Mini or modified Herbie drain on a frag tank

[AForys]

Ok, this frag tank has 1 1” drain with a low profile strainer. I was thinking of adding another bulkhead on the side with a 90 facing up as the emergency drain. The only possible problem I see is the emergency will literally be about 3-4” above the full siphon. Has anyone done a herbie drain with the emergency less then 6” from the main siphon? 

 

Thanks for any input !

[Beer]

It should work fine with less than 6" between the drains. The Bean-Animal setup is based off of the Herbie, but uses three drains instead of two and is typically used in overflows that do not go to the bottom of the tank. There are three drains due to a belief that the emergency drain should be dry and not typically carry water. The system self tunes once dialed in by taking a small portion of the flow to the sump and allowing for variations in flow while maintaining a silent drain. The Bean-Animal overflow typically has only a couple of inches difference between the drain inlets.

 

Are you planning on running the emergency drain dry?

 

As the level in the overflow increases, the siphon rate will increase to a small extent, so it will be able to take small changes in flow, but you won't have a ton of surge capacity with the smaller difference in height if running with a dry emergency drain, assuming you aren't running with the level just below the emergency drain (if you are, there is no surge volume). This just means you are more likely to have noise from you drain if you get a surge volume (as opposed to the normal variances), but I would prefer this anyway as it would alert me to changes in the system more readily.

 

I am setting up a new system and I keep going back and fourth between two or three drain lines. I am using smaller pipe as I don't need that much flow to my refugiua (? plural for more than one refugium? It is in my computer's dictionary, so it is a real word now.), so I built some test drains in a square bucket. At one point I was testing with 1/2" PVC and had the main drain with an elbow turned down with the secondary having the elbow turned up and it was maintaining level fine for the duration of my test. But of course this was not a long term test. I think your main concern with only 2-3" head over an upwards facing drain is sucking in air resulting in a lot of noise. You may want to install 90s or a few 45s to draw from a lower point to avoid air, if necessary. The 45s will provide less restriction, but you will be throttling flow anyway, so the restriction from the 90s shouldn't be too much of a concern.

With your emergency drain, just be sure it is able to flow more than the full volume of your pump and that there is sufficient head space for it to pull a full siphon if that is required for full flow (though not desired).

[ajmckay]

So do you want to have the second drain still inside the overflow box, but coming out the side?  Is your worry about noise from the primary drain?  My experience is that when it's properly dialed in (does take some time and effort) there should be no air sucking or noise.

 

I have a herbie in a compact overflow box as well...  Actually I just built the overflow box from cheap home depot acrylic and spray painted it black.  It's worked great for I think 4 years now...   I have two 1 1/2" drains and the holes are parallel to each other out the back pane and very close.  The openings are definitely not more than 3" apart and there are no issues with sucking at all.  Note that in my setup I run a siphon in the primary and the backup drain stays dry except when an overflow happens.  To date I can only think of a few times where the backup drain has seen any action at all - and I'm pretty sure most of it was just me dialing things in.  I started with a regular ball valve and that was a mistake - it's too coarse an adjustment mechanism.   

 

The PVC elbow I used is a "street elbow" which means it can fit directly into another piece of PVC.  Basically I shaved off all but about 1/4" of the interface from the elbow so I could cram it in the bulkhead...  It's a pretty tight fit still.  Regarding the primary, I've seen people use downward facing elbows but I've also seen some designs that use a sort of baffle that sits in the overflow box and shrouds the primary drain.  It could be shaped like an upside down U and be the width of the box with sections cut out of the ends for water to flow through. 

 

2018-03-02_11-59-22 by aaron M, on Flickr

[AForys]

Thanks for the input guys. Yes my main concern was the full siphon purging since there won’t be much water in the small overflow box. I will be running a trickle like I do in my DT and it’s super quiet!

[ajmckay]

5 hours ago, AForys said:

Thanks for the input guys. Yes my main concern was the full siphon purging since there won’t be much water in the small overflow box. I will be running a trickle like I do in my DT and it’s super quiet!

I think you can make it work as long as you use a decent quality gate valve and spend some time tuning it in.  I would also add that I believe it's also important to have a good return pump.  Over time a pumps output can be reduced with build up so it helps to have something that's not going to get bogged down.  Helps the overflow to be consistent.