Fluval 406 Cavitating With No Discernible Blockage

Bbunkie01

Hello, all.

I have a Fluval 406 and a Fluval 306 on a 75 gallon hI tech tank.

After recently cleaning the 406, it has been periodically spitting bubbles. You can hear the impeller groan as it chews up an air pocket. This happens approximately 5 or 6 times throughout the day.

I’m assuming this is cavitation due to some kind of back pressure/blockage, but I just can’t find anything.

I’ve taken apart the filter twice now since the first cleaning. No visible blockage. I even took out some of the ceramic rings, thinking the baskets could have been too densely packed. Filter still periodically spitting air.

Some important details to consider:

Filter flow order, in order of what the water flows through first:

1. Side vertical coarse sponges.
2. First Basket: coarse sponge, then fine sponge.
3. Basket: ceramic rings to the brim
4. Basket: ceramic rings and Biostars to the brim
5. Last Basket: a few more ceramic rings, Purigen on top

I have a DIY PVC spray bar for an outflow. Approximately 13 inches in length, 1/2 inch diameter, about a dozen or so holes. I’ve had this spray bar from the beginning, and it has not given me issues before.

I have re-lubed the gasket with petroleum jelly. No visible damage. No visible damage to impeller.

I’m plum out of answers at this point. The bottom basket is somewhat packed with coarse sponge followed by fine sponge. Could this be my problem area?

Lastly, I do inject a high volume of CO2 (7+ bubbles per second) through an inline atomizer on the outflow. This has not given me issues before.

Right now, I have restricted the flow with the flow valve to approximately 75% power. This has helped the issue somewhat, though not entirely. This does lead me to believe it’s a cavitation issue, not a cracked intake hose or gasket problem.

Again, I have not had issues with this filter before the recent cleaning. Ran for weeks without a single air burst.

Any and all help appreciated.
 

leftswerve

Air/gas has to be getting in somehow for it to cavitate. A clog anywhere from the intake strainer to the first vertical sponge will case it to suck air from somewhere. After that, the clog causes a flow reduction.
1. Purigen at the top (not causing your air pocket problem) can easily clog the little strainer hole in the last basket. The hole is only 1.5" accross and the bag can be pushed/sucked into it.
2. The intake strainer and or antiflowback ball is clogged.
3. Pin hole in the intake hose.
4. Air pump/Bubbler at the intake.
 

Similar Aquarium Threads

Replies
3
Views
2K
Bbunkie01
Replies
2
Views
2K
BRP
Replies
5
Views
3K
lojack
Replies
28
Views
2K
JDWebb01
Replies
1
Views
661
Cody

Random Great Thread!

New Aquarium Filter Threads

Latest Aquarium Threads

Top Bottom