Micro-bubbles in display tank

[1320wrx]

I started to notice a lot of tiny bubbles being blown into my display tank from the returns. I have lockline on my returns that are exposed out of the water. Is there any way there could be a small gap in the pieces of lockline that is creating a venturi, Has anyone ever used lockline where it is exposed out of the water and didn't get mirco-bubbles. There is salt creep on my lockline where each section fits together so it is obvious that the seal is not perfect.

I don't see any kind of bubbles being sucked in by the pump and i don't have any bubbles going through my phosphate reacter. The only thing I can think of is the lockline.

Anyone else have any ideas?

Steve

 

[JohnS_323]

I have places with exposed locline and don't have any problem with micro bubbles. I also don't have any salt creep on them, that I've noticed.

Are the bubbles really small? If so, it would most likely be some pinhole leak before the pump and the pump is cutting them up. It could also be caused by cavitation if the flow of your pump is somehow being restricted. If they're larger bubbles, they're probably from some leak after the pump.

Nothing really earth shattering there but I hope it helps!

 

[DaveK]

These kind of problems can be difficult to track down.

First, look at the water in your sump, and make sure your not getting bubbles from a skimmer or other device there, or from the water coming into the sump. If that's the case, the return pump will simply "recycle" them to the main display tank for you.

Assuming that you are using a sump, and that the water there is clear of micro bubbles, the usual cause is a leak somewhere on the intake side of the pump, or the pump itself. Things like lockline can be a problem if it's on the intake side of the pump. It only tahes one very small leak to cause a problem. A leak on the output side will usually just give you salt creep.

 

[1320wrx]

Are the bubbles really small? If so, it would most likely be some pinhole leak before the pump and the pump is cutting them up. It could also be caused by cavitation if the flow of your pump is somehow being restricted. If they're larger bubbles, they're probably from some leak after the pump.

Yes the bubbles are very small, like the size of bubbles inside a skimmer

The pump I am using is a Velocity T4, it has a 1" hose barb for the intake and return. I then reduce the PVC to 3/4 for all my return plumbing and my manifold, Is this enough restriction to be causing cavitation. Im not really sure what cavitation is???

Is there any way I can run a bead of silicone around each joint to try to narrow the leak down. The tank has been set up for two weeks and the problem just started 2 nights ago.

 

[chessmanmark]

How is your sump set up? Do you have it running in one direction or is the return pump in the middle?

One small trick can be putting some LR below your overflow pipe. This will break up many of the larger bubbles. Then you can buy sheets of filter media and place them in your baffle to break up remaining bubbles coming through the baffles, however those mini bubbles could be a small leak somewhere after the return. Are all your return pipes glued? How many returns do you have and are the micro bubbles coming out each one?

 

[1320wrx]

How is your sump set up? Do you have it running in one direction or is the return pump in the middle?

One small trick can be putting some LR below your overflow pipe. This will break up many of the larger bubbles. Then you can buy sheets of filter media and place them in your baffle to break up remaining bubbles coming through the baffles, however those mini bubbles could be a small leak somewhere after the return. Are all your return pipes glued? How many returns do you have and are the micro bubbles coming out each one?

Here is my build thread, you can see how my sump is set up.
http://www.njreefers.org/joomla/index.php?option=com_smf&Itemid=26&topic=12319.0

I can't see any micro bubbles being sucked into the pump, and all my plumbing is glued an teflon tape is used on all threaded joints. The first thing I want to do is eliminate the lock line being exposed out of the water. There is salt-creep on them, that is tellin my they arn't water tight.

Is there any way the pump can be drawing air into it through the impeller housing

 

[JohnS_323]

Are the bubbles really small? If so, it would most likely be some pinhole leak before the pump and the pump is cutting them up. It could also be caused by cavitation if the flow of your pump is somehow being restricted. If they're larger bubbles, they're probably from some leak after the pump.

Yes the bubbles are very small, like the size of bubbles inside a skimmer

The pump I am using is a Velocity T4, it has a 1" hose barb for the intake and return. I then reduce the PVC to 3/4 for all my return plumbing and my manifold, Is this enough restriction to be causing cavitation. Im not really sure what cavitation is???

Is there any way I can run a bead of silicone around each joint to try to narrow the leak down. The tank has been set up for two weeks and the problem just started 2 nights ago.

