Can anyone here calculate overflow size?

[d2mini]

Hi, I need some help. Math and engineering is definitely NOT my forte. ;)

I'm having a rimless cube built and I need to figure out what size overflow and what size "teeth" cut into the top. It's a center column overflow in a 36" x 36" x 24" and I need to run a 1200gph pump. 3 holes will be drilled in the base of the tank inside the overflow for two 1" pipes and one 1.5" pipe. Just to have enough room for the bulkhead holes I'm figuring I need at least 6", but I have no idea how to calculate size for flow.

Help please! Thanks! :)

[skanderson]

the easy way to do it is to use the calculator in reef central. just type in what flow you want and it will give you the linear dimension you need to obtain that flow. be sure to give room for the standpipes. i would suggest one inflow and 2 out so you can make a silent overflow.

[mfinn]

http://www.reefcentral.com/calc/drain.php




http://www.reefcentral.com/calc/hlc2.php

[d2mini]

<a href=showthread.php?s=&postid=15571377#post15571377 target=_blank>Originally posted</a> by skanderson
i would suggest one inflow and 2 out so you can make a silent overflow.

Hi, I'm not sure what you mean by this. Do you mean two drain pipes? Because I was thinking of having a second one as an emergency drain.

The reef calculator for the drain pipe says I should have a 1.5" drain which is what I was planning on doing. But does the size of the overflow box matter?

Thanks!

[2_zoa]

<a href=showthread.php?s=&postid=15571703#post15571703 target=_blank>Originally posted</a> by d2mini
Hi, I'm not sure what you mean by this. Do you mean two drain pipes? Because I was thinking of having a second one as an emergency drain.

The reef calculator for the drain pipe says I should have a 1.5" drain which is what I was planning on doing. But does the size of the overflow box matter?

Thanks!

For proper surface skimming it does. I also think it is not best to drill to close together.

[d2mini]

Ok, so the calculator says....

Gallons per Hour = 1200
Drain and Overflow sizes are calculated as

Recommended minimum drain pipe diameter = 1.43 inches
Recommended minimum linear overflow size = 18 inches

So does that mean my overflow box needs to be at least 4.5" x 4.5"?
I know it will have to be bigger than that to fit the holes and bulkheads and have them spaced correctly, so I should be good to go, right?

What's the recommended spacing between holes?

[Plan>B]

Long read but IMO the best

http://reefcentral.com/forums/showthread.php?s=&threadid=1310585&perpage=25&pagenumber=1

[das75]

believe linear overflow size means just a straight lip, no notches.

As for hole placement, see often stay the hole diameter away from the next hole or edge.

[uncleof6]

das75 is correct. if you use teeth, the figure needs to be doubled or better depending on the width of the teeth, and the width of the notches. Also using teeth decreases the skimming efficiency of the overflow.

Jim

[d2mini]

So do you think it would be better to put teeth on the dursos instead of the overflow, like beananimal does?

[das75]

Attached to the top of my overflow is egg-crating, seems to work.

http://i67.photobucket.com/albums/h316/das75/EC_guard.jpg

[2_zoa]

<a href=showthread.php?s=&postid=15573345#post15573345 target=_blank>Originally posted</a> by d2mini
So do you think it would be better to put teeth on the dursos instead of the overflow, like beananimal does?

I asked beananimal about the teeth on his inlet. He told me that it has since been changed. He doesn't use teeth anymore.

[Plan>B]

<a href=showthread.php?s=&postid=15574477#post15574477 target=_blank>Originally posted</a> by 2_zoa
I asked beananimal about the teeth on his inlet. He told me that it has since been changed. He doesn't use teeth anymore.

Good to know.... Tanx 2_zoa

[d2mini]

Really? So no teeth anywhere?

What purpose do the teeth on the overflow really serve anyway, besides giving a place for algae to collect?

[uncleof6]

Teeth are to keep fish in the tank, unfortunately, they don't keep jumpers in anything. And the jumpers are the problem.

Jim

[d2mini]

So if I go with teeth, is there a certain size/pattern that gives the most flow?

That eggcrate screen looks interesting too.

[2_zoa]

<a href=showthread.php?s=&postid=15576753#post15576753 target=_blank>Originally posted</a> by d2mini
So if I go with teeth, is there a certain size/pattern that gives the most flow?

