Bean Animal Overflow: Airline Question.

[fishbox]

From what I'm reading on Beans original thread and web site it sounds like the inlet of the airline should be a tad above the inlet of the emergency drain. However, I wanna make sure that I'm reading it correct because I've seen some people with it just below the inlet of the emergency drain.

 

[madweazl]

I would think it should be below the emergency standpipe so it can go full siphon prior to the emergency pipe going full siphon.

 

[fishbox]

This is directly from Beans web site and is where I'm confused

2) The Open Channel (right) standpipe is equipped with an airline that is attached in the overflow box. If the water level rises to the critical point of overflow and the Emergency (left) standpipe can not handle the flow (say due to blockage from algea or something) then the water will cover the inlet of the airline. The flooded air intake will in effect convert the Open Channel (right) standpipe into a full siphon standpipe, allowing it to handle much more flow. This will flush the overflow box and prevent flooding.

 

[saltyhog]

I prefer it to be below the emergency drain. My reasoning is it is a wet drain and therefor much more susceptible to obstruction due to that. Which ever one is higher is the last line of defense. I would prefer the last line of defense to be the one least likely to fail (become obstructed). I really think it's ok either way. It would take pretty impressive bad luck for all three drains to fail!

 

[DaveMorris]

Airline should be just above the emergency drain.

 

[fishbox]

I prefer it to be below the emergency drain. My reasoning is it is a wet drain and therefor much more susceptible to obstruction due to that. Which ever one is higher is the last line of defense. I would prefer the last line of defense to be the one least likely to fail (become obstructed). I really think it's ok either way. It would take pretty impressive bad luck for all three drains to fail!

That's exactly what I was thinking. There's water flowing in the OC and therefore a higher risk of it getting clogged. Why would that be last defense?

 

[ronl]

Bean's reasoning for having the dry emergency kick in before tripping the wet drain to siphon is to aid in start up to get the main siphon line siphoning. During start up, the water level in the overflow will usually rise above the level of the dry emergency, which then creates a stable water level to allow the main siphon line to purge air and go to siphon, which then lowers the water level in the overflow. When the wet line goes to siphon first, it will usually cause the water level to fluctuate as it goes back and forth between siphon and non-siphon. This varying level in the overflow makes it harder for the main siphon line to purge the air and go to full siphon.

 

[saltyhog]

thanks for the explanation ronl! For what ever reason my airline is below the level of the emergency drain and I have no issues on restarts with getting the line to purge air. I even have a single 90 degree elbow in my full siphon.

 

[ronl]

Yeah, every set up is a little different, so some people don't have issues even if not set up as Bean designed it. Question...does your main siphon line go to full siphon before the airline gets submerged? If so, that could be the reason why you have no issues. Mine goes to full siphon when the water level gets to about 1/4" below the top of my emergency drain pipe, so the emergency never takes on water and the airline never gets submerged. But some set ups will need to use the emergency pipe or have the air line submerged before the main siphon kicks in. In those instances, Bean says it's better for the dry emergency to take on water first to maintain a stable water level in the overflow so it is easier for the main siphon to kick in.

 

[saltyhog]

Water does get to the air line intake but just as the full siphon kicks in. My open stand pipe is a little higher than the full siphon and a little lower than the emergency. Does that have something to do with it?

 

[fishbox]

Yes, thanks for the explanation!

 

[ronl]

Water does get to the air line intake but just as the full siphon kicks in. My open stand pipe is a little higher than the full siphon and a little lower than the emergency. Does that have something to do with it?

Sounds like your main siphon is kicking in just before the open line goes to siphon. If the open line went to siphon first, it would lower the water level in the overflow, which would break the siphon on the open line. Then the water level would rise again until the airline is submerged and it goes to siphon again. The main siphon line needs a certain amount of head pressure to purge the air and go to full siphon. The amount of head pressure needed depends on the length of drop to the sump, how deep the pipe is submerged in the sump, number of elbows, horizontal runs, etc. Your system is creating enough head pressure right as the water is reaching the airline. If it needed any more head pressure, you might experience an issue with the water level dropping as a result of the open line taking more water when the air line is submerged. When the water level drops, the head pressure drops and it could take longer for the main siphon to kick in.

Alternatively, by having the emergency pipe lower than the airline, if the emergency line does need to take on water before the main siphon kicks in, the height of the emergency pipe will keep the water level in the overflow more steady until the main siphon kicks in.

 

[fishbox]

Alternatively, by having the emergency pipe lower than the airline, if the emergency line does need to take on water before the main siphon kicks in, the height of the emergency pipe will keep the water level in the overflow more steady until the main siphon kicks in.

Without this is it possible for the Overflow box to then overflow causing a flood?

 

[ronl]

Without this is it possible for the Overflow box to then overflow causing a flood?

As long as your drains sit low enough in the overflow box, you should have a problem with flooding. After all, you have 3 drains to take the flow. The problem would be that your main siphon line could have a problem going to full siphon. I'm not saying it will happen, but in some set ups it could happen.

Picture a scenario where the air line gets submerged before the main siphon kicks in. Once the air line is submerged, that drain will take on more water flow, thereby lowering the water level in the overflow box. Once the water level lowers, the air line will be exposed again and the water level will rise again. Then the air line will get submerged again and the water level will drop again. This fluctuating water level can make it difficult for the main siphon line to go to full siphon. If that happens, then you have a loud overflow that is alternating between sucking air and sucking water until the full siphon line finally kicks in.

The more vertical distance you have between the siphon line and the end of the air line, the less likely this is to be a problem. And there are many set ups running fine this way. It is more likely to be a problem on shallower overflow boxes where the vertical distance between the two is smaller. Having the dry emergency pipe lower than the air line simply allows for a more stable water level so the main siphon line has a better chance to go to full siphon.

 

[fishbox]

Got ya. Once again a great explanation.

Thanks