DIY external overflow on 20" cube

[nerdz]

Hi

I just received a current USA 34G 20" cube super bright tank. Its basically a Solana minus AIO chamber.

I want to install an external overflow box, notched coast to coast style... Hoping some experts chime in.

Wondering about:

width of over flow?
2 pipes?
What diameter pipes, 3/4"?
Water height in tank, 1.5" down (rimless tank)?
Glass thickness, 3/8"?

I know that is a lot of questions, but any input would help.

Cheers!

[daniella3d]

I first went your route and did a home made external overflow but the security was not there so I ended up buying a gl******* small nano overflow and drilled the tank. That's peace of mind 100% safe.

At the end I spent as much money on making my external overflow with pipes than what cost me the nano overflow.

[nerdz]

Thanks for the input daniella3d.

Id like to avoid the gl*******s kit because l don't want anything inside the tank. Also, ld prefer 2 drain pipes, a throttled one and an emergency.

It will be glass construction so it will bond well with glass. I'll try and sketch my idea so other know what l have in mind.

Cheers

[lockrookie]

read my 50g thread...enjoy and good luck any questions pm me

[ScubaSteve]

Not sure I follow. Are you wanting to mod an existing tank? If so, notching a built tank for c2c overflow is risky business.

But, to answer your questions...


width of over flow? I can help you calculate this but I recommend 12" to be able to handle over 800gph (over engineer)

2 pipes? Go three and do a beananimal overflow. Use gate valves for tuning the pipes.

What diameter pipes, 3/4"? No, go with 1" if you can

Water height in tank, 1.5" down (rimless tank)? That is your preference. I have my water height 0.65" from the edge (rimless). But that is a 1.25" x 12" notch flowing 600+ gph. You need to account for the laye thickness of water flowing over the weir (again, I can help calculate this).

Glass thickness, 3/8"? Yup, that's plenty thick.

[nerdz]

read my 50g thread...enjoy and good luck any questions pm me


Thanks, yes this is more along the lines of what I had in mind... Congrats on your sweet build!

[nerdz]

Not sure I follow. Are you wanting to mod an existing tank? If so, notching a built tank for c2c overflow is risky business.

But, to answer your questions...


width of over flow? I can help you calculate this but I recommend 12" to be able to handle over 800gph (over engineer)

2 pipes? Go three and do a beananimal overflow. Use gate valves for tuning the pipes.

What diameter pipes, 3/4"? No, go with 1" if you can

Water height in tank, 1.5" down (rimless tank)? That is your preference. I have my water height 0.65" from the edge (rimless). But that is a 1.25" x 12" notch flowing 600+ gph. You need to account for the laye thickness of water flowing over the weir (again, I can help calculate this).

Glass thickness, 3/8"? Yup, that's plenty thick.

Thanks, yes planning on notching my brand new prebuilt tank. I don't plan to have flow over 300-400 gph. Okay, sounds like 1" pipes. Is this really necessary for this flowrate?

Cheers for the input!

[lockrookie]

Its better to have over kill than not..and easier to do now when empty than full. And in this case easier to shrink than make bigger.. You can always reduce your plumbing to a smaller diameter with your fittings but harder to redrill the holes in the glass bigger.

Just my .02

[nerdz]

Update.

I've decided to go with a beananimal system, using 1" piping. The overflow will be 12-14" wide and 1"deep. Weir height will be less then .25"

I'm thinking only 1 return line, any opinions? I'm going to be pushing 200-300gph.

Also, would 10" for the height of the overflow box be adequate?

http://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/34g.jpg

I'm going to cut notch with a diamond ring saw, (basically a little diamond round-bladed bandsaw which can cut in any direction).

Here is some helpful info from a fellow Canreefer ScubaSteve:

"So here we go...

To determine the height water above the edge of the overflow you treat the overflow as what is known as a contracted weir. Don't worry about the terminology, I just want you to know what it's called in case you wanted to look up the math. Basically, with a contracted weir, you need a given cross section to pass a certain volume of water every second. If you make the overflow very wide, the layer over the overflow is very thin. If you make the overflow narrow, the layer will be thick. For our aquariums we want the layer going over the edge to be as thin as possible for three reasons: 1) we want to skim off the surface film without taking too much clean water (makes the overflow waste more concentrated which makes the skimmer more efficient); 2) if you have a thick, fast flowing layer of water you will have critters going for daily sump rides (it will literally suck them over the edge); and 3) a thinner, less turbulent layer of water flowing over the overflow is be silent where a thick layer will sound like Niagra Falls. My tank is in my living room, so I opted for silence.