That eggcrate screen looks interesting too.

If you go with teeth just make sure that the throat of the teeth distance makes up the distance of linear OF needed. Throat being the valley. If you use 1 inch teeth then you will need to make it twice as long.

If you went with a calflow style you would have the very best surface skimming.

I should note, there is a limit on this. It would not make much sense in making 1 inch teeth. You may as well not have any. On the flip side, the smaller they are the less flow you will have through them and they will need to be taller as to accomidate the back pressure created by the narrow width.

[uncleof6]

Teeth, me thinks are in the waning twilight of popularity..... as is the full height corner overflow and variations thereof. High performance can have many meanings, however teeth, corner overflows and obsolete drain systems are definitely not high performance.

Jim

[d2mini]

I guess if the teeth were evenly spaced (the valleys being the same width as the high parts) you would need twice the distance no matter what their size is, right? What about height of the teeth? Does that make a difference?

[d2mini]

<a href=showthread.php?s=&postid=15577137#post15577137 target=_blank>Originally posted</a> by uncleof6
Teeth, me thinks are in the waning twilight of popularity..... as is the full height corner overflow and variations thereof. High performance can have many meanings, however teeth, corner overflows and obsolete drain systems are definitely not high performance.

Jim

So for a center column overflow, what do you suggest? I don't care what's popular or what's not. I'm looking for the best solution, period.

[das75]

Don't think you'll go wrong with a straight lip. Easy to retro-fit later if you think you need to with egg-crating just siliconed to the top.

Will say though, mine came with egg-crating and still the clowns will make it in the overflow.

For interest, this link (http://www.oceansmotions.com/forum/viewtopic.php?t=1129) shows a dual ctr column overflows with notches.

[uncleof6]

<a href=showthread.php?s=&postid=15577195#post15577195 target=_blank>Originally posted</a> by d2mini
So for a center column overflow, what do you suggest? I don't care what's popular or what's not. I'm looking for the best solution, period.

For a center overflow as much linear distance as practicality allows, and as much space for plumbing as you can. I amend my comment to not include center overflows......in a center overflow you are going to need something other than a durso for the drains, because dursos need to be relatively large to function well, and a single 1.5" will not do 1200 gph reliably, or even 600 perhaps. since full siphons are not safe to run stand alone, you are going to need more than one standpipe and the return system in the overflow. But you can use smaller pipe diameter pipe. FWIW :)

Jim

[d2mini]

<a href=showthread.php?s=&postid=15577297#post15577297 target=_blank>Originally posted</a> by das75

For interest, this link (http://www.oceansmotions.com/forum/viewtopic.php?t=1129) shows a dual ctr column overflows with notches.
Ah, yes I remember seeing that build recently. Mine will be similar but just one overflow. I didn't notice the caps on the overflow before. That would definitely help with jumping fish.


<a href=showthread.php?s=&postid=15577390#post15577390 target=_blank>Originally posted</a> by uncleof6
For a center overflow as much linear distance as practicality allows, and as much space for plumbing as you can. I amend my comment to not include center overflows......in a center overflow you are going to need something other than a durso for the drains, because dursos need to be relatively large to function well, and a single 1.5" will not do 1200 gph reliably, or even 600 perhaps. since full siphons are not safe to run stand alone, you are going to need more than one standpipe and the return system in the overflow. But you can use smaller pipe diameter pipe. FWIW :)

Jim
I was going to have a second 1.5" for an emergency drain if the first clogged up. But what would you suggest I do to get more flow? What would YOU do if you were going to build a center column overflow?

Thanks!

[das75]

Could do a classic Herbie with a 2" primary, 1" secondary or emergency drain, another 1" for the pump return.

[uncleof6]

A 1.5" full siphon? with emergency? that'll work. You could downsize to 1.25" also. The third pipe in bean's design makes it self adjusting, and I don't leave home without it, but in some cases, there just is not room for it. As far as the "length" of overflow, I would think with two 1.5" standpipes in there (with elbones) you would have enough linear distance without teeth. With that in there you are looking at about 8" square minimum inside. (which in this tank will give you more "weir" than a coast to coast would.)

