Micro Bubbles and Closed Loop

[eugene22_73]

Having a problem with micro bubbles and would like any suggestions. Last weekend I installed an undrilled closed loop/manifold like on www.melevsreef.com for my 75 gallon tank. Using a Velocity T4 as a return to 3 teed outlets, one on each end and in the middle (apprx 400gph per outlet). Using 1� return from the pump to ¾� pvc manifold, reducing to ½� teed outlet/loc-line. The intake to the pump is 1� pvc. It works great and is quiet. Only problem is the mico bubbles coming from the return/teed outlets. I can see that air is blowing with water. I’m at my end of knowledge to figure this out. Trying to search forums, but last few nights a sever overload so the function doesn’t work. Any suggestions?

[Sugar Magnolia]

It'll take a few days for the pump to break in and for the pipes to slime up. The microbubbles should gradually disappear for you.

[Bax]

If the bubbles don't go away in a couple of days or so look for small leaks on the suction side of the the loop out side of the water.

[Anthony Calfo]

exactly as Bax and Sugar Magnolia have stated or implied... the aspiration of bubbles from pinhole leaks in glue/joints/fittings (especially simple barbed fittings and/ort hose clamps).

Do rule out these common issues first by checking joints, starting with any unglued unions.

Then... for the glued joints, you can systematically smear a little bit of petroleum jelly on each joint then wait a few minutes to see if the bubbles stop. We are obviously trying to rule out leaky joints one by one here. (Do wipe off the jelly when you are done )). Check the suction as well as output sides of the external plumbing... either can aspirate air and make bubbles.

Then there is the possibility of the pump housing itself leaking air. Its uncommon but no fun to diagnose or fix.

[WarEagleNR88]

I posted on another thread--thanks for the response fish_taste_good, but am still having some of the same troubles as Eugene. If my CL pump makes a LOT of noise (high dBs, sounds like it has rocks thrown into the intake), is it most definitely an air leak on the intake side?

It makes me think the intake housing may be cracked/have small leak/etc because every joint is glued tight (lots of glue on purpose, had to whipe off excess) and it was working fine while in a sump. I did the hearing test with a piece of PVC on all joints and still nothing. But as I get closer to the pump, it's hard to hear anything but the crash of air bubbles. Oh and there are lots of microbubbles in the display coming out of the CL.

And is there any danger in putting petro jelly in to check for leaks? Does that do anything to the system or will the skimmer get it--or should get it I should say?

Any help Anthony?

[Anthony Calfo]

the jelly is mostly wholly harmless (can degrade some seals... but no harm in water or to PVC joints)

[Jpizzle]

WarEagleNR88

sounds like your experienced cavitation.

do a search and you should come up with info.

The best solution would be to increase the pipe diameter of the input side of the pump.

[WarEagleNR88]

Jpizzle, all pipe upstream and downstream of pump is 1.5"ID. CL pump is a Mag 18 and has 3/4" FPT intake and 3/4" outlet. I could probably do 2"ID on the inlet, but I don't think pipe size is the problem there.

Anthony, I'll try the petro jelly and see if I can find a leak.

[WarEagleNR88]

Thinking about it though, it may be cavitation. But for why all of sudden it would happen, I'm not sure. It seems as though danner would know what's the right size on their pump to prevent cavitation. That would have been figured out in design and test phase. I can't *make* the inlet any larger. And would I be the only one to ever experience this? I seriously doubt it.

I'll check the whole situation out tomorrow and hopefully come back with an answer or observation.

[janakaybravo]

Hi. I started my tank 3 months ago and have lots of micro bubbles. I didn't know what to do, called LFS and they said to get the skimmer return away from where the pump sucked up the water. The skimmer return was creating bubbles and the pump was sucking them up and putting them into the tank. Does that make sense? I don't know nothing about plumbing. Anyway, it's improved quite a bit since I moved the skimmer return as far away from the pump as possible.

[Anthony Calfo]

Not to pass the buck, my friend... but I see that you are fairly new to RC. And... in the spirit of truly helping you to help yourself and learn what a fabulous resource the RC archives are, let me encourage you to do some keyword searches with the convenient search tool for such topics as "microbubbles"

After you've had a chance to see some of the fabulous input and solutions for this in other threads... do write back then if needed.

[WarEagleNR88]

Anthony, I did a lot of checking on my CL this afternoon since I had a little bit of time off and I do not know where the air leak would be or if it is cavitation.

First, I did a sound check. I put a foam ear plug in one ear and the end of a 1/4" vinyl tubing in the other and tried to listen at each intake leg joint (3 elbows, 2 street tees, 1.5" to 3/4" reducer, union, male coupling, impeller housing). I did this on all "power" settings of the ball valve on the outlet (I only use 1 ball valve). Nothing. No air leaks that I could tell (and this is with the room as quiet as possible) and no water leaking out with the valve turned off.

Next I tried rubbing vaseline on all of the joints. Nothing. No decrease in bubbles, no real detection in a leak.

Then I pulled apart the Mag 18, cleaned what little funk it had inside of it, checked for any visible cracks (none), and put it back together carefully in order 1-4-2-5-3-6 (CCW screw rotate for drop, slowly CW until as tight as 3 fingers on the screwdriver could get the screws) like you're supposed to do on a Magdrive. Back together, still has noise.

I'd like to mention something interesting, well actually a couple of things. Ever so often while it's running, there'll be a change in tone of the "grinding" of the air bubbles almost as though it's going to clear up and go to the gentle hum of a mag pump. But it returns back to the bubble grinding. Also, with the ball valve almost closed (about 20-25% open), with my vinyl tube I can still hear the impeller smacking bubbles. This is the key thing that makes me think it's not cavitation.

I think my next step will be to carefully replace the impeller housing (gotta by a replacement) and see how it goes from there. Any insight?

[Anthony Calfo]

not hearing any noise with a restriction of output does not exclude cavitation, mate. My Hammerhead is cavitating and it also does not get much better when I restrict the outflow. My problem is that I am drawing water from too far away (3 feet) and through two elbows. So even though the pump is flooded properly... the plumbing is a bit too far away (feed pipe size is large enough though in my case)

[WarEagleNR88]

Ouch, i didn't know that. How do you fix this then? Or is it not fixable?

My intake is about 3' away from the pump and seems as though it would be adequately fed.

Grrrrr this is frustrating.

[Anthony Calfo]

WarEagleNR88... our pumps are too far away

The best installation is a large inlet (2" in my case) tapped directly into the tank/sump with little or no run of pipe/elbows, etc.

If you can replumb this, please do so (and increase intake pipe size if needed)