That's an interesting thought. I thought all Bean Animals had a trickle overflow (Mine does) Has there been any reports on RC on nitrate buildup based on this? How would nitrates build up in the pipe? Mine has a constant, but very minimal flow going down the trickle pipe.

I still think you could do it my way. :)

My Bean Animal has a trickle and you would be surprised how much flow comes down the trickle. The key is that it all comes down the sides...that can be a lot (in my case it is) and yet everything is safe and dead silent. It even falls an entire floor for me. I think the above idea would be the best way to go. Full and emerg on one end, trickle and emerg on the other.
Obviously the trickle isn't going to do a lot to surface skim, but it can be greater than you think. What size are the holes?

Am I totally out to lunch thinking that normal internal overflows (top to bottom) with two holes shouldn't be used as a beananimal?

I just think that with 24"-ish height of the overflow, and very minimal flow going into the overflow itself, there would be detritus buildup at the bottom of the overflow.

Realistically all three pipes should be in the same overflow.

Of course all of the bean animal setups have trickles... but in the same overflow! (I'm sure you only have one overflow with 3 pipes in it)

You would be correct. If most of the flow was then going down the full siphon side, there would be minimal turnover on the trickle side. I am not sure if this would cause enough of a problem that nitrates would buildup as it would still surface skim just at a really slow rate. I would be interested to see this in action.

So what if you put the trickle in the same side as the siphon and essentially only surface skim from one side and raise the overflow height in the other side a bit and turn it into an emergency side or

Have two full siphons with trickles and forget the emergency. Would also have to forget about combining any pipes below as full siphons cannot be connected to anything else.

This is why I hate multiple overflows. I prefer one big external.

If you made each overflow have a full siphon there would be no detritus buildup and full surface skimming. they could have strainers and be at bottom of overflow, (no stand pipe). there would be good water turnover and any detritus would end up in the sump/skimmer.

if the return pump ever failed you would only need enough volume in the sump to handle the volume of the overflows

Thanks for the responses guys!

To answer the main questions - yes, I only have two holes per overflow, and one of them is dedicated for the return line back to the tank, so only three holes to play with getting water in to the sump. I might be able to re-jig the return line and run it up the side of the tank in the joist space in the wall, but I'm not confident I can do that with the amount of access I have in there now.

And I'm not really thrilled with the idea of just separating the pipes to have two separate dursos, as it is now it works just fine for what I need it for, the problem is the mice-bubbles durso's produce. The water in my sump travels in a giant U, it enters and exits the sump on the same side. I didn't realize when I designed it that for a small amount of the water (and thus bubbles), they're able to "turn the corner" between the entrance and exit really tightly which doesn't give the micro-bubbles enough time to float to the surface. Hence the filter socks that I have to change every 24 hours.

I also don't think I'd be OK with going back to a Herbie - in principal they work fine, but I've got a super sized auto-top off pump to bring water all the way up from my basement, and a smaller-than-it-should-be return chamber, so the water level in the return chamber fluctuates a little bit on it's own anyway. My experience with the Herbies if they're not tuned properly is that can lead to a gradual over-filling of the display tank.

I hadn't really thought about the amount of build up that would happen in the trickle only overflow.... hmmmmm. Oh for the power of foresight! Changing the plumbing on this beast is not going to be a small job, perhaps I'll just live with what I've got if the general consensus is that an bean-animal style would be sub-optimal in this arrangement.

If it was me I'd run the return separate (not through the overflow) allowing the 4 holes to be used for the drain system and realistically better options for the return as well.

The four drains setup as follows:

The smaller hole from each overflow, tee together then to a single gate valve, from there to desired sump section, this would be the primary drain. This primary drain will be the full siphon, so extend a pipe in the overflow towards the surface as needed to prevent the overflow from draining completely during shut down. Just don't make it too close to the surface otherwise you'll get a vortex and introduce air into the drain. The single gate valve will actually allow better constant control over two separate valves as the flow rate to each overflow may not be constant but the overall flow rate will be. Hence with two gate valves, one for each overflow, you'll constantly be fighting with them to reach equilibrium only to discover it's not possible.

The two large holes again can be tee together to the desired sump section, or they can be maintained separately. Use standard durso standpipes for each hole, setup just slightly above the desired overflow water level or at the level they will receive a slight trickle at optimal overflow level.

Adjust gate valve so the dursos receive a little water for best results, it will allow more freedom and less constant tinkering. The result is a cross between a herbie and a bean animal, after all when it comes down to it the bean is just a herbie with an extra standpipe, really the same concept. The advantage here is both overflow boxes will get used so no dead zones, two dursos act act as back up which should handle full flow during primary clog. Using actual durso standpipes rather than straight pipes for back up allows the ability to send some flow down them without major noise issues and if the flow path changes some how there is extra freedom to prevent the need for adjustment.

My thinking is ...

There's no way you could ever incorporate a Bean Animal into your setup as you have 2 boxes, and the original design is based on the amount of water in just 1 box

Is there any way you can redo the drain plumbing so the 2 'main drains' each go direct to the sump, and still have the 4th hole for an emerg ?
This would save you redoing your return line
I know it'll be a dialling nightmare, but once balanced, it shouldn't need much tuning

Then you could put 'high level' floats in your boxes to shut off your return pump in the event your emerg is beyond it's 'safe' level

I know mine is not the same setup, but I have a float a bit above my Herbie emerg so it shuts the pump down before the trim can get wet
And the float is never wet, so it should last forever

I hope some of this helps

Been running a Herbie trouble free with dual overflows and float valve ATO for about 3 years now without any problems.

One chamber is my primary, other the emergency where I flow a trickle. No microbubbles even at about 1000gph and ATO keeps level in the sump to about 1/8".

To convert from the twin Dursos basically only needed to remove them from the standpipes they were on, add the gate valve and some playing with a sump baffle and drain line length in my fuge.

Just saying Herbie could work.