9005 knocking

[Capt_Cully]

I've got a 9005 DOC skimmer, it's been around for a couple of years. It's making a knocking noise almost constantly, but it does occaisionally go away. Still seems to be working fairly well.

Suggestions? Parts to check/replace?

thanks

 

[rvitko]

There are two possible culprits. The motor could be in need of some work or it could be air bubbles popping inside the unit. Take out the pump and check it over thoroughly look for any worn, loose or damaged parts. I have also heard from users that they can get a sound of large breaking bubbles but I have not been able to duplicate this. I would suspect that causes could include a dirty venturi leading to bigger bubbles or being submerged less than normally.

 

[Capt_Cully]

It's definitely mechanical IMO. But, it is in the most violent portion of my sump. I'll try running it in more serene water to see if it still knocks.