I don't get it?

[flameangel9]

How does a powerhead thats fully submerged spit out tiny bubbles that fill the tank.
Where's the air come from? The power head did this early on when I first set the tank up but stopped.
Now its back and I didn't move it. There is no air tube connected to the power head.

 

[SaltyDr]

Do you see a vortex being created? Try moving the PH down a little, away from the surface and see if that fixes things.

 

[spleify]

Does it just do it every once in a while or is it a constant thing?

My theory on the occasional spit, as this happens to me, I think tiny microbubbles build up in a pocket at the top of the pump untill all those microbubbles build up and become a bubble that is big enough to get sucked out.

 

[kraze3]

Is it possible those bubbles are coming from somewhere else, like your skimmer?

 

[waynem]

Its cavitation, think boat prop

Only two ways to fix, (ok 3 redesign the prop) reduce the speed, increase the water pressure ie put it lower in your tank.

 

[flameangel9]

Every 3 to 4 seconds it spits bubbles the tank is full. The skimmer puts large bubbles into the tank from the return. It is located a solid foot away from the powerhead but niether one of these has moved.

Heres a photo, power head is in left corner, protien skimmer return is in middle to the right of zoa colony. In pic no bubbles, last 2 days many bubbles. Water level is not in the equation I top off daily.

 

[returnofsid]

If you watch closely, just before it spits out bubbles, you'll see it create a vortex (funnel) above the power head. When this happens, it's getting air from the surface. Most it a lil' lower in the tank. On the power head, there should be an area where the "slits" are kind of blocked. Make sure this is the portion of the "grating" that's above the prop, towards the surface.

 

[reefscape15]

I agree with the vortex if it's happening every few seconds. I personally think it's kind of cool when every minute or so there is a small burst of bubbles into my tank, but every few seconds could get pretty annoying.

 

[iamwrasseman]

i have the same pumps and two of them do that also .no vortex , could air be in the plug cord ? i know it sounds crazy but they have a shieth over the cord so there may be an airway there .the shieth goes all the way down to the plug .

 

[bradbmbj]

<a href=showthread.php?s=&postid=14701229#post14701229 target=_blank>Originally posted</a> by waynem
Its cavitation, think boat prop

Only two ways to fix, (ok 3 redesign the prop) reduce the speed, increase the water pressure ie put it lower in your tank.

I have to agree here, while I do not understand the full dynamics of this, this is a real occurrence. The process operators in refineries have problems with this occasionally,of course these are much larger pumps with different designs, but the principle is the same, I found this article http://en.wikipedia.org/wiki/Cavitation