The truth? Honestly? For real? I would do a zero edge instead. Aside from that, I would be shoving bean's design in there somehow, and I would be looking to make the water depth in the "box" shallower. But then that just might be me.

Jim

[d2mini]

<a href=showthread.php?s=&postid=15577661#post15577661 target=_blank>Originally posted</a> by uncleof6
A 1.5" full siphon? with emergency? that'll work. You could downsize to 1.25" also. The third pipe in bean's design makes it self adjusting, and I don't leave home without it, but in some cases, there just is not room for it. As far as the "length" of overflow, I would think with two 1.5" standpipes in there (with elbones) you would have enough linear distance without teeth. With that in there you are looking at about 8" square minimum inside. (which in this tank will give you more "weir" than a coast to coast would.)

The truth? Honestly? For real? I would do a zero edge instead. Aside from that, I would be shoving bean's design in there somehow, and I would be looking to make the water depth in the "box" shallower. But then that just might be me.

Jim

Thanks, Jim.
1.5" durso drain was the plan so far with a second 1.5" emergency durso drain.
Then I was going to do a CL with an OM SuperSquirt.

Here's my basic plan (minus the emergency drain in the side view).

And as far as teeth/no teeth... i guess i'm wondering if having teeth really prevent fish from getting sucked over the top of the overflow???

http://d2creative.smugmug.com/photos/626634012_e2yUs-O.jpg

[d2mini]

Ok, nowwww I'm starting to understand what you meant about full siphon. Like a Herbie overflow setup. I searched and found some good info on it and it sounds good. My only question is if the main drain is 1.5", what size should the secondary (emergency) drain be? The same?

[uncleof6]

Same size, normally dry...... but with a full siphon setup, it will not need to be that big. 1.5" will do upwards of 2500 gph. You can do 1.25" on a 1" bulkhead in the ball park of 1500 gph... give or take....a number of variables affect it, but I think you get the idea.

J

[d2mini]

Thanks! Very helpful.

[das75]

<a href=showthread.php?s=&postid=15582347#post15582347 target=_blank>Originally posted</a> by uncleof6
Same size, normally dry...... but with a full siphon setup, it will not need to be that big. 1.5" will do upwards of 2500 gph. You can do 1.25" on a 1" bulkhead in the ball park of 1500 gph... give or take....a number of variables affect it, but I think you get the idea.

J

sort of wondering how with just a siphon (not a pump) the flow could increase so much?

[uncleof6]

You cannot get 2500 gph through a drain, unless you pump 2500 gph to the tank-- obviously. Talking the capacity of the drain-- or how much you can shove in it before it starts arguing with you..... a durso will argue with you in the 300 - 500 gph range.......bubbles, noise, instability

J

[d2mini]

<a href=showthread.php?s=&postid=15582347#post15582347 target=_blank>Originally posted</a> by uncleof6
Same size, normally dry...... but with a full siphon setup, it will not need to be that big. 1.5" will do upwards of 2500 gph. You can do 1.25" on a 1" bulkhead in the ball park of 1500 gph... give or take....a number of variables affect it, but I think you get the idea.

J

Why 1.25" pipe on a 1" bulkhead? Why wouldn't they both be the same size?

[uncleof6]

You will be able to get more through the bulkhead with the larger pipe. Physics. 1" all the way will get some decent flow also, but I like some overhead, rather than at or close to the limit.

Jim

[Acrylics]

I'd use the smallest box that will accommodate the bulkheads you are trying to place in it. It will probably be 8 x 8" to 10 x 10" - somewhere in there. In either case, more than enough to handle the flow.

On teeth, a 1/4" tooth x 1" long will yield a nominal flow rate of 40gph so a 10 x 10" with 1" teeth will yield ~2700 at full capacity. 4 panels 10" long minus thickness of material leaves ~9" divided by 2=17-18 slots per panel times 4 = 68-72 in total. I'm conservative so I go with the lower number
But, you want to remember to oversize this a little to allow for clogging and allow for an air gap above the water line so I'd recommend 1.25"-1.5" on the height of each slot. You can always dam this up if it's too tall

HTH,
James

[2_zoa]

<a href=showthread.php?s=&postid=15596689#post15596689 target=_blank>Originally posted</a> by Acrylics
I'd use the smallest box that will accommodate the bulkheads you are trying to place in it. It will probably be 8 x 8" to 10 x 10" - somewhere in there. In either case, more than enough to handle the flow.

