Does Anyone Know How Water Levels Work With An Overhead Sump?

[fishwarrior]

Normally, the Display Tank is on top and filled up and the sump below is only filled partially.  Now with a sump on top over the display tank when the power is turned off does the water in the overhead sump get drained into the display tank, if so then it would flood.  Does it work differently with an overhead sump?
 

 

[fishwarrior]

I read somewhere that an overhead sump acts more like a normal overhead filter and an overflow is not necessary since it drains back into the display tank?

 

[Ginger726]

I'm not sure exactly but I am searching the forum to find out basically the same thing.  I think the refugium is a wonderful filter but it does worry me a little.  I think the overhead above may overflow the display tank and the sump below may siphon out the display tank.  I hope some of the pros can help explain so I can set up a great system on my 125 Gallon

 

[misterpro]

Logically (to me) a overhead sump only drains water that goes higher than a certain level (in the sump) so a powercut would just stop the water flow, without raising the water in your tank (alot).  At least that's what sounds normal to me, I'd consider other behaviour a design flaw.
 
I don't have experience with overhead sumps so this is just my best guess really.  Basically I don't see how anyone would even want to consider using them if having a power-cut would mean you'd automatically flood your tank...

 

[TwoTankAmin]

Basically a sump works by a combination of gravity and a pump. In an under tank sump gravity remove the water from the main tank and the pump in the sump returns it to the tank. An overhead sump works the other way. You need a pump in the tank to get the water up into the sump and then gravity is what returns it to the tank.
 
There are several ways to make the system more fail safe to prevent flooding. This normally involves some form of float valve. This works like your toilet when flushed. The refill water is turned on and off by that floating ball in the water tank part of the toilet. The float valve in a sump system is used to turn off the pump at a given level. And  instead of being entirely mechanical only like your toilet, a float valve can control and on/off switch for the power to the pump.
 
The float valve can work in either direction. That is, it can be used to turn on or off if the water rises to a specified level or if it drops below a certain level.
 
The way a sump works to protect one from flooding during a power loss has to do with the overflow part of the system that runs on gravity. Basically water is able to flow into, thru and out of the overflow as long as the water level is higher than the overflow intake. If the water drops below this level, the flow stops. Think of it like you do a siphon used for a water change, if the intake of the siphon is fixed two inches below the surface of the water, when the water has dropped two inches, the flow stops because the siphon is broken.
 
It is the combination of the float valve on the pump and the level at which one sets the intake of the overflow part which prevents flooding.
 
Here is a vid on how to build a  DIY overhead sump http/www.youtube.com/watch?v=YFcioRUCa6c

 

[fishwarrior]

On my current bottom sump, I don't use any float valve, it's pretty stable without one.   The thing with the overhead sump videos including Joeys is they don't explain the water level part and how it works when the power goes out.  I've heard some people say it would act as a regular power filter and no need to worry about overflow and other people saying it's a flood waiting to happen.  I guess I'll just have to test it and see how it works.  I was planning on using my overflow box as the return but not sure how that would work if the overhead sump would acts as a regular sump.
 

Basically a sump works by a combination of gravity and a pump. In an under tank sump gravity remove the water from the main tank and the pump in the sump returns it to the tank. An overhead sump works the other way. You need a pump in the tank to get the water up into the sump and then gravity is what returns it to the tank.
 
There are several ways to make the system more fail safe to prevent flooding. This normally involves some form of float valve. This works like your toilet when flushed. The refill water is turned on and off by that floating ball in the water tank part of the toilet. The float valve in a sump system is used to turn off the pump at a given level. And  instead of being entirely mechanical only like your toilet, a float valve can control and on/off switch for the power to the pump.
 
The float valve can work in either direction. That is, it can be used to turn on or off if the water rises to a specified level or if it drops below a certain level.
 
The way a sump works to protect one from flooding during a power loss has to do with the overflow part of the system that runs on gravity. Basically water is able to flow into, thru and out of the overflow as long as the water level is higher than the overflow intake. If the water drops below this level, the flow stops. Think of it like you do a siphon used for a water change, if the intake of the siphon is fixed two inches below the surface of the water, when the water has dropped two inches, the flow stops because the siphon is broken.
 
It is the combination of the float valve on the pump and the level at which one sets the intake of the overflow part which prevents flooding.
 
Here is a vid on how to build a  DIY overhead sump http/www.youtube.com/watch?v=YFcioRUCa6c