Correct piping diameter overflow (BeanAnimal)

[Rene2322]

A few years ago I set up a small aquarium. A practice tank in preparation for a larger reef tank in the future. I now have a wife and newborn baby, so the new tank has fallen in priority. Instead of a new tank, I now want to make a few adjustments to the current one.

I made a mistake with the original piping and I was hoping I can make a correction / adjustment without taking it all apart (a part of the piping is out of reach).

The scenario:
I converted a Juwel Rio 180 with an internal overflow box and 3 bulkheads (DN32 / 1¼") drilled at the back of the aquarium. This resulted in a gross content of 190 liters (50 gallons).

The aquarium drains through the three bulkheads and three separate pipes (and three ball valves) into the sump below (ending slightly below waterline). The sump is a 60 liters aquarium with 2 unequal compartments separated with a baffle. The large section is an illuminated DSB with algae on top. The other section is the return chamber with a return pump (3000 l/h / 792 GPH) and some sensors.

The size of the PVC is determined by so called "running darts". My fault...

It turns out that my pump (with 1,2m head) only give me about half the flow. It looks like my piping isn't in range with the return pump capacity. With the valve of the "full siphon" line correctly adjusted, my system is perfectly silent. But when restarting the system it takes about 10 minutes to purge all the air out. Resulting in an awful amount of splash in my little sump cabinet.
When I do the math, DN20 (¾") had been sufficient (also with bio fouling). So I need to increase the flow to get rid of the air faster.

So how to correct...?

1. Redo the whole piping => no option because a part is out of reach without moving the aquarium. Moving = tearing down = end of hobby for now.
2. Install a bigger return pump (or add a second pump) => no option because this gives too much flow in the sump and also results in a lot of noise at the overflow baffle in the sump.
3. Add an adapter ring in the bulkhead so the pass area at the start of the overflow line is only DN20 (or DN25) instead of DN32. => could be an option, but will this be sufficient, or do I need to also reduce the lower end of the line? I'm afraid that reducing halfway through the line can lead to a blockage.

Who can say something meaningful about this?
Thanks in advance, René

 

[reefteaser]

Your description is a little confusing, pics would help. You have 3 drains for a 50 gallon tank? One should be sufficient. The other two pipes could be used for a bean/animal setup or a two pipe herbie with a return line. Everything could be hidden. I'm assuming your return now is over the tank rim.
If you need some info on the herbie or bean/animal set up this link is extremely helpful: https://gmacreef.com/

 

[Rene2322]

Thanks for responding.

I'm sorry for the confusion. I have 3 drains because I wanted a silent aquarium. I opted for the principle of the Silent Fail Safe Overflow described by BeanAnimal.
It has been running fine since the build eight years ago.

It only is not as "set-and-forget" as intended. A little fouling of the pump, or drain results in a "disrupted" system. I often have too readjust the ball valve of the full siphon drain. The margin for error is very small, I think because of the diameter of piping choosing too large (but maybe I'm wrong).

Attached an artist impression of my system. I hope this clarifies things.

 

[reefteaser]

I see, you've already got the B/A in place. A review of the previously attached articles might still help you identify a flaw and or solution to your set up.
You said the drain into your sump is just slightly below the waterline. "œSlightly below" is a bit ambiguous. Is there any room to reduce the depth of the drain? Perhaps that's the problem with purging the air, where the drain is too deep. Also, the straightest route possible to the sump is best.
If a larger pump is still an option, you could consider a dc pump with a speed range that would help you to dial in the right amount of flow.
Just some guesses on my part. I've been using a herbie set up for quite a while, and it rarely needs adjustment. Usually it's a sign the pump needs a cleaning.

 

[mcgyvr]

It seems like any "option" that will actually help is something you can't do so its really not an option..

I think I would just do something in the sump area to mitigate the effects of the splashing in your sump.. Maybe a lid or something to keep the splashing from getting everywhere you don't want it..

 

[Rene2322]

Thanks for the input.

"slightly below waterline" is about 10 mm (ca. ½"). No change to add air and a minimal back-pressure to purge the air.

Beside the diameter of the PVC in relation to the amount of water flowing through it I can't find any other design flaws. Well, with a new aquarium I will let the drains escape the aquarium at the bottom instead off the back. Also increase the difference in inlet height between the full siphon and the open drain. One thing I have noticed is that the BeanAnimal site is offline. The site gmacreef goes less deeply into this principle.

Anyway, I have bought a new DC return pump with adjustable flow and a little more capacity.

This weekend I will redo tho lower part of my PVC piping. As a test I will route the "emergency drain" and "open channel drain" direct to the "return chamber", so only the "full siphon" will flow through the fuge. I will construct the "full siphon" as straight as possible. A challenge as the space is limited.