tiny bubbles from return line

i just set up my 210 gal tank the other week and i cant seem to clear up the return water, i keep getting these tiny little bubbles shooting out of the pvc. Any suggestions would be great, these bubbles are driving me nuts
 

fretfreak13

Active Member
Mine only does this after my tank water evaporates a bit and part of the return pump is exposed to air. Make sure this isn't the case, and if it is, add some top off RO water. =)
 

reefkprz

Active Member
there are a couple possibilities. I'll give you a short list of possibilities, you can eliminate them.

cavitation, the pump itself is faulty causing cavitation introducing bubbles to the water, this will also wear out the pump at an extremely fast rate
air pocket in plumbing, there could a small pocket of air stuck in your plumbing and the water flow is snagging bits of it, this should clear up on its own.
if you have a sumberged pump, the return pump could be too close to the water surface so its sucking air (some pumps need to be submerged a minimum distance to keep from creating a whirlpool and sucking air) generally the larger the pump the deeper it needs to be to prevent this. generally a few inches is plenty.
if you have an external pump micro bubbles can indicate a leak on the pickup side causing air to get sucked into the plumbing, usually at a joint or elbow. I would run a bead of pvc cement around all my joints, allow to dry then re-try.
 
Originally Posted by reefkprZ
http:///forum/post/3161186
there are a couple possibilities. I'll give you a short list of possibilities, you can eliminate them.

cavitation, the pump itself is faulty causing cavitation introducing bubbles to the water, this will also wear out the pump at an extremely fast rate
air pocket in plumbing, there could a small pocket of air stuck in your plumbing and the water flow is snagging bits of it, this should clear up on its own.
if you have a sumberged pump, the return pump could be too close to the water surface so its sucking air (some pumps need to be submerged a minimum distance to keep from creating a whirlpool and sucking air) generally the larger the pump the deeper it needs to be to prevent this. generally a few inches is plenty.
if you have an external pump micro bubbles can indicate a leak on the pickup side causing air to get sucked into the plumbing, usually at a joint or elbow. I would run a bead of pvc cement around all my joints, allow to dry then re-try.
i have a dolphin 2800 external pump, the pump is plumed about 12 inches under the water line and all pipes are glued together, i did find a few small leaks but used a bead of silicone all the way around the edge of the leak. When you say a leak on the pickup, what do you mean by that. I will try to post a pic but for some reason i cant get it to work on this site. You also think if i turn off the pump and let the water flow back down then restart, that it will clear any air out from the elbows like your talking about. Im getting so frustrated with this issue, its driving me nuts, my tank looks like cloudy all the time.
 

reefkprz

Active Member
you have an inlet side and an outlet side on your pump. the plumbing that picks up the water and brings it to the pump is where the leak allowing air into the system will be. you wont see water leaking out on that side because the suction of the pump will suck air in instead. if you found leaks on the oulet side it will leak water, like you said happened. I would shut of your pump for a day and reglue all your seams on the pickup side. dont use silicone on PVC its unreliable over the long haul, use PVC glue.
 

bang guy

Moderator
The test for cavitation is to restrict the waterflow on the output side. If the bubbles go away when you reduce the flow 10% or so then it's a good chance it's just cavitation.
 
Originally Posted by Bang Guy
http:///forum/post/3169967
The test for cavitation is to restrict the waterflow on the output side. If the bubbles go away when you reduce the flow 10% or so then it's a good chance it's just cavitation.
ok, so i just read a link to cavitation and i am completly lost, can you put it in lamens term for me. If I could understand whats going on, I can visualize the solution.
 

reefkprz

Active Member
Suction Cavitation occurs when the pump suction is under a low pressure/high vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitation condition has chunks of material removed from its face causing premature failure of the pump.
 
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