micro bubbles from closed loop system

[moeandicy]

Just completed and installed a closed loop system on my non-drilled 72 gallon bowfront. It's being driven by a little giant 3mdx-sc pump and is running through a scwd and output through 3/4 in cpvd and 3/4 in lockline fittings. Everything appears to be working correctly and there aren't any leaks that I can see. Unfortunately I'm getting a large amount of micro bubbles. Anybody have any clues what might be causing them?

 

[dwall174]

Do you have a 90 degree fitting close to the intake of the pump? If so it could be a source of Pump Cavitation

 

[moeandicy]

There is a 90 degree fitting (the first one from the intake side) about 8 inches or so from the pump.

 

[wrightme43]

8" is probley enough not to be the cause of the cavitation, in my opinion. Is it possibley sucking air anywhere? Is it a used pump? Is there anything on the blades of the impeller. including flashing from manufacture. Sometimes it goes away with a few weeks of run time. The rough edges get covered with bacterial slime and the bubbles go away. You could put two 45 fittings or use a P trap bend to sweep the water instead of a 90 but I doubt if it is that far away it is the cause of your problem.

 

[moeandicy]

The pump is new. I can try the 45s later today. That should be an easy mod. I don't think it's sucking air anywhere. I was afraid of this from the beginning so I made sure all of my connections were tight. What is a P trap?

 

[dwall174]

I use to work with hydraulics several years ago & the rule of thumb was to have a straight section of pipe 10 x the inlets dia. So for a ¾” pipe inlet you would need 7.5” Of course hydraulic fluid is a lot different than saltwater so I’m just using that as a comparison, But I think 8” should be fine! I agree with Wrightme43 that it’s probably sucking air in from some where? All it needs is a tiny pin hole or a fitting not sealed good to cause all kinds of bubbles. Chances are that the source of the air is on the inlet side so if you can get at the fittings you could try adding a thin bead of silicone at the connections & see if that helps!

 

[wrightme43]

I agree. I went thru hydrodynamics classes in the navy ( I was on subs as a sonarman) we were responsible for sound silencing. Any cavitation is a noise generator so we had to know what caused it, and how to make it stop. And what that noise was we were hearing on another sub we were tracking.
A p trap is the thing under your sink. It comes in pvc. You can get them in slip fitting and they have a sweeping bend that doesnt restrict flow. I just used 45 fittings on mine. HTH Steve

 

[moeandicy]

Thanks everyone. I'll try the 45s later today and let you know what happens.

 

[Marc]

It could be sucking in air from anti-siphon holes, or any plumbing that is unglued and not submerged. It could also be where the tubing is connected at the SCWD. Did you put hose clamps on those spots? If so, did you clamp at the smooth section after the nipple, or right at the end of the nipple?

 

[moeandicy]

Yes I put clamps on the scwd where it connects to the hoses and I put them on the flat part of the scwd. I used pretty much the exact same design as on Melev's Reef's site. Planning on going back and double checking all the fittings again later today.

 

[Marc]

What type of tubing did you use? Did you heat it up to soften the material some? That tends to help, incase the problem is at the SCWD.

 

[moeandicy]

I just used some 3/4 tubing from Lowe's. Didn't think to soften it with anything since I assumed if I had problems it would be from the pvc fittings not the hose. Maybe I was wrong.

 

[moeandicy]

Here's another question...besides being unsightly...what problems can these bubbles cause?

 

[Marc]

Keep in mind that brand new plumbing will generate microbubbles, which clear up within 2 weeks as the inner walls slime over. Are we talking about bubble soup or just some annoying bubbles?

Heating tubing can be done easily. Put it in the oven at 200F for 5 minutes, and it is soft and pliable. I just heated up 1.5" SpaFlex for my skimmer modification, which worked out great.

 

[moeandicy]

Ok...I replace the 90 with two 45's. It helped marginally but there are still a mess of bubbles. Not as annoying as before. I think I will wait a week or two to see if they go away as suggested above. Thanks for all the help.

 

[mojoreef]

Is the locline completely submerged??

Mike

 

[moeandicy]

No it's not...guess I'm going back to lowe's today. LOL Man I love this site.

 

[mojoreef]

their you go

 

[wrightme43]

Uhhhhhhhhhh Duhhhhhhhhhh. Good Save Mike. LOL Why couldnt I think of that. LOL Steve

 

[Marc]

Great detective work. I did ask about all joints being submerged that were not glued, but didn't notice the locline mentioned.