# Quick question regarding sump setup



## SBCam (Apr 25, 2010)

Hey all, I have a quick question regarding setting up a sump, as I am about to set one up for the first time. I bought a used overflow box, plumbing, pump and sump box, so I have all the equipment needed. The thing I am having problems understanding before I start setting it all up, is if gravity basically feeds the sump down from the overflow box, and a pump sends it back up to the tank, how is it that the gravity flow is the same as the pump going back up? I mean, if the pump is to strong, wouldnt it continueously run the sump dry? or if the gravity feed was stronger than the pump, wouldnt the box fill up more than you want, and continuously dry out the overflow box?

Also, how do you go about priming the lines? Or do you not need to prime the lines once you have everything set up? Any answers for these newb questions would be greatly appreciated.. thanks!


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## davej (Apr 28, 2010)

The important thing is that the overflow is able to handle a greater flow than the pump can deliver. If all is right You want the sump to be full enough above your return so that when the pump turns on and delivers the water upstairs to the tank it doesn't run dry. But you also want to consider that if your power goes out that all the water that drains down doesnt overflow the sump. 
So now when you turn on the pump the waterlevel will rise in your tank, with the only place to go being over the lip of your overflow box and back down into the sump. If your pump were minuscule and only pumped one gallon an hour that one gallon would go over the edge and replenish the one gallon pumped out.
Make sense?
As was stated earlier the only two ways to get in trouble is to have too large a pump for your overflow box to handle, thus pumping the entire contents of the sump up into the tank and possibly overflowing it. The other problem that could arise is doing a water change with the pump running and filling your sump right up. In this situation all will be fine until you/power outage turns off the pump and the water all drains down into the sump overflowing it.


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## fkshiu (Apr 22, 2010)

Davej is pretty much bang on in terms of do's and don't's.

I'll try to approach the concept of a sump system from another angle. Imagine you have a bucket of water full to the brim. Now imagine you slowly pour in a 250mL glass of water. How much water overflows out of the bucket and at what rate? That's right: 250 mL as slowly as you poured the glass in. Now imagine you quickly dump a gallon of water into the same bucket. How much water overflows and at what rate does it overflow now? That's right: 1 gallon as quickly as you dumped it in. 

That's how a sump system works. It has nothing to do with the common misconception of "matching flow". The display tank will only overflow as much water as is being pumped into it by the return pump. Therefore, as Davej pointed out, the question is whether your overflow box can handle what the return pump dishes out.

And, as Davej indicated, the other major issue is what happens during a power outage. Thus, you must ensure there's enough empty space in the sump to handle the backflow. You minimize backflow by placing your return outlet right at the surface of your display tank thereby breaking the siphon as soon as the water level begins dropping in the display.

Have a look at my sticky at the top of this sub-forum for more on sumps and how the work.


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## gklaw (May 31, 2010)

Your siphon size and the difference in level in your tank and the wwir inside the overflow box contol how much water your siphon can draw water out by gravity. 

As noted by Davej, you don't want too strong a return pump so that your siphon cannot keep up. You also don't want too small a return pump or you don't have enough flow in your siphon ending up with air trap and your tank will overflow again.

I went with a somewhat larger pump and put a valve at the output to the tank so I can adjust the return rate. You really need to place with it to get the balance.

To prime the siphon, stick an airlien into the sippon slightly pass the top and suck the air out with your mouth. The water will start flowing and you will have to cock the airline quick so no air can be suck back into the siphon. A couple of practice and you will have that master - I suppose you can also use a power air intake to suck the air out. I've suckign the air out manually for over 12 years


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## SBCam (Apr 25, 2010)

Thanks for the input, its starting to become a little more clear. The thought that the return pump is actually filling the water so that it can go into the overflow is still a little tough to get my head around. Thanks again, Im sure Ill have more questions once I attempt to set it all up lol


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## gklaw (May 31, 2010)

It is really no different than siphoning water out of your tank to drain. The only difference is:
- the tank is continuously being filled with water from the sump,
- if water go in faster than it can come out, the tank will overflow


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## lampshade (May 1, 2010)

The advice is great, when you shut off your pump your tank will only drain to the top of the overflow. Once you start up your pump it fills the tank and the water can fall down the overflow again.

The next fun part will be "how do i stop that gurgle" but that's for another time


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## tang daddy (Apr 21, 2010)

Typically if the return pump line is 1 inch the overflow drain is larger like 1.5 inch, overflow boxes do work but I always drill my tanks just incase of the fear of the overflow losing siphon... 

I am not trying to scare you but I just don't want to take the chance. For a sump some run a 20g sump on a 150 g display, the problem with this is as the water fills all the plumbing the sump will be drained close to 1/3 and then the water filling the display before it is able to overflow to the drain the sump will be drained to more than half. When this happens you have alot of water flowing through the sump creating micro bubbles in the display, that is why I recommend that the sump be 1/3 the volume of the display. That wAy when the system is completely off and the sump is full the sump will be 80% full making it so there is no bubbles in the display, another important thing to remember is when plumbing the return line which the return pump is on make sure that the nossel at the end of the return line just hits the surface of the display when the system is off.

The reason is because when the water is filled in the return line and the power cuts off it creates a siphon and will siphon as much as the line is submerged... So if the line is at the surface it immediately breaks the siphon but if it's 2 inches under that means it will back siphon 2 inches of water from your display back down to the sump and that's why I like to have the biggest sumps possible!!

Hope this helps...


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## SBCam (Apr 25, 2010)

Ahh thanks Chris, I hadn't thought of the overflow box possibly losing siphon, creating the tank display tank to overflow. If you have a barrier half way up in the sump, before going into the pump feeding back into the tank, and adjust the water level in the sump so that it is only say a half an inch above that barrier, as long as you dont keep your display tank completely full, it should prevent it from overflowing right? Or am I missing something... lol


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## Chewie (Jul 21, 2010)

*Overflow*

What overflow box are you using? I have a cpr 90. I purchased an aqua lifter pump to attach to it( About $20 @ JL Aquatics) . The purpose of the Aqua lifter is to restart the siphon if power goes out. Good luck on the sump

Hey I am working in South surrey. If you want a quick hand just pm me your number and I can come help if you want.


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## MadgicBug (Apr 22, 2010)

I have a cpr as well and found the Aqualifter better than using a powerhead for suction.

There is a thread in the form somewhere about using different type of return that doesn't require any suction. Can't remember what it was called, but I'm sure someone will chime in.


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