Silent and Failsafe Overflow System

[chatyak]

The potential issue with the BRS setup is that at startup, the water level needs to stay high enough for the siphon channel to purge all of the air so it can reach its steady state flow. When the air inlet on the open channel pipe gets occluded, the open channel converts to a full siphon, dramatically increasing the flow and draining the overflow box. If that conversion and drop I level is enough to prevent the siphon channel from completely purging itself the system will just continue to oscillate and never reach a steady state.

As they have it designed, it may well work fine, because he open channel is set higher than the siphon channel, so if the air inlet on the open channel gets occluded and converts it to a full siphon, it may switch back to a lower-flowing open channel before the level gets low enough to disturbs the siphon channel, allowing it to continue to purge air.

Makes sense. I guess it'd be a good test to know how high/difference that has to be between open pipe hole and main siphon.

 

[jason2459]

Tested a setup like BRS'?

If I read it right I think so. I setup the open chanel air inlet lower then the emergency. Then simulated a partial blockage of the siphon. Again I still haven't watched the video.

 

[chatyak]

Yeah I tested this. It oscillated continuously. Reverted back and all worked as normal.

You tested the BRS way? Video would be awesome if you have it.

 

[jason2459]

You tested the BRS way? Video would be awesome if you have it.

Sorry I don't but can try later. Though tonight I'm playing with a new skimmer.

Basically as the water rose the air inlet converted the open chanel to a full siphon basically at just the same time the emergency was just taking on water but then the full siphon on the open drained the water out of the back overflow because its not cut back and intune with the return pump like the normal siphon line is. Once purged of all the water the open channel lost siphon and became an open channel again. The water began to rise again and the cycle started all over again.

Reverting back to my airline slightly above the emergency allowed the partial failure of the siphon to fail into the emergency drain and continue on just fine with out constant purging of the back overflow.


Edit: but like I said that's how I interpreted what was said above which could be wrong. I haven't watched the actual BRS video yet.

 

[n8n]

Yes - bean's original setup was with a coast to coast and had the siphon and open channels at the same height. An external overflow box allows for some changes in the configuration.

The siphon can be anywhere at or below the open channel level. (I suppose it could be above, but you may encounter difficulties starting up, and there's no reason I can think of to do so.) There is no reason it can't be 12" below the open channel if your overflow allows; it just needs to stay submerged and maintain a full siphon.

The open channel is at or above the siphon level. As Jason said above, on startup the water level rises significantly higher and approaches the level of the emergency. The typical startup sequence is:

1. Pump turns on. Water starts to flow and the water level in the overflow rises.
2. As the water rises, the siphon channel initially has air in it, reducing the amount of water it can carry. As a result, the water level continues to rise above the normal operating level.
3. The open channel carries the rest of the water. Air in the open channel also limits its capacity and the water level generally continues to rise (this depends on the total flow and the pipe capacities.)
4. The water approaches the emergency drain level, or possibly goes over and stays at this level until the air is purged from the siphon.
5. At this point the siphon capacity increases and drains the water out of the overflow down to its steady state level.

A couple of other details to note:
If the air intake for the open channel gets occluded, it converts to an unrestricted siphon with no gate valve and will rapidly drain the overflow box until it entrains enough air to break the siphon. If the open channel and siphon are at the same level, the siphon will also entrain air. The water level will increase and the system will never start up properly. This is part of the reason the air line is placed above the level of the emergency drain in Bean's original design. Doing so keeps the water level stable at a higher level until air is purged from the siphon.

This placement also means that in case of failure and rising water levels, the order of backup operation is:

1. open channel takes more water
2. dry emergency kicks in
3. open channel airline tubing occludes and converts the open channel to a full siphon.

The setup that BRS uses has a potential flaw in that since the air intake for the open channel is a simple hole, it will occlude and convert to a siphon before the dry emergency kicks in. If the siphon is at a lower level than the open channel, the water may not drop enough to cause an issue and the siphon will still purge air as it should, but that depends on the flow and pipe characteristics. For their setup, the order of backup operation is:

1. open channel takes more water
2. open channel opening occludes and converts the open channel to a full siphon.
3. dry emergency kicks in

So sorry for my ignorance, the siphon level is the top of the elbow of the full siphon ?

