How Exactly Does A Sump Work?

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TheFishBoss

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Jan 23, 2013
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to the best of my understanding, it's a separate tank below the display tank that has a gravity fed hose going down to it, and a pump powered hose going back up to the display tank, and it is for putting filters, water heating equipment thermometers, and testing equipment in it. it is connected to the main tank by holes drilled in the tank, and is sealed with something (i'd like to know what this is sealed with). is that basically correct? can you use a basic 20 gallon fish tank for your sump? if i buy heaters for my 50 gallon tank and a 20 gallon sump, i'd need a 70 gallon heater, right? thanks.
 

SubRosa

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Jul 3, 2009
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Yup, that about answers it.
 

Bushkill

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Dec 1, 2011
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That's it in a nutshell. Another benefit is just adding more water volume to the overall system, as well as more surface area for gas exchange to occur. Also in a SW system, it lets you install bigger and more efficient protein skimmers that can only be operated in a sump.

The sealant used is the same used on aquariums. Silicone. The GE sealants are sealants. They may save you a few dollars per tube, but don't have the tensile or adhesive strength aquarium silicone does. Not all "silicones" are created equal, but for baffles, the GE sealant usually does well. And NO silicone does not adhere to acrylic well over the long term.

Glass sumps do require some careful handling. They are glass, and a slip of the return pump or a whack while moving the heater can cause issues if not a catastrophe; hence many are made from acrylic which is a little more forgiving of clumsy handling inside.
 

OrionGirl

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Which part are you saying is sealed? The holes? That isn't sealant, a bulkhead is used to seal the opening around the plumbing.
 

Khemul

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Oct 14, 2010
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Glass sumps do require some careful handling. They are glass, and a slip of the return pump or a whack while moving the heater can cause issues if not a catastrophe; hence many are made from acrylic which is a little more forgiving of clumsy handling inside.
Glass sumps are really not worse then regular fish tanks when it comes to equipment accidents (with good reason... ;)). It isn't so much about fragility for why acrylic is often used. Acrylic is great from an industrial and commercial standpoint. And the nature of the sump eliminates most the disadvantages while maximizing the advantages. It's light-weight. Suddenly no one cares if it scratches easily. Holes can be drilled whenever and wherever needed. Panels can be molded into various shapes and designs. Plus from a commercial standpoint, glass sumps look like something anyone with the ability to prop glass panels up long enough for silicone to seal could do (which is basically true). Acrylic on the other hand has the fancy molded look that makes many believe they can't do it themselves.

You see many glass sumps on the DIY end of things, since they are perfectly fine as long as you treat them like they are made of glass (which is basically the same as you would treat any glass aquarium really).
 

Khemul

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Oct 14, 2010
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You don't. It is basically impossible to balance two pumps perfectly since pumps don't run at a constant speed over time. It is more of a descending slope that goes lower and lower the longer maintenance is not done. And the slope will depend heavily on factors that you can't control.

The return pump sets the flow, assuming the drain can handle it. Gravity handles the balancing act. If you did the plumbing right then water flows to the sump at the rate of the return pump. If you did the plumbing wrong then water flows to the floor at the rate of the return pump, minus the capacity of the plumbing... :evil_lol:
 

greech

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May 13, 2009
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On a drilled tank that isn't that important for the exchange of water to happen. As long as the return is strong enough to pump water back up into the tank, gravity will handle the rest. You can have a pump that is too large for the drain(s) to handle. However, that is easily solved with a ball or gate valve installed in the return line (after the pump's output) to throttle back the return rate. The valve will not harm the pump at all. Some people put valves on their drains instead which is an unnecessary risk when the same can be accomplished by placing the valve in the return line.

Another misconception is that a return pump must match the drain capacity of a HOB overflow box. A 700 gph overflow means it will handle up to that amount (although most HOB flow capacities are overrated). When using a "U" tube HOB box, you do have to move enough water through the "U" so that it remains full of water and air bubbles don't collect at the top. That can lead to a siphon break and a flood. Again, this is easily solved by using a larger return pump than the HOB is rated for and adjusting the return flow with a valve in that line. Weir style HOB overflows (CPR, etc) use a air pump to maintain a siphon and do not have the same issue. However, I would trust a properly installed "U" style box over a weir. If the air pump fails or doesn't restart after a power outage, you will have a flood.

Probably more than you wanted :)
 
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