out box... half inch?

[Hawaiianfishkee]

sup guys. this is like my third thread today.. sorry for the hassel. amyways, my friend gave me an acrylic sump( about 10 gal), and an outer over flow box. im planning on using it for my 55 gallon tank that i plan on making SW.. before this i had a diy overflow system running with one 1" U tube and 2 1 inch drainage pipes. i built the out box with 1 1" drainpipe but the system couldnt handle the pump, so i added a second 1" drain pipe and the system worked perfectly. i noticed that the out box that my friend gave me has like a 1/2-3/4" drain pipe!/ but larger in hieght and divided into two chambers (u tube chamber that drains into drainage chamber). di you think this overflow will handle the 250 gallon pump?
i provided i picture of how the out box looks on the right side... thanks in advance

 

[Pharaoh]

1/2" will flow about 150gph
3/4" will flow about 330gph

You will be restricted by the diameter of the PVC

 

[Toby_H]

If two bodies of water are connected by a siphon created with a ½” hose…

And both bodies of water have a surface level at the exact same elevation…

There will be 0 flow in the siphon…

If the surface of one body is at all higher than the other, water will flow through the siphon in attempts to seek equilibrium…

Are you suggesting the maximum flow through a ½” hose will be 150 gph… That I could believe…

But the greater the difference in elevation, the faster the water will flow…

This overflow box will not create nearly enough of a difference in elevation for the maximum flow rate of the siphon to take place… Therefore I suggest that a ½” hose will actually function at much less than 150 gph with slight variations in elevation…

I suggest using multiple U tubes of as large of a diameter as possible…

 

[Pharaoh]

Providing the information on the same theories that are used in the DIY overflows. Maximum flow rate through 1/2" would be 150gph.

 

[Toby_H]

Gotcha...

But it should be noted that there are details that may prevent it from functioning at "maximum capacity"...

Since this is two bodies of water with very similar elevations being connected by a siphon...

Where in an overflow all the way down to a sump type situation it is a siphon connecting two bodies of water that have several feet difference in elevation...


To verify what I am talking about...

Start a siphon with a hose out of your tank into a bucket... hold the hose about 2" below the tanks surface... water slowly flows out...

Now lower the hose a few feet... the water is coming out much faster isn't it?

Therefore... the elevation between the two bodies of water connected by a hose... as well as the diameter of the hose... dictate the speed the water passes through the hose...


neglecting to acknowledge the elevation is ignoring a major influence... such oversights can cause fee tto get wet

 

[Pharaoh]

The real question that should be asked is the inner diameter of the the U-tube that connects the overflow to the tank. The OP stated that the drain line was 1/2"-3/4". Without regard to the U-tube, this would give the system the ability to flow 150-330gph in gravitational flow. There might be a limiting factor based on the size of the U-tube, but with this size an unknown part of the equation, we would not be able to know what the overflow will actually flow.

Typical U-tube sizing for overflow boxes is a 1 1/4" OD tube. The assumption could be made that the inner diameter would be no more than 1 1/8". With twin U-tubes, the overflows are rated for 1,200gph, give or take a few gph for the additional 1/8".

The differences between gravitational flow and horizontal flow are minimal with such a small length in consideration. I would argue that the loss in flow rates would be minimal as many of these setups work well when pushed to the limit. I have seen quite a few single tube overflow boxes run on tanks using Quiet One 4000 pumps at just under 6' of head height that flow well.

 

[Toby_H]

Ahhh... I'm a little clearer now...

So there are two points that could limit this overflow box...

The drain out of the exterior box... as well as the U tube...

and whichever one can handle less is the limitation of the overflow box as a whole...


I've never measured the flow rate... but I would suspect with several feet of drop a siphon with a 1/2" hose/pipe would flow at more than 150 gph... but I'm not sure about that...

I've seen several charts that list flow rates for different diameter hoses... but I've yet to see one attached to an article that thoroughly explains the considtions in which it flows as such. I'm sure on eis out there, I've just yet to see it...


I've done a lot with aquarium plumbing, but I've never used an external overflow box though... it just seems like there are too many points something could go wrong...

 

[Hawaiianfishkee]

Wow.... That's a lot more numbers than I was looking for. Yah I figured it wouldn't be enough flow. Ima try it out anyways. Maybe i will drill I a wider hole the outbox so it alow more water to drain. Thanks guys. Keep the info coming.

 

[Pharaoh]

Can you tell us what the inner diameter of the u-tube is? If it is smaller, it will reduce the flow.

 

[Hawaiianfishkee]

ok so i thought i'd take some pics so you guys would get the jist a lil more...

this is the diy overflow i made from those hanging fish keepers that you always see in the pets shops.... krylon fusion

this is the old diy out box that i used to use... notice the 2 1" drain pipes

both the overflow box and the out box held a syphon using a 1 1/4 U tube (i measured it today)


this is the new out box that i recieved from my friend.. i thought i would run some tests...

the water level was rising higher than the overflow box holes! i adjusted it so that the overflow box was higher than the black divider in the out box... i also made sure the U tube had enough space to allow full water flow... the water level in makeshift tank stayed at overflow level but then my out box wasn't draining fast enough and water level started to rise... at the same time the makeshift sump was running low on water and pump was sucking dry...

maybe because?

there's a 1/2" drain hole in bulkhead

should i drill this wider and put a bulk head with like a 1.5" hole?

remember my old out box had 2 1" drain pipes... if i drill the drainage hole wider... will the overflow system keep up with the pump?


any more advice guys? thanks folks