filling the tank again. I filled up the sump
    almost to the top and turned on the return pump. Everything seemed fine, I looked at everthing to see if there
    were any leaks. When no leaks were found I continued to fill up the sump and tank. When the water level in the
    tank was almost at the top of the overflow I ran out of water. Checked the overflows and there was no water in them.

    After getting more water I noticed that water was running from the overflow pipes to the sump. The water level
    in the tank had not reached the point that it would overflow. So, I ran upstairs to find the tank was draining.
    The overflows leak. I thought I would just wait to see where the water stopped flowing and that would be where
    the overflows leaked. The tank kept draining, and draining. When it was done there was no water in the tank. Both
    of the overflows leak at the bottom where they attach to the glass. The pressure of the water had pushed the acrylic
    away from the silicone. I had only put silicone on the outside.

    Sorry for the long story. I do have a question.

    How do I silicone the overflows in place?

  2. #2
    Senior Member tang_man_montreal's Avatar
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    I'm trying to understand your situation....

    -Do you have a glass tank with 2 corner overflows?
    -What thickness is the acrylic that you used for the overflow walls?
    -Are the overflow chambers square or triangle?
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

  3. #3
    Senior Member AndrewNS's Avatar
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    The tank is 90gal glass with 2 2" bulkheads in the bottom corners of the tank but on the back pane of glass. The acrylic for the two, two sided rectangular overflows is 1/8". The long side of the overflow is around 7-8" and the short side is 5-6".

    Here is a rough pic...

  4. #4
    Senior Member tang_man_montreal's Avatar
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    Hmm... I'm going to let others chime in here... but I would definately suggest using silicone on both sides. I'm also not sure if 1/8" is thick enough. You may have to step that up to 1/4".
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

  5. #5
    Senior Member ReefVan's Avatar
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    Agreed, the acrylic should be 1/4" to prevent bowing and excess flexing. As we all find out sooner or later, acrylic doesn't stick well to glass with silicone. :

    It is essential that the overflows be filled at the same rate as the tank to avoid excess pressure on the overflow walls. Try using a small siphon hose, this way as the tank fills so will the overflow.

    After all that's pretty thick glass holding the water back and to replace it with a thin piece of acrylic is looking for trouble.

    Understood that when the tank is full that the overflows see no great pressure differential, but there is one and acrylic tends to warp with time and water absorption. Glass doesn't...

    The other alternate is to use glass, which I will use on my 220, that way at least you can scrub it if you wish and it won't come loose or bend and crack.
    It's not junk, it's un-assembled DIY!

  6. #6
    Senior Member reefmutt's Avatar
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    I agree with Van that glass is the way to go. No matter how much silicone you use on acrylic, it will never adhere like it does to glass. You never know, somewhere down the road, when the glue has dried out a little, you knock the overflow or something and it dislodges and starts to leak. It would suck to have to tear down your 'great barrier reef' for a stupid overflow plate.
    Why not use glass overflows and glue your acrylic to the outside to hide the interior, or use smoked glass?
    I just think that there are so many possible things that can go wrong when setting up- this doesn't have to be one of them.
    Van, I have a concern with your suggestion of filling the overflow sections at the same time as the tank...By doing this you never get the opputunity to see it the overflows are really doing their job.
    Matt.

    Old system torn down to make a playroom.. planning a 62x42x28 high

  7. #7
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    OK ... from what I have been told (by a plastic shop employee) you need to use silicone "ADHESIVE" as compared to silicone sealer to join Plxi-Glass to glass. Trouble is that silicone "ADHESIVE" is not tank safe so use as little as possible to make that bond. When the adhesive is fully cured seal it in with the tank safe silicone sealer. And as has been said use 1/4 inch Plxi. Also scuff the plxi on the edge where the joint will be.
    Rob

  8. #8
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    I also don't use glass on over flows because you can't cut stock saver teeth into the top edge of glass. The first reef tank I did was a glass overflow and I did loose a few small fish that died in the strong current that is created at the bottom.
    Rob

  9. #9
    Senior Member ReefVan's Avatar
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    Matt,

    By filling the overflow at the same time as the tank you will see if the overflow is doing it's job... it's job is to handle the level diffential between the tank and the overflow chamber which can be anywhere from 1" to 3" in height.

    A differential of 20" to 30" is not what you'll see unless you plan on having Niagara Falls and the accompanying sound included in your set-up.

    Rob,

    Go to your local HD and pick up some plastic Rain Gutter guard plastic or egg-crate, this is what we bond on the top of a glass overflow to prevent our livestock from going over the edge........
    It's not junk, it's un-assembled DIY!

  10. #10
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    Yes that would work .. however I have plxi now with the outside corner folded so it looks as neat as is possible. teeth are cut into the top edge. Thanks ReefVan ... And Marry Christmas or Happy holidays
    Rob

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