Spot any logical fallacies? Overflow plan.

[Gorgok]

I am finally getting rid of my 30" high ~70 gallon corner tank, and going with a blank 75 gallon glass tank (which looks massive next to the corner...) and plan to 'do it right' since i now know better. It will have a BA overflow setup, 1.5" bulkheads and pipes on all, and an over the top return. I don't want an overflow box inside the tank big enough to house the bulkhead install and elbows... so as i have often recommended i plan to put a narrow sloped glass overflow in it. I like to plan properly, so i have done it on the computer to some extent, but now i need feedback to see if i am missing something or have some other mistakes in the plan.

I don't know how hard it is to get those little knife edges for the angled glass weir ends, but i don't imagine its impossible, plus it doesn't have to actually go to a razor point as the silicone will be there too. I think i drew that as a 10 degree slope, thinking any narrower and it gets too tight near the bottom of the holes. I also have never cut glass before trying it once yesterday, but i learn quick and it came out just fine i think. Also i could probably put the side pieces outside the front piece, which would let me not have such a sharp point on them, but that would probably be less pretty. (Pretty > less pretty)

I planned to make the plumbing 'removable' to a great extent, but i don't want screw fittings, so the only good solution i came up with was installing the bulkheads backwards. This may not make sense, but if i glue everything from the bulkhead down as one piece i can remove it by undoing the bulkhead nut. Then if i machine an o-ring groove onto the siphon and open channel pipes i can pull those assemblies out of the bulkheads yet seal when in place. (I didn't draw the air line port to the open channel elbow assembly, but assume one is there.) Not that i have found a need for o-rings on pushed together plumbing generally, when enough force is used... but its not hard to do so might as well. Any obvious issues there?

My siphon and open elbows end at the same height, but i can always add pipe to either to to make one lower, as they are a little high due to the bulkhead tail being so long. I will have to machine off some of the tail and shorten up my elbows to get them to sit a little lower (mainly for pretty, full size it would still work I'm sure but peek over the top a bit). I could also use street elbows to get them lower, and may do so, but they look 'odd' when next to a real elbow, so it would be less pretty. The box design sort of runs out of room for more elbows on the emergency drain, but that shouldn't be an issue i imagine. It is supposed to only get wet when there is something wrong...

I also didn't use any tees, as in the original plan, but i honestly don't plan on cleaning my pipes, just like 90% of everyone else, so i don't really see a point in specifically accommodating it. I am much more likely to have to remove my plumbing to move/change something than i am to choose to clean it, at least that's how i see it. Of course, if my box internals are easily removable then cleaning is possible through the bulkhead directly.

I don't have any bracing on the underside of the box, but i probably will add some just because i will have the glass to do so, and no good reason not to... Though it is probably prettier if i don't put any, or instead put some cross bracing inside the box instead. (Pretty is pretty important...)

Gate valve location is one thing i remember reading about some time ago, but searching didn't find the same thing i remember. I am wondering if it matters how high/low it is put. I don't have a problem putting it as high as possible or as low as possible, but i thought i had read something about one or the other making starting a siphon harder. Which way is best? Or just put it where its most convenient? (Most convenient is probably immediately after the 45 bend at the edge of the stand.)

Not sure i asked anything except about the gate valve, but comments on anything else would help too.

 

[uncleof6]

Everything is too small. The overflow box is too short. You want ~1" (+ is ok) from the top of the weir (overflow) to around the top of the down turned elbows, where the water line will be; the dry emergency is way too short, it needs to be well above the tops of the down turned elbows, close to the top of the overflow. The holes should be low (or high) enough that the water line in the pass through holes is at the middle of the holes, this minimizes friction losses, and noise, and maintains surface skimming from the internal to external box (very important.) There really isn't anything to gain by having a sloping weir, (and you may have water piling up because of it, (waterfall hitting the back glass,) so you want to square it off @ ~ 2" - 3"; the weir should be the entire length of the tank to maximize surface skimming/surface renewal performance.

Most people don't know what evil lurks in their drain lines, unless they actually run the tank a while, and bother to have a look at all the grunge that grows, and clings to the walls of the pipes, a good place for sponge growth. Folks don't clean their drain lines, because it is work, not because it does not need to be done. If it did not need to be done, a provision to do so would not be part of the design. Bean is a pretty sharp fella...

Also, 1.5" bulkheads are too big for this tank, as you won't be anywhere near wanting to flow above 1500 gph (which is the only reason to go up to 1.5" bulkheads.) 1.5" pipe? Well you can get 1200 gph out of 1" pipe, but 1.5" pipe is ok. Your pass through holes should be sized for 1.5" bulkheads, and the more of them the better (keeping safe spacing in mind.)

