Bubbles from an Overflow...

[Salt1972]

Hey Reefers(?)-

Over the last few days, we've been adding a refugium to our 125g display. Because we have an odd system design / installation, the refugium is located above the tank. So, we located a Jebao DCS2000 in the tank behind the rock work and plumbed it up to the refugium with 1/2" PVC. We drilled a 1" bulkhead in the side of the refugium for an overflow (with a secondary 1" overflow 2" above the primary as a failsafe) back to the display tank.

Here's the problem... the overflow draws air and bubbles into the display tank which are unsightly and will create salt creep. How can we eliminate the bubbles in the overflow back to the display?

Here are some pics to better convey the design and issue. Thanks in advance.

Matt

Below is a closeup of the refugium - no chaeto or grow light yet (I'm thinking a Kessil H80). You can see the primary overflow in the middle left coming out of the front of the fuge. The secondary overflow is on the left side. The input is 1/2" bulkhead on the right.

Below is a view of the refugium above the display. You can see the 1" primary overflow into the display toward the right beside the Kessil. The secondary overflow is 1" vinyl tube toward the left. We intentionally left this short so it would make noise if in use. (ATO reservoir is top right)

Below is an image of the system with the service door up.

Lastly - an image of the system with the service door closed... just to prove that the finished product with the ATO & Fuge above the tank doesn't look as crazy as it sounds.

 

[TheEngineer]

Can you set the water level above the height of your drain bulkhead? You can use a valve to control the flow rate and get it to pull a siphon. Then you shouldn’t get bubbles (unless there are bubbles in the fuge).

 

[Salt1972]

Can you set the water level above the height of your drain bulkhead? You can use a valve to control the flow rate and get it to pull a siphon. Then you shouldn’t get bubbles (unless there are bubbles in the fuge).

Thanks for your help Engineer. Wouldn't I be in a constant state of valve adjustment trying to match input exactly but just over the primary overflow? I'd fear that if I restricted the valve on the primary too much, then we'd be reliant on the secondary overflow. Not enough and we'd be back to drawing air. That's simple to try... just trying to think through options. Again, thank you for your input.

 

[TheEngineer]

It's actually not a terribly delicate adjustment. What you have there is essentially a herbie overflow minus the valve on the primary drain.

 

[TheEngineer]

Here's a reference: http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

 

[Salt1972]

Here's a reference: http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

I just read this article. It is very similar. I'll try the valve. As the article mentions... I am hesitant to run a wet secondary, but I'll try it.

 

[TheEngineer]

I set mine so that there is a trickle coming from the secondary drain. If the line is under the water an inch or two, you shouldn't get any escaping bubbles from that.

 

[Mandelstam]

Can you fit an elbow on the main drain so the intake is below the actual drain level? That should make it draw less air.

 

[Salt1972]

Can you fit an elbow on the main drain so the intake is below the actual drain level? That should make it draw less air.

I tried that. It starts a siphon and just lowers the level until it starts drawing air again. I did restrict the output of the primary (like a suggested valve would do) and it does seem to fix the problem. I'll pick up a gate valve and put it on the primary overflow tomorrow. Thanks for the suggestions / help.

 

[Salt1972]

It's actually not a terribly delicate adjustment. What you have there is essentially a herbie overflow minus the valve on the primary drain.

And just like that... there were no more bubbles. Thanks Engineer! I'm surprised at how accurately the valve allows the level in the refugium to be set. I hope it's consistent and doesn't require daily adjustment. Either way, thank you for the suggestion.

Now... to add a light and some chaeto.

 

[TheEngineer]

You are quite welcome Happy to hear it worked for you!