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Thread: The Overflow

  1. #1
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    The Overflow

    I post this information in response to those who want more detailed information about the various parts of a well equipped reef aquarium. I will post on other topics related to setup in the future

    THE OVERFLOW
    The “overflow” part of your setup is the part that allows you to remove water from the display aquarium and deliver that water to the sump (see THE SUMP ). An overflow setup is required to run a sump system.
    The overflows job is to allow water in the display aquarium to flow freely to the sump in a controlled fashion. The overflow also controls the water level in the display aquarium. The overflow, by the way it is set up, also removes surface scum from the display aquariums water. This allows for improved gas exchange across the aquariums entire water surface. Good gas exchange is desirable.
    To make an overflow there are 2 common approaches.
    The first and most common approach is to drill a hole in one of the accessible back bottom corners of the display aquarium. This hole will accept a 1.5 inch or larger water tight bulkhead fitting. To the underside of this bulkhead fitting is attached a pipe or hose that leads to the sump by way of the shortest possible distance. To the top side of this same bulkhead fitting is attached a stand pipe (see THE STANDPIPE )
    In the same corner of the aquarium where this bulkhead fitting is installed there is a 2 sided acrylic wall in the shape of an “L”. This wall is glued with aquarium safe silicone sealer to the side, back and bottom panes of the display aquarium. Once glued in place this wall creates a 4 sided water tight chamber within the aquarium. It is of the up most importance that this chamber be WATER TIGHT.
    The dimensions of this chamber will be about 6 or 7 inches square. This wall will be the same height as the display aquarium when measured from the bottom pane of the aquarium to the underside of the top plastic trim. Into the top edge of this “L” shaped wall there will be slots cut to create teeth. These slots that create the teeth are usually about 1 inch deep and spaced about 3/8 to ½ an inch apart. The slots themselves are about ¼ of an inch wide. The job of these teeth is to keep your fish and other livestock from going over the wall and into the sump. They do the same job as the steel grates that cover storm drains on your street. Water flows through and you don’t. Cut the slots BEFORE installing the wall!!
    The second approach is to skip the internal wall and drill the hole into the back of the aquarium (very useful when the bottom pane is tempered). Into this hole is installed the water tight bulkhead fitting. To the backside of this bulkhead fitting is attached a sideways “T” fitting. To the bottom of the “T” fitting is attached a pipe or hose that leads to the sump. To the top of the “T” fitting is attached a pipe that adds height to the top of the “T” so the top of the “T” is extended ABOVE the display aquariums high water line. To the inside of this same bulkhead fitting is attached a 90 degree elbow with a reversed reducer that creates a circular overflow basket. Into the top edge of this circular overflow basket create the same teeth as would be used on an internal overflow wall. That’s your basic overflows. See the pics to better understand the concepts.
    How dose it work ….
    When water is pumped into the display aquarium from the sump the water level in the aquarium rises until that water flows through the teeth in the top of the overflow wall or basket. From there this water flows through the hole in the aquarium and back to the sump. The sump contains enough water to not be emptied by the pump. The sump MUST also have a reserve capacity big enough to handle all the water from the aquarium that is above the bottom of the overflow walls teeth when the system is running. If the sump dose not have this reserve capacity water from the aquarium will overflow the sump during power or pump outages.
    Starting the system usually involves …
    1) Filling the display aquarium to the bottom of the overflow walls teeth.
    2) Filling the sump to about 4 inches below it maximum capacity.
    3) Starting the sumps return pump.
    Once the system is running you will see that about 30% to 50% of the sumps water (depending on the size of the display aquarium and the size of the sump) must be displaced into the display aquarium to get water in the display aquarium to start flowing over the wall or basket and back to the sump. Never top up the sump after the setup is running. During a power or pump failure all that displaced water that is temporally in the display aquarium will return to the sump.
    Hope this is helpfull... Hope I didn't forget anything.
    Rob

  2. #2
    Senior Member pwall's Avatar
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    Once again OSD, excellent post.
    Regards,
    Patrick.
    Ottawa (Orleans), Ontario
    Yahoo IM: pwallnfld

  3. #3
    Senior Member hippo!'s Avatar
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    Keep em commin' OSD!

  4. #4
    Senior Member tang_man_montreal's Avatar
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    OSD,
    I've been adding hyperlinks to the other posts within these posts to make easier for everyone.
    I am Homer of BORG... Prepare to be..OOOO!! DONUT!!!!!!

  5. #5
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    Thanks Vince ... thats a good idea and very helpful for all who read this stuff.
    Rob

  6. #6
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    I'm up grading my reef tank fro a 65gal with no sump or over flow to a 90gal inwall with a sump. This is my first time and need some help. it seems that my over flow is to slow for my 600gal/Hr pump. the hole that i got drilled is 2' 1/4 and the abs pipe is 1' 1/2. How fast should the pump be? Because i was scared that 600g/h would be to slow!

  7. #7
    Senior Member pwall's Avatar
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    600gph should be fine. What kind of pump is it?
    And what size is the return line ?
    Regards,
    Patrick.
    Ottawa (Orleans), Ontario
    Yahoo IM: pwallnfld

  8. #8
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    Do I understand your question correctly? You are concerned that a 600 gallon per hour pump will not move enough water through the sump on your 90 gallon tank?
    If this is correct the maximum flow through the sump for a 90 gallon display tank would be 900 gallons per hour. A 1.5 drain should be able to handle that much volume. If your pump is 600 GPH your still within the 5 to 10 times recommended turn over rate of a 90 gallon tank. 450 GPH would be the minimum pump size to use on a 90 gallon tank
    Rob
    Rob

  9. #9
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    thankyou very much. the pump that I'm running is an old ehiem. The proble was in my pluming design. I tried to do some fancy work outside the tank to correct my water level. but theory doesn't allways work as well as planed. so I'm tacking it all apart and starting over.Soooo fustrating!!! :grr: thank you again for the advice and i'm going to stick to the original plan.

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