So should the open channel ( positioned between the siphon level and emergency ) be optimally placed below / at / or above the regular water line???


Thank you

 

[sleepydoc]

So sorry for my ignorance, the siphon level is the top of the elbow of the full siphon ?

So should the open channel ( positioned between the siphon level and emergency ) be optimally placed below / at / or above the regular water line???


Thank you

For a 'classic' setup, like bean originally described, the water level in the overflow is about at the middle of the horizontal section of the open channel pipe (and the siphon pipe, since it's at the same level.)

Since it's a siphon, the water level doesn't matter as long as it's far enough above the inlet to the siphon pipe so vortices don't form that cause it to entrain air. That may be as little as ½", or it can be a foot above the pipe.

Since the open channel handles the 'extra' flow, it determines the steady state water level in the overflow, not the reverse. If the open channel is placed higher than the siphon, the siphon may be completely submerged, but as I said, the water level is typically about half way up the horizontal portion of the open channel pipe.

 

[chatyak]

Sorry I don't but can try later. Though tonight I'm playing with a new skimmer.

Basically as the water rose the air inlet converted the open chanel to a full siphon basically at just the same time the emergency was just taking on water but then the full siphon on the open drained the water out of the back overflow because its not cut back and intune with the return pump like the normal siphon line is. Once purged of all the water the open channel lost siphon and became an open channel again. The water began to rise again and the cycle started all over again.

Reverting back to my airline slightly above the emergency allowed the partial failure of the siphon to fail into the emergency drain and continue on just fine with out constant purging of the back overflow.


Edit: but like I said that's how I interpreted what was said above which could be wrong. I haven't watched the actual BRS video yet.

Thanks for this. Seems pretty straightforward then that we need the airline

1) Above / next to emergency height or
2) A deep overflow with great height distance between drilled hole in open channel vs full siphon pipe

 

[thejuggernaut]

On the BRS system, I think they should have put the emergency line on the center drain and the open channel on the far side. The way they have it setup now, the pipe blocks the bulkhead passing through the thank. Sleepydoc covered it pretty well. The original system didn't allow for you the drains to be at different levels, and left very little room for change. With an external box with extra depth, you can adjust it several different ways. I like for the box to be about 8" tall so you have plenty of room to adjust all the different lines. Another neat thing about running an external box, is that you can fine tune the height of the water in the overflow, by moving the open channel up or down. I would suggest trying out a few different drain heights when you are setting it up using your specific return pump. If done right, it will purge in seconds and the emergency never sees water until both your siphon and open channel clog.

 

[Firochromis]

Hi dear members,

Do you see any problems using this plumping in the system whime the main tank has BeanAnimal drain system? Main tank has 1.5" pipes and BH, other tanks have 1" pipes and BHs. My return pump is a Red Dragon 10m3.

Regards

 

[n8n]

For a 'classic' setup, like bean originally described, the water level in the overflow is about at the middle of the horizontal section of the open channel pipe (and the siphon pipe, since it's at the same level.)

Since it's a siphon, the water level doesn't matter as long as it's far enough above the inlet to the siphon pipe so vortices don't form that cause it to entrain air. That may be as little as ½", or it can be a foot above the pipe.

Since the open channel handles the 'extra' flow, it determines the steady state water level in the overflow, not the reverse. If the open channel is placed higher than the siphon, the siphon may be completely submerged, but as I said, the water level is typically about half way up the horizontal portion of the open channel pipe.

Ok, so I have a 210g tank i'm filling with water with an external overflow that is about 1/2 the tank (its not quite coast to coast). I've got a box of extra pvc incase i messed one up.

Since its black on black i wrapped the pipes in some papertowels and blue painter tape. They are dryfit to the bulkheads I and i want to glue them in but I want to be 100% extra sure i don't mess them up and have to buy a new bulkhead (i don't have extra bulkheads but i do have extra pvc).

The center one i'm like 99% sure is correctly placed. Basically as low as I could get it and still remove the little strainer i have on it.

The right hand one i'm thinking is either correctly placed, or perhaps should be lowered 1/2 an inch.

The left one is the one i'm really struggling with. So does the entire pipe need to be submerged to achieve full syphon during an emergency? [i obviously will hook the airline directly above the waterline once i get this done], also where will my waterline be? at the bottom of the white on the pipe that i wrapped or in the middle?

