DIY overflow Pic, and questions

[nanoluvr]

I saw this thread, and am going to build it in the next week for my buddy's 58 gal. Looks like it works good for the author of the thread I got it from, and way cheaper than the $100 + overflows from retailers!

Thw water gos in through the little slots on the top...it's sitting sideways in the pic, lol, and it has a little check valve in the top.
Supposed to not lose syphon in power outage.

Does anyone have any recomendations on a float switch that will can be installed in the sum,p to prevent overflow? And also, any suggestions on wiring it up?

 

[goisles1]

no info on the check valve... BUT....

I made that exact Overflow and it's currently on my tank. I had a bunch of issues with it losing siphon. It actually overflowed my DT 2 times. Thankfully, I was in the room and was able to kill the pumps before too much water got on the floor.

Not sure why, but AIR gets into my piping and breaks the siphon. I ended up buy an AquaLifter for $10 and connecting it to the Check Valve. Now it works fine. Anytime Air gets into the tubing, the lifter sucks it right back out. And I'm protected if power loss as the Aqualifter starts the siphon again when power is restored.

Last thing.. Instead of doing the slots for the water to enter, I installed a threaded elbow instead and bought a 3/4in threaded strainer from MarineDepot for $3.

 

[jsoong]

What I found with DIY overflows is that there will always be entrained air when you skim the water off near the top. The air will clear the siphon if the water flows fast enough. <This is true of commercial overflows as well. So in the wier type overflow, where the velocity is low, you need a venturi pump to remove air bubbles.>

In my overflow, at 750gph nominal, I got air trapping in the siphons when I have 2 1" siphons. <The water level difference between the inner box & outer box was 1/4 to 1/2" - very little driving pressure so fairly low velocity flow.> When I removed one of the siphons, the driving pressure increased to 1" or so. The flow through the single siphon was much increased, and that flushed out any air bubbles that got trapped & I have had no siphon breaks since. .... *touch wood*

 

[ccCapt]

I'm all for DIY, but not in the case of a overflow. IMO, you are much better off buying 1. You can get an 800 gph overflow box, which is plenty for a 58g tank, for $57.

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+3579+18358&pcatid=18358

 

[goisles1]

I'm all for DIY, but not in the case of a overflow. IMO, you are much better off buying 1. You can get an 800 gph overflow box, which is plenty for a 58g tank, for $57.

Reef Aquarium Filtration: Eshopps Overflow Boxes

With all the issues I've had, I'll have to agree with you on this.

I have a question about those ESHOPS overflows... I really like the DUAL model and may buy it. I notice they do NOT have to be hooked up to a Aqualifter or any Venturi type pump. Will I be able to sleep at night as is or would I look to incorporate a pump into the siphon just to be safe?

 

[nanoluvr]

I'm all for DIY, but not in the case of a overflow. IMO, you are much better off buying 1. You can get an 800 gph overflow box, which is plenty for a 58g tank, for $57.

Reef Aquarium Filtration: Eshopps Overflow Boxes

Interesting... any reason why DIY on the overflow is no good, IYO?

 

[nanoluvr]

Capt, ...I was also wondering...with the Eshopps OF box, is the siphon broken when power goes out (to prevent flooding), and then regained again when power returns?

 

[ccCapt]

Interesting... any reason why DIY on the overflow is no good, IYO?

Because I have yet to see 1 that is reliable and that I would trust using.

is the siphon broken when power goes out (to prevent flooding), and then regained again when power returns?

The siphon DOES NOT get broken when power goes out. I used a HOB overflow for over 15 years and it never once failed. I have total faith in them. The U-tube style does not require an aqaulifter pump like the CPR style overflows.

 

[nanoluvr]

The siphon DOES NOT get broken when power goes out.

Pardon my ignorance, lol. All 3 of my reef tanks are nano (20 and smaller), sans sump, so overflows haven't been necessary. If the siphon is not broken during an outage, does water keep going into the sump? If so, how do you keep it from flooding if the return pump doesn't have power? Or do you mean the syphon isn't broken as far as when the power is off, flow stops, and when it comes back on, flow returns?

 

[goisles1]

The siphon DOES NOT get broken when power goes out.

