Herbie on dual overflow

[vbsaltydog]

I have run herbie overflows before so I understand the design/results. My posting is to hear opinions on the Herbie in a dual overflow environment.

The only drawback to a Herbie overflow is that it takes two drain lines and since "reef ready" tanks are only bottom drilled for two lines, you must either run your return line over the back of the tank or drill a new hole for the return.

While this is unavoidable in tanks with a single overflow, what about dual overflows?

Since a 1" drain at full siphon pulls MUCH more water than with a 1" durso standpipe, it is safe to say that a single Herbie is sufficient to replace two Durso's as far as flow is concerned. If this is true, what drawbacks are there (if any) to running the full siphon line in one overflow and the open/emergency drain in the other overflow, leaving the stock return lines unmodified and in use as returns?

It seems to make perfect sense but I have never heard of anybody doing it.

 

[wildman926]

I am running exactly what you described. A full siphon on one, with another drain slightly taller and fully open as a back up. It works great. This is on my overflow box. Dead silent.

 

[vbsaltydog]

I was referring to built-in (drilled) overflows but I suppose overflow boxes apply. Thanks for the reply.

 

[ghostman]

I run a Herbie in a dual overflow. The problem that I see with your setup is that the overflow with the emergency drain will not have any flow under normal conditions, and the water will be stagnant in the overflow.
My Herbie is a dual Herbie, with 2 siphons and 2 emergencies. It is a little harder to tune initially, but not brain surgery. My returns are over the back sea swirls.

 

[tankmates]

I have herbie on my dual overflows, with one being full siphon and second in other overflow as emergency. This is exactly what i am facing now, water is becoming stagnant in overflow with emergency. To make matters little complex is that in each overflow, i have 1" drain and 3/4" return. I am looking to change that plumbing to have one return only and use second return as siphon (3/4") with 1" being emergency on that overflow, so will have 3 drains and one return

 

[vbsaltydog]

@ghostman

In a normal Herbie, the open drain should always be processing the minimal excess that the siphon can't handle, hence the equilibrium. Did you ever try a single Herbie split over dual overflows or did you go straight to dual herbies?

 

[vbsaltydog]

I have herbie on my dual overflows, with one being full siphon and second in other overflow as emergency. This is exactly what i am facing now, water is becoming stagnant in overflow with emergency. To make matters little complex is that in each overflow, i have 1" drain and 3/4" return. I am looking to change that plumbing to have one return only and use second return as siphon (3/4") with 1" being emergency on that overflow, so will have 3 drains and one return

Hhhhmmm... so a "bean animal" essentially.

 

[ghostman]

I had a Herbie in a single overflow on a 120g that worked flawlessly.

 

[Mike S]

I went through this decision process a few months ago with my dual overflow tank with only 2 holes per overflow. One option was to put a siphon and an emergency drain in each overflow and bring up the return over the edge of the tank. I have screens for my wrasses so that wasn't really an option. I ended up with one siphon and an emergency drain in one overflow and one siphon and the return piping in the other. The two siphons are teed together and controlled by one gate valve. This arrangement has worked out perfectly. The only thing to consider is if the emergency drain can handle the entire flow that your return pump puts out if the siphons ever clog. I can close my gate valve and my emergency does fine with the 600 gph going through my system. Be sure to screen of the drains so snails and other critters dont clog your lines.

 

[vbsaltydog]

For those that have a single siphon and single open drain in dissimilar overflows that are getting stagnant water in the open drain overflow, why not just increase the choke on your siphon, sending more flow to the open drain overflow? or am I missing something?

In a herbie/bean animal, you are meant to choke the siphon so that some of the return flow spills over to the open drain, but not enough to make noise. That should resolve any stagnant water issues near the open drain.

Please correct me if your personal experience has taught you otherwise.

 

[wildman926]

choke the siphon so that some of the return flow spills over to the open drain, but not enough to make noise. That should resolve any stagnant water issues near the open drain.

That is how mine works in my overflow box in the pic above.

 

[krzyphsygy]

Does anyone have any pics of there Herbie designs??

 

[perverseosmosis]

I went through this decision process a few months ago with my dual overflow tank with only 2 holes per overflow. One option was to put a siphon and an emergency drain in each overflow and bring up the return over the edge of the tank. I have screens for my wrasses so that wasn't really an option. I ended up with one siphon and an emergency drain in one overflow and one siphon and the return piping in the other. The two siphons are teed together and controlled by one gate valve. This arrangement has worked out perfectly. The only thing to consider is if the emergency drain can handle the entire flow that your return pump puts out if the siphons ever clog. I can close my gate valve and my emergency does fine with the 600 gph going through my system. Be sure to screen of the drains so snails and other critters dont clog your lines.