If i had the choice i'd like the waterline maybe halfway between the bottom of the overflow and the top of the overflow.

Here are pictures:





Thank you very much, i really want to get this right.

Nathan

 

[jason2459]

FYI, I dry fit my pipe into the bulkhead on top in the back overflow. I glued the rest together except my emergency is a straight pipe up as seen in the picture I posted recently. I also don't have any strainers. I'll defer to someone else on if the heights are right. I'm not a good judge by looking at that picture I don't think. But I can tell you the open channel does not have to be fully submerged to create a siphon. I've tested that recently and when I first setup the BA several moons ago.

 

[n8n]

Ok, so I have a 210g tank i'm filling with water with an external overflow that is about 1/2 the tank (its not quite coast to coast). I've got a box of extra pvc incase i messed one up.

Since its black on black i wrapped the pipes in some papertowels and blue painter tape. They are dryfit to the bulkheads I and i want to glue them in but I want to be 100% extra sure i don't mess them up and have to buy a new bulkhead (i don't have extra bulkheads but i do have extra pvc).

The center one i'm like 99% sure is correctly placed. Basically as low as I could get it and still remove the little strainer i have on it.

The right hand one i'm thinking is either correctly placed, or perhaps should be lowered 1/2 an inch.

The left one is the one i'm really struggling with. So does the entire pipe need to be submerged to achieve full syphon during an emergency? [i obviously will hook the airline directly above the waterline once i get this done], also where will my waterline be? at the bottom of the white on the pipe that i wrapped or in the middle?

If i had the choice i'd like the waterline maybe halfway between the bottom of the overflow and the top of the overflow.

Here are pictures:





Thank you very much, i really want to get this right.

Nathan

So it filled up the overflow as expected but the full syphon never started. I think I read somewhere a fix is to shorten the pipe in the sump.

Anyways I pulled out the plumbing in the overflow for the main drain and it immediately emptied to the sump. I put the strainer over the bulkhead and turned down the gate and it seems like it's working. I blocked the main drain and everything worked flawlessly. I think I'm going to leave main drain open bulkhead with strainer over it.

Thanks

 

[jason2459]

You don't want the drains very deep at all in the sump. Mine are just barely underwater.

 

[Swope2bc]

So it filled up the overflow as expected but the full syphon never started. I think I read somewhere a fix is to shorten the pipe in the sump.



Anyways I pulled out the plumbing in the overflow for the main drain and it immediately emptied to the sump. I put the strainer over the bulkhead and turned down the gate and it seems like it's working. I blocked the main drain and everything worked flawlessly. I think I'm going to leave main drain open bulkhead with strainer over it.



Thanks

It looks like everything is a bit high to me, someone with more experience will hopefully chime in but aren't all three supposed to be bellow the overflow weir?

 

[jason2459]

It looks like everything is a bit high to me, someone with more experience will hopefully chime in but aren't all three supposed to be bellow the overflow weir?

Mine are as the back overflow as a whole is below it as well. Butt up to the trim.

 

[n8n]

You don't want the drains very deep at all in the sump. Mine are just barely underwater.

This is my sump setup. The bean animal is color coded in back and in sump. The coiled hose is connected to salt water mixing station in garage. I have a new skimmer on order and some other stuff to move from old tank.

[

 

[jason2459]

How far into the water are the drain lines? I can't tell by that picture?

 

[n8n]

How far into the water are the drain lines? I can't tell by that picture?

Maybe 7 inches lol. Like I was saying with the bent pipe I don't think it can get to full siphon. If I leave it straight pipe it can. As weird as it so however if I close the main pipe the secondary can get to full syphon even though drain is same depth.

Either way it's silent, if I close off the main the secondary works. I'm pleased with water line. I think I'm going to leave well enough alone. Probably leave them dry fit in overflow for awhile and then decide later if I really want to glue them in overflow.

Thanks

 

[jason2459]

If that's running in that picture I would just remove those pipes and that's about how much depth mine run in. No more then a 1/2"

 

[Floyd R Turbo]

I second that. The bulkhead in the pic above is far enough under water to initiate and maintain the siphon, you don't need (or want) the pipe inserted into it.