Help! Small bubbles from return pipe into tank

[ken6217]

I was hoping that someone may have an idea what is causing the small bubbles coming out of my return pipe into my tank. I have a 90 gallon AGA mega flow tank which has the internal skimmer box. It is a new tank. I put saltwater in it 8 days ago. 6 days ago I added about 120 lbs of live rock. I have a 48” MTC Beckett style skimmer coming off the other side of my sump which has two baffles. When I look closely at the return to tank side of the sump, I really don’t see any bubbles to speak of so I do not think that this is the reason.

The water flow from my sump to my tank is as follows:

¾” pvc flex tubing into ¾” union >>> Blueline 40 pump >>> 3/4” flex tubing >>> bushing to increase to 1”>>> 1” ball valve >>> 1” union >>>1” ball valve >>> Bushing to decrease to ¾” >>> ¾” pvc >>> two 90 degree ell’s into my chiller >>> two 90 degree ell’s from my chiller >>> ¾” flex pvc into the bottom of the tank for the return.

The other problem (and maybe related) is that when I put my hand in front of the return line into the tank, I hardly feel any flow. The Blue line pump is rated at 790 gph @ 5’ head. I used the head loss calculator and I should have at least 560 gph. I am not sure what that feels like against my hand, but it has to be more than what it seems.

I appreciate at any idea someone may have.

Thanks,
Ken

[cilyjr]

they are micro bubbles in the sump if you build a bubbletrap in the sump near the return pump that will trap them...here is a section taking from Melevsreef.com ( http://www.melevsreef.com/allmysumps.html )
A bubble trap is a narrow section within the sump that is made up of three baffles. The center one is higher than the two outer ones. The bubble trap should be located after the area that contains the most bubbles. Normally, that would be where the water enters the sump and your protein skimmer is located. Microbubbles abound in this zone, so the bubble trap would be set up next, to prevent these from continuing through to the refugium and/or return section. If you have a refugium next, you'll need one more baffle between the refugium and the return section. All four baffles should be the same height in this setup.

[cilyjr]

as far as flow you would have to get a flow meter to check i guess

[ken6217]

I don't think it is micro bubbles. I do have baffles in the sump. When I look at the non-skimmer side of the sump, I do not see any bubbles. I guess when Iget home tonight I can shut off the skimmer and see if the bubbles stop, but I don't think that is the problem.
Ken

[cilyjr]

i was getting bubbles in the display and i didn't see any in sump until i put my baffles. maybe the pump is sucking air somehow. like the return line is cracked and its reducing flow because some water is returning to the sump and the air is getting sucked in and up. but i dunno just an idea of something to look for. disconnect and run the return pump in a bathtub. see if you are getting good flow. good luck

[yakfishin]

Bubbles are hard to see in the sump when they get fewer in number. To really see if any are making it to your return pump, try turning off all lights in the aquarium and room and then shine a flashlight through the side of your sump while looking from the top, if any are making it to the pumps return you should be able to see them that way. If you don't see any bubbles using that method, you may have a pinhole leak at a joint that is allowing air to come into the return line.

[ken6217]

Thanks. I will check both tonight to see if it is a pinhole or if it is bubbles in the sump. If I don't see bubbles in the sump, then I will re-do the plumbing as I had to replace my chiller and I am getting my new skimmer. I will be 50% there anyway.
Ken

[yakfishin]

Some people check there return lines before redoing them by smearing vaseline or silicone around all the pipe joints to see if the bubbles disappear. I personally don't think vaseline, which is a product from pertroleum, is good for PVC. This would seem to take just as long as redoing the lines, but I have never done it. I think if you look into your sump from above, using the flashlight shined from the side, you may see some bubbles that you never new existed getting to your return pump. Bubbles are pain to figure out sometimes, good luck and let us know how you do.

[fingersdlp]

Could be cavitation. If the flow into the return pump is restricted it can cause this. Not sure if the plumbing on the output side can contribute to cavitation or not.

B.