I'm in the exact same boat and trying to figure out what to do. I got to wondering though:

How do you keep the water level at a consistent level in the overflow compartment that contains the return and siphon? Isn't this the same as trying to match the output of a drain to the input of a return?

 

[vbsaltydog]

I'm in the exact same boat and trying to figure out what to do. I got to wondering though:

How do you keep the water level at a consistent level in the overflow compartment that contains the return and siphon? Isn't this the same as trying to match the output of a drain to the input of a return?

The Herbie physics still apply. You choke of the siphon(s) so that the total siphoned drain volume is a little less than what the return pump sends up. This causes the water line inside of the overflows to rise high enough to drain down the open drain(s) but the volume is not enough to cause the open drain(s) to slurp.

The open drain is where the constant water level is maintained. The return volume will vary slightly based on the return pump performance variables, barometric pressure, etc. but the slight changes in the return volume are handled by the open drain so they become transparent. The water line will hold where the open drain(s) take on water.

As long as your tank is level then the physics are not changed by the placement or number of siphon drains, open drains, returns.

 

[perverseosmosis]

The open drain is where the constant water level is maintained. The return volume will vary slightly based on the return pump performance variables, barometric pressure, etc. but the slight changes in the return volume are handled by the open drain so they become transparent. The water line will hold where the open drain(s) take on water.

As long as your tank is level then the physics are not changed by the placement or number of siphon drains, open drains, returns.

It makes sense to me that, in a closed system, wherever there is an open drain, there will be a constant water level. I guess what I'm not understanding (yet, and thanks for helping me get there) is this:

1) If a compartment doesn't have an open drain, but instead a syphon, what's maintaining a constant water level? Does an open drain in one compartment affect the water level of a separate overflow compartment? Even if they're not "connected"? Is this the magic of Herbie physics ?

2) If a compartment does have an open drain, what keeps it from taking on so much water that it gurgles? The return volume is going to be split evenly across both overflow compartments. It seems like I'd have to limit the total return volume to only twice that trickle.

 

[DownwardDawg]

I run a Herbie in a dual overflow. The problem that I see with your setup is that the overflow with the emergency drain will not have any flow under normal conditions, and the water will be stagnant in the overflow.
My Herbie is a dual Herbie, with 2 siphons and 2 emergencies. It is a little harder to tune initially, but not brain surgery. My returns are over the back sea swirls.

This is exactly what I'm plumbing right now. I'm just tee-ing the 2 drains together at the sump with one gate valve just after the tee. My returns are over the back sea swirls also.

 

[vbsaltydog]

1) If a compartment doesn't have an open drain, but instead a syphon, what's maintaining a constant water level? Does an open drain in one compartment affect the water level of a separate overflow compartment? Even if they're not "connected"? Is this the magic of Herbie physics ?

2) If a compartment does have an open drain, what keeps it from taking on so much water that it gurgles? The return volume is going to be split evenly across both overflow compartments. It seems like I'd have to limit the total return volume to only twice that trickle.

You are pushing water into both overflows at the same rate, what one overflow gets, so does the other (assuming your tank is level). That being said, there is no difference between a single overflow and dual overflows.

You are wondering why the overflow with the siphon doesn't "run dry" while flooding the overflow with the open drain since the overflow with the siphon "drinks" more water than the overflow with the open drain does but for every drop that is "drank" by the overflows, a drop is returned to the display and thus, spilling into an overflow. This maintains the balance.

If the water returned to the open drain overflow at the rate that the siphoned drain overflow drained then it would flood. If the water returned to the siphoned drain overflow at the rate that the open drained overflow drained then it would constantly run dry and then re-establish the siphon. This doesnt happen because the water is returned to both overflows at the rate that it is drained from both overflows.

Think of it as pushing water down in one overflow causing it to rise in the other, and vise versa. You aren't ever changing the total volume of water in the system, you are just displacing it. The siphoned overflow displaces water faster than the open drain overflow does but they never change the total water volume in the system so the water line is maintained.

 

[perverseosmosis]

So things do equalize across compartments. Would this work then?


[o O] [O o]
.1.2...3.4


1) Return pump
2) Open drain
3) Syphon
4) Return pump

It's Herbiean in that there's only 2 drains. If I understand you correctly, the level in the overflows is established by the height of 2.

I suppose a BeanAnimal approach would swap 1 with an emergency drain.

 

[vbsaltydog]

So things do equalize across compartments. Would this work then?


[o O] [O o]
.1.2...3.4


1) Return pump
2) Open drain
3) Syphon
4) Return pump

It's Herbiean in that there's only 2 drains. If I understand you correctly, the level in the overflows is established by the height of 2.

I suppose a BeanAnimal approach would swap 1 with an emergency drain.

That should be fine and yes, (2) sets the water level.
IMO bean animal's approach is overkill.

 

[perverseosmosis]

Thanks for all your help! I can't wait to try it out.