In Bean's thread, you can find the designs that I did for this idea, which I believe, I was the first to design. Bean and I discussed the design. I know you want to minimize the footprint, but you will get much better performance if you do it right, rather than trying to minimize things.

Valve placement, except in a long basement drop, really doesn't matter. For long drops, put it at the sump.

 

[Gorgok]

I had overlooked the amount of space the water will need in the internal box to travel to the external box indeed... Is there some math i could do to see how wide it should be at half hole height with different flow rates? Moving or adding holes isn't an issue either, and a longer external box to accommodate. I just can't see myself making a 3" wide internal box then an external box, as that is wide enough to make it an internal box already (even with 1.5" bulkheads). I will have to try this out in the plans to see if there is any point in going on with the external box as a result. Having a clearer picture on the sizing requirements would help though.

When you say it is important to maintain surface skimming in the external box i don't quite follow. If the sheet of water from the top is dropped into the overflow, isn't it guaranteed to go down the drain? Unless you mean it getting trapped in turbulence like air in the back of a truck, off to the side of the holes spinning around until the pump stops and the whole box dries up (to a point obviously). If this is the case then another strike for internal/external boxes, as i'm sure the water towards the far ends will be turbulent and get passed by the water directly opposite the holes. Only a true internal slot/external box would work as good as internal box then. That is not really something i want to try on a glass tank though.

I do understand wider is better, but i don't want to mess with the existing silicone in the corners with the new silicone for the overflow so i thought leaving a couple of inches off the ends would be simpler. Especially when the return will be in one of the gaps. I can probably stretch it a little more, depending on return pipe size. Also technically if the box is 3" wide, and 3" off each end its the same length of weir as a coast to coast is.

The pipe choice was mostly due to always reading about using 1.5" for the emergency and open channel, while 1" would suffice for the siphon in most systems. But not wanting to have different sizes for sake of simplicity, and running them all at 1" being too small (and apparently 1.25" being uncommon in bulkheads), so the compromise of 1.5" made sense to me. I understood from the BA plan that the use of 1" bulkheads was simply a matter of convenience since those were what he had at the time, but the pipe size was more important. I just got bulkheads to match my pipe choice, not for flow capability. Not a big deal to correct if it is indeed an issue.

This is why i'm here though, i do intend to correct the problems in the plans before anything takes to the drill.

 

[palmerit]

When I setup my internal c2c overflow, I wanted maximal surface skimming. I used a piece of glass, similar to your design. I lost a couple fish into the overflow. Please, whatever you do.. Design some way to prevent livestock for going over with the sheet of water. I had to drain half my tank for 2 days to rectify the issue. And the end result was ugly as hell. I've glued some gsp frags to the 'workaround fish death prevention' and am hoping a nice thick carpet of gsp covers the monstrosity in time.

Do yourself a favor, and plan for that now, so it can be made functional AND somewhat attractive.

 

[Gorgok]

You want ~1" (+ is ok) from the top of the weir (overflow) to around the top of the down turned elbows, where the water line will be; the dry emergency is way too short, it needs to be well above the tops of the down turned elbows, close to the top of the overflow. The holes should be low (or high) enough that the water line in the pass through holes is at the middle of the holes

I thought the water line ends up being right around where water can finally enter the open channel when adjusted right, which on 1.5" pipe is ~2" lower than the top of the elbows. Is the placement of the pass through holes based on the water level being there (~1" below) the weir, or at the point where water can enter the open channel (~3" below the weir)?

Dropping the tops to at least 1" under the overflow edge is not an issue, especially if i just use street elbows, as that will reduce the assembly height over an inch. Making the box taller (down) is not an issue either, it just doesn't seem necessary even with these numbers using smarter plumbing bits (like the street elbows). Making it taller up is much harder i would imagine, as it gets butted up against the outside trim as is in the plans (not showing on that version). I imagine i could notch the glass to go around the trim and fill the gap between the trim and the tank inside the external box with silicone if necessary.

Is the ~1" drop to the top of the elbows is a physics requirement, to make sure there is enough drop to start the siphon? Would a larger opening like on 1.5" bulkheads need more drop than the 1" ones in the plan?

I think a 2" weir is workable while still appearing small enough, squared off and deep enough to just cover the holes, wherever they end up...

Still working on an updated plan with these corrections.