Pardon my ignorance, lol. All 3 of my reef tanks are nano (20 and smaller), sans sump, so overflows haven't been necessary. If the siphon is not broken during an outage, does water keep going into the sump? If so, how do you keep it from flooding if the return pump doesn't have power? Or do you mean the syphon isn't broken as far as when the power is off, flow stops, and when it comes back on, flow returns?

Yep.. How it works is the Overflow actually has 2 boxes. One sits inside the tank and the other sits outside. The inside box will always be filling up with water as it is under the waterline. The U-Tube transfers the water from the inside to the outside boxes where the bulkhead is and it drains down to the sump. However, when the pumps are off, the tank will only drain until the water level is even/below the inside box.

Once it reaches that level, the water can't enter the inside Box anymore, and the flow stops. However, the U-Tube remains filled with water or "primed" and once the pumps start filling the DT again the water overflows into the inside box and the siphon starts up again.

 

[nanoluvr]

Ahhhhhhh...I see now. Very nice. That's what I'll do then. I appreciate your help. The sump will be 20 gallons and sit approximately 4 to 5 feet below the top of the tank. Any recommendations (with that 800 gph OF box) as far as return pump capacity. Do I understand correctly that with the pump below the tank, it will lose capacity? (i.e. 1000 gph is more like 600?)

 

[jsoong]

The pump manufacturers publish tables of flow rate at different head height <ie the distance from the pump to the top of your tank>. You look up the table (Google it, or it is usu. printed at the side of the box) for the pump you are interested in & size it that way.

For those who want to see a nice pic of how the HOB overflow works:
Melevsreef.com - What is a Sump?

 

[gzeiger]

Sorry to dredge up old topics, but this is actually the most recent on the topic.

I'm working with a HOB overflow (came with a used tank) that has a u-tube type siphon. I've been trying to figure out any kind of fail-safe to deal with a broken siphon. It sounds like you guys are saying that with sufficient flow velocity it just won't ever break. Does experience really back that up? A broken siphon would make a 50 gallon spill in less than ten minutes with my present design. Is there any engineering solution to that?

 

[ccCapt]

It sounds like you guys are saying that with sufficient flow velocity it just won't ever break. Does experience really back that up?

As I mentioned earlier in this thread, I used a u-tube style HOB overflow for over 15 years without having it fail once. Is that enough experience?

 

[CaptainAhab]

I keep my return raised on an eggcrate stand enough above the bottom to theoretically take care of it. If the overflow ever fails, the water level drops and the pump burns out. Never happened but that's my plan Stan.

 

[gzeiger]

As I mentioned earlier in this thread, I used a u-tube style HOB overflow for over 15 years without having it fail once. Is that enough experience?

Well, yes and no. It seems like it would be dependent on the design of the overflow box. The more turbulent the overflow, the more entrained air and the more likely the siphon will break. I've never used one before and I don't know how different they might be.

I may just run it for a few days, or do a proper cycle, with just a couple inches of water in the sump. The way my overflow is designed though the water level is going to be absurdly close to the top of the main tank.

 

[ccCapt]

It seems like it would be dependent on the design of the overflow box.

As far as I know, there is only 1 design for a u-tube overflow. A box inside the tank, a box outside the tank and a u-tube connecting the 2 boxes.

 

[gzeiger]

I was thinking more about the depth of those slits at the top and the width of the box, which can be varied. The narrower the box and the shallower the slits the more turbulent the overflow would be, right?

I'll just have to try it and convince myself I think

 

[CaptainAhab]

I think ur over thinking it. However I believe there are those that put small tubes run by small powerhead in their tube as insurance. Keeps the water flowing, I think is the thought process.

Vague recollection kinda somewhat

 

[jsoong]

Having built my own overflow, I can attest that design is important. The depth of the water in the boxes & how far down the siphon sits in the water are important parameters. Basically, if water has a long way to fall in the outer box, more air bubbles are created. If the siphon is down deep, less bubbles gets in. After tweaking, I have not have a siphon break for over 2 years now on my latest DIY effort ..... I am sure a commercial one would do better.

Personally, I am leery of using a PH to evacuate air from the siphon. When your power goes out, there is bound to be leaks in the pump, and if the pump don't start up when the power comes back on, you have trouble. <That's why I don't go for the wier type OF, which needs the PH.>

And I also raise my pump up in the sump to limit the amount of water it can pump in case of OF failure. Never need to use it, but a good insurance.