Fighting air in return line. Why?

[Chrysemys]

I felt I needed to add a refugium onto my system which was operating with just a canister filter. I had a 20 long laying around, so I drilled it installed 3/4” bulkhead and plumbed canister filter outflow to opposite side of the tank from the bulkhead. Set the bottom of the bulk head level with the display tank and plumbed the out flow back to the display. I hope the pictures explain it well enough.

At first canister output was too much for 3/4 bulkhead to handle. Then I plumbed in a tee to spilt and control flow from cannister to refugium and display tank.

That worked, but over time air would build in my plumbing and restrict flow back to display from the refugium. I then installed a tee instead of an elbow to allow air to leave the elbow.

This helped but about once a week I still get an air restriction. It backs up flow from the refugium until I think it is about to overflow than the pressure blows the bubble through the line.

You may ask, “why the dip in the return line
rather than just a straight pipe back to display tank?” I wanted to hide the hole in the wall behind the tank.

It works but I would like it to work better. Any suggestions other than scrap the whole idea and just do a regular sump?

 

[Flippers4pups]

For simplicity sake, I would rather have sump.

Using the canister to feed the refugium, that feeds the display, then has water pulled back to the canister sound ls like a problem to keep dialed in. Which you are having.

 

[JoshH]

In lieu of a sump You could 45 the pipe between the two heading upwards, this will naturally force air up to your second air relief and prevent build up on the horizontal section

 

[KrisReef]

Can you raise the refugium?

 

[theMeat]

For simplicity sake, I would rather have sump.

Using the canister to feed the refugium, that feeds the display, then has water pulled back to the canister sound ls like a problem to keep dialed in. Which you are having.

Yes, agreed

Go back to first pic/design. Where canister goes to fuge, then to tank. If you can’t run the overflow straight from fuge to display, then put the tee with rise for air on top of final rise instead of elbow. The tee will work better there, than where you have it. Another words move the tee one fitting back towards fuge

 

[WVNed]

How does air get in it? I would install a 90 degree bend turned down in the bulkhead and extend it down a few inches so it cant swallow air. Remove the first air break. Change the second air break to a tee in the vertical section behind the tank by swapping the elbow and the tee above the tank.

That would be a flood waiting to happen though. you would need a hole to break the siphon in the fuge

 

[Chrysemys]

The tee will work better there, than where you have it. Another words move the tee one fitting back towards fuge

That makes sense. I should have thought of that. Thanks for the idea. I will give it a try.

I leave just enough room, about 1/2”, in my display to make room for any siphon from fuge, so I don’t have a worry there. Power outages have tested that for me a few times.