possible microbubble source

[astroboy]

Hello all,

 

I'd been having trouble with a nuisance-level amount of microbubbles for as long as I've had my set up. Their source in the main tank is the return from the sump (not surprisingly). I sealed all connections to make sure that wasn't the problem, no luck.

 

Finally, just as an experiment, I directed the outflow from my in sump skimmer (RS-80) into a cylindrical plastic container with the edge half an inch above the water level in the sump. The output from the RS-80 is supposed to be above the water level in the sump: I have my output pipe cut off at an angle so that part of the opening is above the water level, thereby avoiding a sort of back pressure in the output which make the skimmer alot more finicky to adjust. (Due to something like surface tension, the output water sticks to the end of the pipe that is below the sump water level, reducing the noise a bit).

 

So, the basic setup is that the output empties into the plastic container, where it overflows into the sump. The output pipe is cut an at angle, so there's 'open air' at the end, even though the water level in the container is a bit higher than the sump.

 

The microbubbles went away.

 

My guess is that they tend to disperse in the plastic container, so when the water reaches the sump (and return pump) it has a greatly reduced number of bubbles, or perhaps perhaps it's just quite so aerated, thereby avoiding cavitation bubbles in the pump return water to the main tank.

 

Anyway, for my particular set up it worked great, your mileage may vary.... It's a simple thing to try, anyway.

Edited October 5, 2009 by astroboy

[steveoutlaw]

Can you post a pic of this setup? I've got an RS-80 that I'm having a micro bubble issue with as well.

 

thanks.

[astroboy]

Can you post a pic of this setup? I've got an RS-80 that I'm having a micro bubble issue with as well.

 

thanks.

 

Well, there's so much junk in my sump a picture might be worth one word, instead of a thousand. Let me explain more clearly.

 

The RS 80 has an output pipe, which you're supposed to cut to be above the water line of the sump. As I understand it, from the euroreef website, if the opening of the output pipe is below the level of the sump water a back pressure builds up, since the outgoing bubbles/water have to force they way to the surface making adjusting the level of the foam within the skimmer alot more finicky.

 

If you cut the output pipe so that its an inch above the sump water level, you get noise from dripping. I have four small children, I don't need any more noise. So I cut the end of the output pipe at about 45 degrees, so that one edge is below the level of the sump,and one edge is a couple inches higher. The water tends to run down the "deep" end into the sump water with alot less noise. Conversely, there's a large part of the opening exposed to the air above the sump: hence no back pressure.

 

Problem is, still alot of microbubbles, enough to be a pain. I actually did two things, only the first of which I mentioned in the earlier post, since I think the second is small change.

 

1: I put a plastic cylindrical container (ie, tupperware or a truncated peanut butter jar) so that the output tube emptied into it, rather that directly into the sump. (As things stand now, is sitting on to of the pump, with no apparent ill effects). The top of the plastic PB jar is around half an inch above the level of the sump water. It seems to be that all the bubbles from the output pipe, which are mostly from the foam inside the skimmer,"pop" in the PB jar. By the time the water has overflowed into the sump, all the "carbonation" if you will, has worked its way out. Sounds too good to be true, but by gosh it seems to work.

 

2: I was getting alot of racket from the two Maxi jet 1200s that returned the water from the sump to the main tank, and also pumped water thru the GFO and activated carbon BRK reactors I have (which I highly recommend). I took some of that black/gray plastic foam used for packing computer stuff and enclosed both maxi jets in it using cable ties. The reduction in noise was *amazing*. (Not sure why, the pumps and impellors were both brand new with hardly any vibration, but oh well...)

 

In addition, for the sump return pump I superglued a quarter inch thick slice of foam rubber to the end of the covering foam, not directly to the pump intake. The basic idea is that the maxi jet was covered in foam rubber: nothing airtight by any means, but enough so that 95%of it was covered. That was mainly to cut down on vibration noise being transferred to the sump, that is, no hard plastic was in contact with the sump walls. Of course, this 95 % coverage also covered up the pump intake (sort of), but let me emphasize: there was a half inch gap between the intake and the foam rubble. There were enough openings for water to be sucked in by the pump: I was just trying to cushion the pump from the sump sides and bottom.

 

I did experiment a bit and here's what I think:

 

1) the flow from the output pipe into the container eliminates 90% of the bubbles, or at least has the effect that the water isn't so saturated with air that bubbles form via cavitation in the turn Maxi jet pump.

 

2) The 95% coverage from the foam rubble definitely doesn't significantly reduce the water going into the maxi jet. However the foam probably does collect a few more bubbles, but I'm guessing here, really. I haven't tried taking the foam off to see what will happen, although the bubbles were greatly reduced by the PB jar, prior to me adding the foam.

 

 

 

So, the bottom line is, trim the output from the RS-80 at a diagonal so part of it is open to air, second, have it empty into a small reservoir again, so that part of the diagonal is open to air, and see what happens. The resivoir should be an inch, perhaps, above the sump water level.

 

As a second step, cover all the pumps in the sump with foam rubber, leaving some "breathing space". It will cut down on vribration noise anyway. Does it help help with bubbles, yeah probably a little bit, and cable ties and foam rubble are cheap so its worth a try.

 

Any questions, send me a email: mfquigley@wisc.edu or call at 703 876 6296. It would be nice to find a cheap way to get rid of this mcrobubble problem.

 

I'd be really interested to see if anything you tried worked...

 

 

Mark

Edited October 6, 2009 by astroboy

[Amuze]

I wouldn't have cut the pipe. I ran a RS for a couple of years and never had an issue with the pipe being fully submerged. Never cut it. Never had issues with it being finicky other than what usually happens with any skimmer if you top off a lot of fresh water. No micro bubbles and no noise either. Mine was sitting in 6" of water in the sump. You can try putting a filter sock on the end of it.