I have a used eheim 2215 I want to use for a polishing filter. Anyways, I went to test it and the pump runs but it won't push any water. It will just a little bit but only when it's on it's side.
I'm guessing either the impeller is bad or I'm doing something wrong on startup. I filled the canister full with water and submerged the pickup. Anything else that needs to be done? 