On teeth, a 1/4" tooth x 1" long will yield a nominal flow rate of 40gph so a 10 x 10" with 1" teeth will yield ~2700 at full capacity. 4 panels 10" long minus thickness of material leaves ~9" divided by 2=17-18 slots per panel times 4 = 68-72 in total. I'm conservative so I go with the lower number
But, you want to remember to oversize this a little to allow for clogging and allow for an air gap above the water line so I'd recommend 1.25"-1.5" on the height of each slot. You can always dam this up if it's too tall

HTH,
James

Can you be so kind as to break this down into a long hand version? The way I read it, and me doing the math I don't get it.

The 10x10 is length and width right? Or is that 10 panels 10" wide? A 10" wide piece gives you 20 slots or areas for flow. If a 1/4x1 will flow 40GPH then that panel is only good 800 GPH. If the OF is a square in the middle of the tank then it will be good for 3200GPH? If you remove the corners that will equal 1" worth of flow so it is now good for 3040GPH.

9 divided by 2 does not equal 17-18. It is 4.5. If you then times that by the 4 panels you will get the 18. Which I am guessing is now your flow area, giving you 18" to flow water through. If you mutiply that by 4 that will give the 72. However this should be 72 slots not inches of flow.

Am I way off on this?
Does anyone else read it this way?

Oh yea, this all comes out to either 36" of OF length or 40" of OF length depending on which number you go with the 9" or the 10".

[Acrylics]

<a href=showthread.php?s=&postid=15599178#post15599178 target=_blank>Originally posted</a> by 2_zoa
Can you be so kind as to break this down into a long hand version? The way I read it, and me doing the math I don't get it. Sure thing :)
A 10 x 10 overflow is 4 panels, each face being 10" wide. A 10 x 10" square "island" overflow.

Out of each panel, you will lose the material thickness for slots, can't put a slot there so subtract out the material thickness plus a little so only ~9" available for slots.

Depending on how you start your slots, you will get 17 slots, maybe 18 out of that 9" lay it out and you'll see.

So each panel has ~17 slots x 40 gph per slot = 680 gph per panel
4 panels so ~2720gph

The above is based on 1" slots and my experience. Again, I'm conservative, I'd add for the chance of clogging and the air gap above the water line.

IMO completely forget the RC calculator when it comes to slotted overflows, it does not apply.

[das75]

on RDO (here) (http://www.reefs.org/library/downloads/) there's a great down-loadable Excel spreadsheet for playing with slotted overflows. The variables are width and number of openings and it calculates the height up the slot and flow (gph).

Can also be used for a straight weir to find the height above the lip (number of openings = 1)

[2_zoa]

<a href=showthread.php?s=&postid=15600897#post15600897 target=_blank>Originally posted</a> by Acrylics
Sure thing :)
A 10 x 10 overflow is 4 panels, each face being 10" wide. A 10 x 10" square "island" overflow.

Out of each panel, you will lose the material thickness for slots, can't put a slot there so subtract out the material thickness plus a little so only ~9" available for slots.

Depending on how you start your slots, you will get 17 slots, maybe 18 out of that 9" lay it out and you'll see.

So each panel has ~17 slots x 40 gph per slot = 680 gph per panel
4 panels so ~2720gph

The above is based on 1" slots and my experience. Again, I'm conservative, I'd add for the chance of clogging and the air gap above the water line.

IMO completely forget the RC calculator when it comes to slotted overflows, it does not apply.

I didn't word it as cleanly as you just did. I got it now. Thank you.

[2_zoa]

<a href=showthread.php?s=&postid=15601003#post15601003 target=_blank>Originally posted</a> by das75
on RDO (here) (http://www.reefs.org/library/downloads/) there's a great down-loadable Excel spreadsheet for playing with slotted overflows. The variables are width and number of openings and it calculates the height up the slot and flow (gph).

Can also be used for a straight weir to find the height above the lip (number of openings = 1)

Nice link, I saved the link and downloaded the spreadsheet.

Thank you for sharing.:D