Internal overflow size

[SalmonAlley]

I've got a 180g with two 2" bulkhead drilled about 3" from each other on the back glass.

I'd like to build a simple internal overflow box to over these bulkheads. From a flow-rate standpoint. I plan to use an AM3000 which should end up returning water at a rate of roughly 2000 gph, and I'll probably have a second pump to feed the refugiums which might return water at around 500 gph. So we're looking at 2500 gph total flow through the 2" overflows.

1- Will the dual 2" overflows be able to handle this?

2- How large of an internal overflow box (dimensions of box and width and depth of the teeth) would I need?

Much appreciated.
SA

 

[handyman]

Great question I want to know the same exact thing, I'm haveing a 150g built right now with 1 2" overflow and I'd like to know what size teeth to have made

 

[SalmonAlley]

Handyman-

I did some research...there is a drain pipe size calculator on reefcentral which also provides "minimum linear overflow size"....not sure what exactly that means...BUT a single 2" bulkhead can handle almost 2500gph...

Any idea what they mean by that linear overflow size?

 

[handyman]

don't know but I'll figure it out and let you know

 

[handyman]

my guess is, the surface area need to feed that amount of water “spaces in between the teeth” if thats the case I'm in trouble

 

[SalmonAlley]

That's what I originally thought, but that doesn't seem right. That would mean for a single 2" overflow, pushing 2350 gph, you would need a linear overflow of 35". If you figure the spaces between the teeth are typically 0.25", then you would need 140 of these spaces. Figure a 0.5" 'tooth' in between each space and that's 105" of overflow box!

That means a box which comes out 21" off the back wall and travels 63" down the tank!! That IS a tank! and that's just to feed ONE 2" bulkhead.

We must be misinterpreting what it means...

Maybe someone else can jump in here and explain this to us.

 

[ChrisRD]

Hey Guys,

I haven't had a chance to check out the calculator you're talking about, but a quick search turned this up. Might be helpful.

http://reefs.org/phpBB2/viewtopic.php?t=8564&highlight=overflow+capacity

You could also measure the overflows in reef-ready tanks by companies like Oceanic and AGA and contact them to find out what that overflow is rated for. Might give you a starting point for guesstimation...

 

[SalmonAlley]

Thanks! Great link!

 

[kycoralhead]

Greetings
I have built a couple of pond filters and used 2" bulkheads for 1800 gph. I only used one and it carried the flow. You may have to get away from the idea of teeth and maybe use some plastic mesh to keep stuff out of the overflow. You did not say where the holes were. Are they near the top or on the bottom? You also may have to calculate how much water will flow over the top of the box. In my filters the water level rises about an inch above the box from a 1800 gph pump. You could build your box so you could adjust it to allow for whatever size pump used. The height in the tank will determine how much water flows to the sump when the power is shut off. This is important too. Dual 2" pipes will carry a lot of water. The guy using the 1.5 inch pipe will be limited as the 2" pipe will carry almost twice as much water as the 1.5" pipe. I know it does not seem right but thats the way it works. Good luck