Refugium Drain Question

[tymo92]

Relatively new tank, I have this refugium plumbed with a gravity drain to the return section of my sump. When I first filled up the fuge (fed from a return manifold) it wasn’t draining, which freaked me out about future flood risk.

I was able to get the drain to function after a second try but now I’m worried as I didn’t think about any risk of the fuge not draining other than the inlet getting blocked.

Any ideas why it wouldn’t consistently drain? Refugium outlet is about 6” higher than sump water level. 1/2” pipe and the drain in fuge definitely wasn’t blocked.

Pics below of the fuge and where it enters the sump (back right corner)

 

[UncommonSense]

My immediate guess is the plumbing; you got an air bubble trapped in there!

Drains like to go downhill, and struggle to push out air bubbles if they have to push them significant distances underwater!

Try making your drain plumbing inside the sump a bit shorter, or drilling a 1/4” hole in it right around the water line!

 

[tymo92]

My immediate guess is the plumbing; you got an air bubble trapped in there!

Drains like to go downhill, and struggle to push out air bubbles if they have to push them significant distances underwater!

Try making your drain plumbing inside the sump a bit shorter, or drilling a 1/4” hole in it right around the water line!

Ah, makes sense. So the key is making the drain plumbing in sump just below water line, and/or drill a hole above that for air to escape?

 

[UncommonSense]

Ah, makes sense. So the key is making the drain plumbing in sump just below water line, and/or drill a hole above that for air to escape?

Yup! That will definitely help! Though, it could be wise to add a second drain bulkhead to the refuge with an elbow in it to act as an emergency drain, just in case you have any other oddball issues!

 

[tymo92]

Still having issues with this drain, even when it does flow water it only can handle ~10gph. Is the 1’ stretch of horizontal pipe immediately after the refugium bulkhead a likely culprit? Anything I can do to get more flow out of this?

 

[UncommonSense]

Still having issues with this drain, even when it does flow water it only can handle ~10gph. Is the 1’ stretch of horizontal pipe immediately after the refugium bulkhead a likely culprit? Anything I can do to get more flow out of this?

10gph is unusual! I’m now suspicious that the drain is actually clogged!

Can you disconnect the drain plumbing at that union to check for obstructions?

 

[tymo92]

10gph is unusual! I’m now suspicious that the drain is actually clogged!

Can you disconnect the drain plumbing at that union to check for obstructions?

Have disassembled it, no clogs. I’ve also seen it get a full siphon (not consistently) if the water level rises above the air holes on the intake so I don’t think it’s the pipe diameter that’s limiting it.

I wonder if there is just very little head pressure from this horizontal section, the water isn’t flowing “downhill”?

 

[Quietman]

You essentially have another display tank. The drain will only support low flow unless you want to constantly be cycling between full siphon an nothing (like an old surge tank). You can have very low flow (think your trickle flow drain in a bean animal) that the drain can support or setup a small full siphon and a drain (herbie) or install larger pipe that can handle more flow without going full siphon.

 

[tymo92]

You essentially have another display tank. The drain will only support low flow unless you want to constantly be cycling between full siphon a nothing (like an old surge tank). You can have very low flow (think your trickle flow drain in a bean animal) that the drain can support or setup a small full siphon and a drain (herbie) or install larger pipe that can handle more flow without going full siphon.

Thanks, this is what I’ve come to realize. I’m just surprised at how little flow the drain with air (durso equivalent) can handle without overflowing the fuge. I’d rather not being running only 10gph flow to the fuge and have to add another powerhead to it for circulation. And running higher flow and relying on the drain to cycle between full siphon/nothing makes me nervous the siphon wouldn’t start and would overflow the fuge.

 

[UncommonSense]

Have disassembled it, no clogs.

Surprising!

I wonder if there is just very little head pressure from this horizontal section, the water isn’t flowing “downhill”?

Lack of head pressure, length of horizontal pipe, and pipe diameter all play into the equation here!

I still think this can work with a second bulkhead added, possibly lower than the first one, in at least 3/4”… possibly swap the top bulkhead for 3/4” too?

Note; not all bulkheads are created equal! — some require a significantly larger tank hole size for a same-sized pipe fitting, and some are extremely compact!

 

[Quietman]

Oh the siphon will restart if it's setup correctly. Those old surge tanks had the pipe on a u-bend deep in the tank so when the siphon started it ran until it hit the bottom of the drain pipe.

It also will sound like a toilet flushing every 5 min but you know it's always working. :)

10 gph flow in a refugium can work very nicely as you don't need really high flow to control nutrients or provide water to refugium livestock and plants. Most find a separate small powerhead in a refugium very beneficial if you have the big ball o'cheato. If not, then you might not need it.