Emergency Drain Height on Herbie Style overflow

rob taft

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I'm new to sumps so forgive the question.

How far above or below the Weir does one place the emergency drain on a Herbie style overflow? I've seen where some place the drain opening about a 1/2 of so below the weir thereby allowing some amount of water into the sump and other placing it just above the weir so it won't receive any water unless the water rises in the overflow. My thought are to the latter and not the former i.e. but I've seen both advised
 

homer1475

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I have mine set to set the water height in the tank. I have a rimless tank and like the water level high. So the height of my emergency dictates the height in my display(center tower style overflow).

I also do not like the sound of crashing water, so the higher my emergency, the less fall into the overflow the water has.

I don't think either way is wrong, it's just what you prefer.
 

Montiman

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I'm new to sumps so forgive the question.

How far above or below the Weir does one place the emergency drain on a Herbie style overflow? I've seen where some place the drain opening about a 1/2 of so below the weir thereby allowing some amount of water into the sump and other placing it just above the weir so it won't receive any water unless the water rises in the overflow. My thought are to the latter and not the former i.e. but I've seen both advised
I find it pretty much impossible to tune a herbie with out some flow through the secondary drain. That being said if some flow is going through the secondary drain a better question is where do you want the water level in the overflow box as the height of the secondary drain is what determines the water level.

I have found that I want the water level in the overflow box to be just below the weir teeth. if the water level is above the teeth it will reduce the surface skimming from the weir. The lower the water level in the overflow box the more noise comes from water falling down the overflow box. Thus I like the water level in the overflow box as high as I can while still being slightly lower than the weir teeth. Since this is where I like the water level this is where I like the top of the emergency drain.
 

homer1475

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I find it pretty much impossible to tune a herbie with out some flow through the secondary drain. That being said if some flow is going through the secondary drain a better question is where do you want the water level in the overflow box as the height of the secondary drain is what determines the water level.

I have found that I want the water level in the overflow box to be just below the weir teeth. if the water level is above the teeth it will reduce the surface skimming from the weir. The lower the water level in the overflow box the more noise comes from water falling down the overflow box. Thus I like the water level in the overflow box as high as I can while still being slightly lower than the weir teeth. Since this is where I like the water level this is where I like the top of the emergency drain.
Said much better then I did, but basically how I do it to.
 

ca1ore

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Noise is an issue, but you ought to also consider emergency capacity. If you have the latter too high up, then there may not be any room for head pressure to build up and the emergency will fail to handle all your flow in the event of a major problem. A way around this is to upsize the diameter of the emergency stand pipe. Probably nothing to be done about the size of the bulkhead, but I always use adapters to get at least two PVC sizes larger. On my current tank, the emergency is a 3" standpipe over a 1 1/2" bulkhead. You may never need 100% from the emergency, but having one that cannot handle that much rather defeats its purpose.
 

newbie2014

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Do you suggest having a gate valve on. Other the main drain and the e-drain?

The seasoned reefers can probably guide you better.........

Eventhough I've been reefing for a few years, I just started my first tank-sump setup as of this January. It's a rimless 60g cube with single drain (durso) corner overflow. I converted it to a herbie with 1" main drain and 1" emergency drain. The main drain stands about 12" and the emergency about 1/4" below the overflow weir, respectively. I put a gate valve on the main drain to regulate the height of the water in the overflow.
 

piranhaman00

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Noise is an issue, but you ought to also consider emergency capacity. If you have the latter too high up, then there may not be any room for head pressure to build up and the emergency will fail to handle all your flow in the event of a major problem. A way around this is to upsize the diameter of the emergency stand pipe. Probably nothing to be done about the size of the bulkhead, but I always use adapters to get at least two PVC sizes larger. On my current tank, the emergency is a 3" standpipe over a 1 1/2" bulkhead. You may never need 100% from the emergency, but having one that cannot handle that much rather defeats its purpose.

Heed this knowledge!

I was just watching my tank that has been set over for over 1 year and I have left for multiple vacations. I left for 5 mins and came back and the tank had overflowed and water on floor and on stand. Thankfully , apex leak detector killed pumps, only about 3 gallons of the 175 gallon system made it to floor.

Turns out a new small tang went down the main drain and got stuck perfectly to block the water almost completely.

Anyway, I’m completely dumbfounded by what happened, why did E drain fail!? Well after plugging pumps on and off to watch tank start to overflow , the water would rise to the E drain and start to go down but it couldn’t rise high enough to fully drain and the tank water started to rise to match the E drain, resulting in overflow.

Lesson learned, do a practice main drain clog by closing gate valve and make E drain lower than tank max water level! Kinda duh but didn’t think of that.

Also I saved the tang but I had to cut up my plumbing and pull him out after flushing the pipe with RODI , he was very stunned by Alive this morning!
 

Montiman

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Heed this knowledge!

I was just watching my tank that has been set over for over 1 year and I have left for multiple vacations. I left for 5 mins and came back and the tank had overflowed and water on floor and on stand. Thankfully , apex leak detector killed pumps, only about 3 gallons of the 175 gallon system made it to floor.

Turns out a new small tang went down the main drain and got stuck perfectly to block the water almost completely.

Anyway, I’m completely dumbfounded by what happened, why did E drain fail!? Well after plugging pumps on and off to watch tank start to overflow , the water would rise to the E drain and start to go down but it couldn’t rise high enough to fully drain and the tank water started to rise to match the E drain, resulting in overflow.

Lesson learned, do a practice main drain clog by closing gate valve and make E drain lower than tank max water level! Kinda duh but didn’t think of that.

Also I saved the tang but I had to cut up my plumbing and pull him out after flushing the pipe with RODI , he was very stunned by Alive this morning!
To me the real problem is not big enough drains. I have no idea why tanks used to have 1.25, 1.5 and 2in drains and now every tanks seems to have 1in or 3/4in even when going custom. Yes extra drains provide redundancy, but I have never seen a 1.5in drain clog but I have seen many 3/4in and 1in drains clog. I firmly believe that it is better for safety to go up a drain size rather than increase the amount of drain lines.
 
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