 

[uncleof6]

That is where water level winds up, which is usually right within the top 1/4" - 3/8" of the tops of the elbows... the 'weir' inside the elbows + head height (where the water heads down)

The 1" drop is to insure sufficienct surface skimming of the tank... there is more involved than meets the eyes at first, follow the design criteria, and you won't have issues.

The box does not need to be taller, rather the external box needs to be 'deeper' top to bottom...the internal weir should be 1" down from the top of the glass, which is usually at the bottom of the trim on the outside... also hides the water line (head height behind the weir.

Remember, function first. Appearance comes last, as the function is far more important...

Becasue I doubt you have hunted it down in Bean's thread, here is the pattern for a 4' tank: (add 1/2" above the top for a rimmed tank. The top of the glass is the reference in this pattern, and this pattern maintains safe distances from hole to hole, and hole to glass edges. With an internal/external, you end up with a longer drop into the overflow.)

 

[Gorgok]

Top of elbow is red line? Water line is blue line? Or you mean top of elbow is blue line?

Putting the emergency well past the red line top of elbows would put it out of the external box pretty quick (even with the elbows lowered), which is why i thought it might need to be taller.

 

[uncleof6]

Well, I told you, you are trying to make everything too small. Look at the pattern above...top of the elbows defined is the upper half of the horizontal part of the elbow...the whole outside box is just plain too small...appearantly you are stuck on that, but you are going to have to become 'unstuck.'

Here is an example, the first internal/external full design; water line will be where it is, sometimes a bit higher, hence ~ the top of the elbows...On the actual build, I did shorten the box, to take up the slack in the pipes, and used screw on caps, which lowered the caps below the top of the tank..

 

[Gorgok]

That picture is just a copy of the original with lines added to try and clarify what you mean by the top and what i am understanding as the top. It serves no other purpose for the plan anymore.

Missed the answer in the previous post though.

 

[uncleof6]

That picture is just a copy of the original with lines added to try and clarify what you mean by the top and what i am understanding as the top. It serves no other purpose for the plan anymore.

Missed the answer in the previous post though.

Ok. I am just trying to be thorough is all...

 

[Gorgok]

Internal is now 2" wide inside. More holes and spread farther apart, without going to the extreme of having the external box being as wide as the tank... I do plan to stick this into the corner where the old tank is, so my external size is limited by the walls, can't make it wider without having the tank stick out more so than it will with the back corners touching.

External also deeper, as recommended, but not the 8" (+trim) in the plan above, only to 7" as it already looks strange to me to have the elbows that high up off the bottom. The pass through holes are at ~3" which puts their middle directly where the elbows weir is (accounting for the wall thickness of the pipe/elbow), deeper than in the plan above (probably due to pipe size difference?). The elbows themselves are 1" below the weir to the red line top, as is the emergency.

 

[Eud]

Will you be able to see the silicone seam holding on the external box from the front now that it is deeper than the inside box?

 

[RocketEngineer]

Here is mine when first set up:


Last month:


Depending on how you do the rock work and the coralline algae, they tend to blend into the background.

Personally, I found the BeanAnimal system worked best when the side opening in the tee for the Durso and emergency was one pipe diameter above the siphon. The first picture above shows this best. The way you have it currently, the siphon won't start because the Durso and siphon are at the same height.

 

[Rognin]

Here is mine when first set up:
*SNIP*

Last month:
*Snip*
Depending on how you do the rock work and the coralline algae, they tend to blend into the background.

Personally, I found the BeanAnimal system worked best when the side opening in the tee for the Durso and emergency was one pipe diameter above the siphon. The first picture above shows this best. The way you have it currently, the siphon won't start because the Durso and siphon are at the same height.

This isn't true. Nice tank though!

 

[uncleof6]

Here is mine when first set up:


Last month:


Depending on how you do the rock work and the coralline algae, they tend to blend into the background.

Personally, I found the BeanAnimal system worked best when the side opening in the tee for the Durso and emergency was one pipe diameter above the siphon. The first picture above shows this best. The way you have it currently, the siphon won't start because the Durso and siphon are at the same height.

I have a couple hundred of these things running, (3hp and all,) have never seen a starting issue (unless I intentionally created one) with the elbows all at the same level. I classify the problem this solves as the bulkheads being too large for the flow rate. That may or may not be the case/issue with your system.

There have been problems with lower flow rates ( < 1500 gph) using 1.5" bulkheads. The solution is in the planning phase: e.g. if you are not going above 1500gph (depending on length of drop) no reason to use 1.5" bulkheads. The bottom line being: 'as designed works' with no modifications.