Bubbles breaking the syphon in my overflows. ?

[feralhuman]

I just started this system. This is probably a common problem with a well know solution. But I could not find it with a search. It seems my (2) one and one quarter inch lines are pulling air with the water as it flows into the tubes. The bubbles quickly pile up in the syphon system until it stops working as it is full of air instead of water. The pipes are just open at the top at this point. it seems like some kind of screen or something to break up the water as it falls into the pipe would help. Or something like that? Or maybe pipes are just far too small for the volume. It's a 150 gal tank and I have the jebao 12,000 on it's lowest setting.
Suggestions?
Thanks.

 

[Drstrangelove]

Post pics. Easier to see what you mean. I'll try to give and an answer, but it's a conjecture.

Are you talking about 2 over flow tubes (standpipes)? I'm guessing with no pic, that you mean this.
http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

It sounds like both tubes are taking water (thus level) and neither is under full siphon (thus taking air.)

My understanding is that when you have 2 overflows, 1 is supposed to be set lower than the other, have a valve, and be sized so it can take at least all of the overflow of the tank, i.e., under full siphon. In full siphon the entire tube is full of water and contains no air. In this model, you can adjust the valve to balance the overflow with the intent that the lower pipe runs full all the time and thus silently while the other higher standpipe is empty and takes very little water or simply takes small amounts.

The second pipe will take any surplus over flow and act as an emergency pipe in case the lower standpipe is clogged or stopped. The valve in the lower pipe will let you balance the flow to reduce water discharge noise.

If you have 2 tubes acting as described (both making noise and both open), then it sounds like they have the same level (not how the linked design works) and that there is no valve. It's also possible that both tubes are too large for the intended overflow, but if they are the same level, you may get the gurgling even if they are correctly sized for the pump.

I haven't built one of these, but I suggest you post a picture as it will certainly help others who have built these.

 

[feralhuman]

^ It's exactly as you describe. I have 2 standpipes at equal levels, both of them are making slurping noises. I wasan't concerned about the noise, but apparently the noise is an indicator of a vortex, as per the link you supplied. My original goal was a highly adjustable flow rate, I guess I hadn't read enough to understand the problem of vortex.
I'll see if I can get some pics up.
Thanks.

 

[jaws7777]

Could lowering the stand pipes stop the vortex from forming ?

 

[feralhuman]

^ If both of them are lowered that will lower the water level in the fish tank. But lowering one might be a good option. Especially if I install a valve to lower the flow rate. I'm thinking I'll first work it the other way by raising the height of the pipe where the water pours into the filter, thereby raising the water level in the standpipes. That will probably slow down the flow, but maybe the air won't get sucked all the way down into the standpipes. Valves for flow control are almost certainly needed.

 

[DN328]

Short of pictures, but suspect you will need to lower the pipe designated as the primary full siphon drain. This could be fixed by raising the second, increasing water level, but it's hard to say without knowing you setup and the amount of water.

 

[feralhuman]

I get it now. And I partly have it fixed, with the info I got here. The bottom line is that for this flow rate the primary overflow has to be submerged deep enough that it can't form a vortex and suck air down the vortex and into the pipe., therefore breaking the syphon. And the water going into the emergency overflow,which is at the top of the water, has to have a volume small enough that it does not suck air down into the pipe, therefore breaking the syphon. I used a pair of one and one quarter inch lines. This will work ok as long as I keep my pump on the lowest setting, not really awesome, but ok.
If the flow is fast enough in the pipe it will get air, or half of the water in the tank will go into the sump if something goes wrong. I should have went with much bigger pipe. The pipes can handle volume, but that goes out the window when air is added to the equation.
Much of this is not an issue if nothing ever goes wrong, I always assume something will go wrong.

 

[DN328]

feral, you got the concept down, but something doesn't seem right. With 1.25" drains, you should be able to run higher than the lowest setting on the Jebao 12,000 (I have a Waveline 12000 which should be similar).

Do you have an internal or external overflow? Or do you just have Standpipes in the tank? Also, do you have any valve on the primary drain to control flow? Based on what I've seen, even 1.25", smaller or larger drains will require a valve to balance drain rate with the return rate of the pump. You never specified how you have it set-up or a picture. Again, with 1.25" pipes you should be able to run much higher than the lowest setting, IMO.

 

[hart24601]

I agree something is off. I have a sicce 5.0 (1300 gph) and 1" drains. The primary drain I have very restricted with a gate valve. That pipe should be able to flow a lot.

 

[Drstrangelove]

I honestly think it would easier if you post pics. I've seen threads where a single pic was enough for someone to state exactly what needed to be done. Again below is my understanding of the process:

A Jebao 12,000 is rated at 1,878 gph @ 6 feet and 2,540 @ 3 feet heat. A 1.25" pipe at full siphon can pull nearly 3,000 gph with only a 30 inch drop. (Deeper drops of 48" will pull over 4,000 gph.)

Thus, a 1.25" overflow should not have a problem handling that pump at full siphon. If anything, you should be forced to valve back the 1.25" to get it to pull less, not the opposite (tuning back the pump.)

I do agree that had you run the pump at full with (2) 1.25" standpipes each at the same level, that both would have drawn in air. One might have reached full siphon for a moment which would have immediately lowered the water level and broken siphon. But if the inlet for the emergency pipe is now higher, I can't picture how it's not working with the pump at full output.

My question is have you now tried running the pump at full with one of the 1.25" pipes now lowered and the emergency pipe higher? If so, what was the result.