Microbubbles

I'm having a microbubble problem with my tank. The microbubbles are
coming out of the return spray bar. It's not real bad, I can still see
in the tank fine, I was just wanting it crystal clear. The tank is a
85 gallon drilled Oceanic, 2-1" holes drain to the ~30g sump below,
with a Iwaki MD40RLXT pump return. The output from the pump has a Y
split, one goes directly to the tank through a pvc spray bar, the other
feeds back to the sump and has a ball valve on it to adjust the flow.
It looks like there are no microbubbles entering the pump. I mentioned
this to some people at work, wondering how in the world I could be
getting these bubbles, and one person mentioned that it could possible
come from cavitation. I didn't even think of this, but it sounds like
he might be right. Cavitation will cause the microbubbles right? If
my pipe leading from the sump to the pump is smaller than what the pump
calls for I think it will cause cavitation. The pump sounds fine, and
seems to be working perfectly except that I'm seeing this bubble
problem. Has anybody here experienced a problem with cavitation
before? This is a new setup, has been running for 6-8 weeks, and I am
using 1" pvc (i think thats outside diameter) to the tank, and 1" spa
hose/pvc back to the sump.

And I just noticed that I have a 90degree elbow right before the intake
of my pump, I heard that could cause the problem..

As I have read in other posts, 90 degree turns before the pump can
cause cavitation (microbubbles). I took it out yesterday and have a
straight pipe leading to the pump. No bubbles now at all. Just an
update if anyone else has this problem.

Yep it was cavitation.

Wayne Sallee
Wayne's Pets



nacree wrote on 12/2/2006 11:01 AM:
As I have read in other posts, 90 degree turns before the pump can
cause cavitation (microbubbles). I took it out yesterday and have a
straight pipe leading to the pump. No bubbles now at all. Just an
update if anyone else has this problem.