External Overflow Herbie Drain Setup

wpeterson

Well-Known Member
BRS Member
I'm plumbing a new tank with an Eshopps Eclipse overflow (medium size, 2x 1" drains). I've drilled/installed two 3/4" return lines and the 1.5" main bulkhead for the external overflow. I could use advice for the actual drain plumbing within the external overflow box.

I am debating whether to install a 180 degree turn like a Durso or leave a straight drain. The official Herbie documentation says a 6"+ difference in height between the siphon and emergency drain is required - which seems to argue for a simpler setup with the drain right in the bottom of the overflow and a riser for the emergency drain.

Which of these two setups looks more correct?

1) Straight drain
2016-05-30%2014.39.28.jpg


2) durso style 180
2016-05-30%2014.31.36.jpg


The rationale for 6" of difference in height seems to be giving yourself room for fluctuating water levels when you're adjusting the siphon drain vs. the return flow. Any advice appreciated.
 
Either could work, but given the space limitation you would want to either go with the first pic (drain in the bottom with no U), or change the second to get rid of the strainer and then lower the upsidown U so that it's just off of the bottom of the box. If you run it as pictured in the bottom/second pic it will need constant adjusting and will still end up using that back up far too often.

The thing with Herbie's is that the water level WILL fluctuate in the overflow box somewhat over time and even day to day. The more difference between the height of the drain and the back up drain, the more the system can tolerate those fluctuations without needing adjustment OR having water start to trickle down the back up. (Side note, the original Herbie himself lets his run that way, with the trickle going down the back up. It makes me nervous, but he's been doing it for years and unless I missed an unpleasant update it's never been a problem/flood.)

IME there is very little if any advantage to running a herbie with the upsidown U on the main drain IF you have the space. You don't have any space to spare, so to me the choice should be clear :)
 
Either could work, but given the space limitation you would want to either go with the first pic (drain in the bottom with no U), or change the second to get rid of the strainer and then lower the upsidown U so that it's just off of the bottom of the box. If you run it as pictured in the bottom/second pic it will need constant adjusting and will still end up using that back up far too often.

The thing with Herbie's is that the water level WILL fluctuate in the overflow box somewhat over time and even day to day. The more difference between the height of the drain and the back up drain, the more the system can tolerate those fluctuations without needing adjustment OR having water start to trickle down the back up. (Side note, the original Herbie himself lets his run that way, with the trickle going down the back up. It makes me nervous, but he's been doing it for years and unless I missed an unpleasant update it's never been a problem/flood.)

IME there is very little if any advantage to running a herbie with the upsidown U on the main drain IF you have the space. You don't have any space to spare, so to me the choice should be clear :)

Thanks, John. I've enjoyed your plumbing and reef keeping advice for many years.

It looks like the first option (short, straight drain with strainer) is the best option. I'll circle back once my sump is shipped and everything is plumbed.
 
I agree completely. That's the advantage to the 3 pipe in the bean animal is the lack of fluctuations in the overflow water height. It's too bad there isn't enough room for that.

Sort of makes me wonder why herbie uses a dry emergency pipe instead of a durso with a small constant flow through. Simply turning the air intake to be near the water level would act as a failsafe. Meaning when the water level rose due to a clog in the main siphon the water would "close" the air intake turning the durst into a second siphon and would suck the water level to the level of the air intake. It would repeat all day until you heard the noise and corrected the clog. Also the durso would enable easier adjustment of the siphon because the durso at 3/4 handles between 0 and about 350 gph. Making the adjusting more forgiving.

I'm not saying you should do this. Just thinking out loud
 
Thanks for weighing in on the factors here. My last system used a Herbie setup with a nicely tunable gate valve that let me dial in the water level for stability and no audible flow through the emergency drain. Generally, if the strainers or other infrastructure became clogged and the flow dropped through the siphon I would have to intervene every 3+ months or so - either to clean out the obstruction or tune the drain to silence again for the new flow rates. I generally breakdown and swap return pumps every 3-6 months anyway, so it's a good excuse to re-calibrate with maintenance.

The major difference with this external overflow box vs. the DSA 90gal center overflow is space and tolerance for fluctuating water levels. The traditional in-tank overflow was 26" high and I cut my drain pipes to intake 6-8" below the weird for the main siphon and the emergency drain right at the weir. I think using the main/emergency drains as simple floor/ceiling almost as tall as the small overflow itself (7-8" tall, so 6-7" of working water level to tune) makes sense here. I could conceivable apply a durso to the emergency drain, but I would either be sacrificing vertical room to maneuver in terms of water level or bumping up the plumbing above the ceiling of the overflow, which would prevent putting the cover on.

I'm hoping to keep the overflow covered both to keep light/algae down and for noise levels.
 
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