I've always heard that a pump starved for water will cause cavitation issues but didn't really understand why so I did a little research and found THIS link. I think the Internal Recirculation is caused by restrictions. One rule of thumb I always heard was to step up your pipe going into and coming out of the pump. In your case, you would step up to 1 1/4" pipe at the pump and carry that size as far as you can, stepping down to 3/4" as close to the tank as possible.

I can't say one way or another that cavitation is the issue but I thought I pass this info along.

Good luck!

 

[DaveK]

In looking at your sump build, I see two possible problems.

First, I would want a much larger return chamber for the pump. You may be sucking air because this final chamber gets drained too low. You may need to remove the "refugium" section and build an external refugium.

Second, get rid of the hose barbs, hose clamps and flexible PVC tubing on the pump intake side. This can be a major source of problems. I recommend you replace it with a true union ball valve, and cemented PVC pipe. Flexible PVC pipe, also know as SPA Flex, can be used.

I also highle recommend a second true union ball valve on the output side of the pump. This alloes the pump to be removed for service.

While the hose barbs and flexable PVC tubing and lockline, on the output side, would not be my first chouce, I doubt if they are causing your micro bubble problem.

 

[1320wrx]

Are the bubbles really small? If so, it would most likely be some pinhole leak before the pump and the pump is cutting them up. It could also be caused by cavitation if the flow of your pump is somehow being restricted. If they're larger bubbles, they're probably from some leak after the pump.

Yes the bubbles are very small, like the size of bubbles inside a skimmer

The pump I am using is a Velocity T4, it has a 1" hose barb for the intake and return. I then reduce the PVC to 3/4 for all my return plumbing and my manifold, Is this enough restriction to be causing cavitation. Im not really sure what cavitation is???

Is there any way I can run a bead of silicone around each joint to try to narrow the leak down. The tank has been set up for two weeks and the problem just started 2 nights ago.

I've always heard that a pump starved for water will cause cavitation issues but didn't really understand why so I did a little research and found THIS link. I think the Internal Recirculation is caused by restrictions. One rule of thumb I always heard was to step up your pipe going into and coming out of the pump. In your case, you would step up to 1 1/4" pipe at the pump and carry that size as far as you can, stepping down to 3/4" as close to the tank as possible.

I can't say one way or another that cavitation is the issue but I thought I pass this info along.

Good luck!

Well, I was hoping that this want the case but I guess I'll re-plumb the whole tank. You live, you learn I guess.

 

[Hawkeye]

follow up on dave's comments...the return section does look low in that last pic.

How are you doing top-offs? If you set a auto-top-off so that the return never runs that low - then maybe that will solve the microbubble issue?

I don't know why you'd have saltspray on the locline - that stuff was almost impossible for me to hammer together - I can't imagine it leaking water....you sure it's not coming up from the display somehow?

 

[chessmanmark]

I'm surprised you don't see any problems prior to emptying the sump. At a quick glance I would think you need another baffle on the right side but you say you don't see bubbles there. I agree with Dave about the last chamber as well. You don't want that running so low. IME you see some turbulence in the chamber with your return pump when you get bubbles in your display.

 

[1320wrx]

In my last chamber of the sump i cut a piece of foam that the bubbles get caught in. I will post some new pictures of the sump with the foam installed.

I am probably going to re-plumb the whole tank, the pump is getting pretty warm i think i do need bigger plumbing

 

[concept3]

In my last chamber of the sump i cut a piece of foam that the bubbles get caught in. I will post some new pictures of the sump with the foam installed.

I am probably going to re-plumb the whole tank, the pump is getting pretty warm i think i do need bigger plumbing

Steve, before you re-plumb the tank, try using a smaller pump if you have one, if not, see if you can redirect the excess pressure to feed or power a skimmer. My pump is an iwaki 20, only at 420 gph and that is enough for sump circulation

 

[chessmanmark]

I was following along with this thread partly because I was getting micro bubbles too. I recently rebuilt my tank and while the configuration of my sump is the same I moved the skimmer, eliminated the refugium, changed my return pump, and added another return. Each day I played with the ball valves and would get rid of the micro bubbles only to get them the next day as the water level in my sump changed. I tried filter media in the last baffles but my carbon and phosban reactors dumped into the return section causing some bubbles. Today I took a piece of plexiglass and leaned it out from the last baffle. It's not permanent but resting back on the return pump. This was enough to stop the micro bubbles and the splash from the two reactors. It acts like another bubble trap. What a relief to see a nice clear display without redoing to plumbing.

Keep playing around you may figure out a quick fix without a lot of labor.