One thing you missed telling me is what kind of wavemaker you are planning on. All of them have slightly different wave patterns and wave heights. The thing with wave boxes is that they can make your overflow discontinuous. If we assume the wave travels left-to-right in your tank, and if you put your overflow at the side of your tank, it will only overflow when the water level at the side of the tank is flat or cresting above the overflow edge (so you'll end up with a ...Wooosh!...Whooosh!...Whooosh!... thing going on). If you put the overflow at the center back, and assuming you made it long enough, one half of the overflow will always be overflowing and be less "whooshy". If you want to run a wavemaker, take your wave height and add on 1" - 1.5" for good measure (so about 2" or more total distance from the tank lip to the overflow edge) and call 'er done.

If you hate the look of a mile of wasted glass above the water line like I do, I'd calculate it as a contracted weir but this won't allow for a wavemaker. To save you from doing math, you can use this: http://irrigation.wsu.edu/Content/Calculators/Water-Measurements/Rectangular-Contracted-Weir.php (http://irrigation.wsu.edu/Content/Calculators/Water-Measurements/Rectangular-Contracted-Weir.php). Find out your target overflow rate in gpm (so 300 gph is 5 gpm), enter in your overflow width and start tinkering with the weir height until the flow rate matches your target flow rate. That will be the height of the water over the edge of your overflow. Add 0.65" - 1" on top of this and that is how deep you need to cut your notch. So to give you an example:

I am going to assume here for a minute that you will have two returns into the tank, one placed on each side of the overflow using 1" PVC bulkheads. To make your life easy and to avoid cracking the glass you'll need about 3"-4" of room for the bulkheads (let's call it 4" for argument sake). So this leaves you with about 12" left of the original 20" to work with. So, you've got 12" center overflow and ~300gph of water flowing over the edge (5 gpm): that gives us roughly 0.25" of water flowing over the edge of the overflow. If you add 0.75" to that you have to cut a 1" notch that is 12" long. Using a 1" notch will give you a flow range of 300 to 480 gph. 480 gph will bring you about 0.65" from the edge of the tank which, in my opinion, is the minimum needed to avoid splashes. I use 0.65" and I only get splashes if I'm being super lazy and careless with the magfloat. I have a Hydor that pushes water right to the surface and creates a small standing wave on one side of the tank; it has never splashed.

Another consideration is how much excess water your tank can handle. If you leave 0.75" about the water surface that means your tank can handle an additional 1.25 gallons (plus whatever your overflow box can hold) before your tank ACTUALLY overflows in the off chance that all three of your overflow pipes go wacky and can't drain the water. So, when you design your sump if you have an overflow into the return pump section that limits the volume in that section of the sump to ~1.25 gallons, there is no physical way you'll ever flood your tank as the pump will run dry before the water can reach the edge of the tank. Combine that with the beananimal design and you've got a solid system that won't ever flood your house unless something catastrophic happens to the tank.

One final note: Do try to calculate your actual return flow rate. It will make your life much easier and avoid the "Oh #@%*, I just flooded my floor" scenario. There are a number of good calculators out there for this and some built specifically for aquariums. I recommend this one: "

[nerdz]

http://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/2012-09-06205420.jpg














http://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/2012-09-06205130.jpghttp://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/2012-09-06205429.jpg



Just a quick test with ring saw... I will use a guide for bettter cut. I also have a diamond grinder to smooth edge after ringsaw.

[ScubaSteve]

http://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/2012-09-06205420.jpg














http://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/2012-09-06205130.jpghttp://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/2012-09-06205429.jpg



Just a quick test with ring saw... I will use a guide for bettter cut. I also have a diamond grinder to smooth edge after ringsaw.
Looks about right. Use lots of cooling to avoid overheating the glass and cracking it. Cut at a moderate pace but take breaks if you can to avoid overheating.

When. You say 0.25" weir height, you are referring to The water layer thickness over the weir, correct?

[nerdz]

"You say 0.25" weir height, you are referring to The water layer thickness over the weir, correct?"

Thats right, so my 1" notch in tank will result in a waterline of 1" -.25",(actually less then .25" at my flowrate...), so .75" down from top edge.

Ya, it doesn't get warm and I'l flood it with water. The saw is intended to be used like a bandsaw. Flat glass is slid on its table into the blade. I took it apart so I can use it on my already assembled tank. It'll be like a skil-saw!

Normally its feeds water from the bottom of the table, but in its Franken-state, I'll use a garden hose.

Cheers

[nerdz]

Well, notched tank for overflow... Went pretty well/fast.


Now for return line. Need a diamond bit to drill for .5" bulkhead. 1 or 2 returns? I'm thinking 1.


I painted the back of my last tank, what can I do to hide overflow box and stand pipes? Ideas would be appreciated!

http://i921.photobucket.com/albums/ad56/rawwilly/A%20few%20updates/reef/34gnotch.jpg

[toytech]

nice job , i just did this yesterday with a dremel , way easier than it looks. Got to love external overflows such a clean look .