Help with external refugium plumbing

[deutchriffer]

So I got a custom made external refugium have it fed by an AI AXIS 40 and overflows back into the sump. trying to get this thing going but I think I have some kind of physics problem I haven’t planned for.

You see in these photos the return and overflow lines are the same height, the return elbows down with siphon break holes drilled, the overflow originally had the spray bar installed and I’ve since removed thinking that was the issue but even with no obstruction it still seems to only trickle down the overflow and no matter the speed of the feed pump, it still fills the reservoir faster than it drains

If it were a hole size issue I would presume I would just see it not being able to keep up, but it’s just a slow trickle..absolutely baffled.

Things I have tried

I tried orientating the overflow elbow down, and toward the front

I tried to stick 1/4 RO rube into the fitting to see if it is some kind of air pocket and it seems to help a little but then when increasing the flow it seems to hinder the overflows ability given that it is consuming space in the bulkhead

I tried to feed the same pump that feeds the fuge, into the overflow line where it enters back into the tank (assumed this might work like those python hoses) but still just doesn't seem to be making much difference

 

[twentyleagues]

So the clear lines are the drains?
You seem to be working against gravity here. Lifting the fuge up 6-10" would help imo.

 

[KStatefan]

What is inside the fuge for the overflow?

I have a simular set up that has a slotted weir for the overflow then I added a full siphon to take some of the flow as it made to much noise it it all went thru the weir. Total flow is about 100 gph on mine.

 

[deutchriffer]

I had a slotted weir I was thinking that contributed to the problem so I just went a single elbow to test it.

Wondering if I should increase it from 1/2” to 3/4”

 

[KStatefan]

I had a slotted weir I was thinking that contributed to the problem so I just went a single elbow to test it.

Wondering if I should increase it from 1/2” to 3/4”

I think mine is 1". It came with a air hole in the top of the 90 degree fitting from Lifereef.

 

[deutchriffer]

I think mine is 1". It came with a air hole in the top of the 90 degree fitting from Lifereef.

Just making sure I’m understanding this right, you have a hole to release air within your bulkhead?

At the moment I am using these bulkheads, https://newlifekeys.com.au/grey-din-90-degree-tank-fitting-bulkhead/

I’m wondering if I’ll see any difference in using a straight through fitting rather then the elbow on the drain.

In regards to lifting the fuge, unfortunately I’ve designed it in a way where everything fits quite snug (not the smartest move in hindsight)

I don’t even know how useful the thing will be to me in the long run I just figured extra water volume, and a fuge could be beneficial.

If I can’t get this running with higher flow than I have, then I may to look at repurposing it as a stupidly expensive ATO reservoir

 

[KStatefan]

Just making sure I’m understanding this right, you have a hole to release air within your bulkhead?

At the moment I am using these bulkheads, https://newlifekeys.com.au/grey-din-90-degree-tank-fitting-bulkhead/

I’m wondering if I’ll see any difference in using a straight through fitting rather then the elbow on the drain.

In regards to lifting the fuge, unfortunately I’ve designed it in a way where everything fits quite snug (not the smartest move in hindsight)

I don’t even know how useful the thing will be to me in the long run I just figured extra water volume, and a fuge could be beneficial.

If I can’t get this running with higher flow than I have, then I may to look at repurposing it as a stupidly expensive ATO reservoir

Hole in the 90 degree fitting blue circle below.

 

[deutchriffer]

Yeah I’ve drilled one in mine too, apparently it can be an issue if you don’t but I would’ve expected to hear gurgling if that was my issue.

Someone mentioned soft tubing can have this kind of trick effect too, I’m not sure how true that is?

Really hope there’s something I can do that doesn’t involve raising the fuge.

As it stands the flow is likely too low to be doing any good

 

[deutchriffer]

Bump, curious if there’s any validity to soft plumbing causing issues with air pockets?

Also wondering if I should just step the hole up to 32mm/1” or if I’m better trying hard plumbing the existing bulkhead or getting rid of the elbow and trying a straight through bulkhead? In my case it’s not a simple removal of the elbow, as the elbow forms part of the bulkhead.

Any guidance would be much appreciated.