eliminating bubbles from CPR bakpak return

[cyannotater]

Does anyone have advice on eliminating bubbles (and thus the noise) from entering the water flow on the return on a CPR bakpak skimmer (or skimmer/refugium in this case). Basically the unit has an approx 1" bulkhead to which and elbow is mounted for the return into the tank. Air is entering along with the return water which drops a few inches into the tank below the water surface where another elbow directs flow horizontally in tank.

Any good ideas?

 

[Behrmon]

How much of the return is submersed? I used to just raise the water level to have 3/4's of it submersed and that helped.

 

[PenMan]

I will not cut down on the noise, but if you are getting bubbles back into the tank, you need to increase the air. This seems backwards, but it cuts down the water flow and give the bubbles a time to leave the water. The elbow return should be below the water level of the return.

 

[conrad]

Sounds like this is an AquaFuge/PS, right? (You said skimmer/refugium.) It's hard for me to imagine bubbles injected by the venturi making it all the way through the fuge to the return.

It could be that the bulkhead on your return is loose and you're getting air sucked in there. Which style of return do you have, the old style with an inverted U-tube going down almost to the bottom of the return chamber, or the new style with an inverted L-tube (nothing but the bulkhead hardware in the return chamber)? An old style with a loose bulkhead can inject bubbles into the display.

PenMan is absolutely right about air into the venturi vs flow through the fuge, so that's another thing to play with. You'll get better skimming with more air too.

But let us know which style return you have. The old inverted U-tube style seems much more prone to bubbles and noise in my experience.

 

[reefsmurf]

CPR sells a prefilter surface skimmer bubble trap. I am selling it with my CPR but now I might hold on to it instead due to lack of interest

 

[conrad]

CPR sells a prefilter surface skimmer bubble trap.

I think this is an AquaFuge/PS, so I don't think this would work here. The return is spaced much further from the intake when the protein skimmer has a refugium integrated into it. He should certainly be able to tune things so that he has no bubbles returning to the display without using a bubble trap.

For surface skimming, simply cut a slot in the venturi intake airline at the water level range. Works great!

 

[smithcreek]

I used to just hold a couple fingers in front of the bulkhead until the water level rose to the top of the bulkhead. Most of the time when I took my fingers away the noise and bubbles stopped. You just have to do it every time you stop the skimmer and restart..

 

[cyannotater]

new style

Thanks for the input so far. You're right Conrad its the aquafuge/PS making the bubble trap they sell not an option. The bubbles aren't tiny bubbles injected by the venturi making it all the way through. The return is the "new" style which is just an L-tube (nothing but the bulkhead hardware in the return chamber). This tube is about 4" long (goes about 0.5-1" below the water level in the tank) and has another elbow on the tank end directing flow parallel to the water surface. The air bubbles are large and introduced by the turbulent flow out of the refugium down the 4" drop into the aquarium.

Smithcreek - I've tried many variations on the "hold your fingers over the bulkhead" none of which work. Once the water level goes above bulkhead return I get a flushing of water as it quickly siphons out till the water level is once again at a point where air is being sucked in along with the water. Maybe I should check out the reverse durso I've heard people use for quieting sumps - seems like what I need. I'd like to solve the problem with a minimun of tubing/hardware in the tank though.

 

[conrad]

Have you played with the depth of the return tube in the display? I believe it is a telescoping fitting (it is on at least one of the old and new styles), so you can play with the length. Perhaps extending it a bit further may help. Also, if I recall it works poorly at its shortest setting, with the tube jammed all the way up, since it blocks the flow a bit. Apologies if it only telescopes on the old style and this is irrelevant to the new style. I had lots of trouble with my old one, but that was because the bulkhead was loose and I didn't know that the display side of the return telescoped. I realized these things while swapping in my new one and only had to fiddle with it a bit before it was working great -- and has continued working great since.