I can't seem to get my whisper powerfilter (junior, small size, I can't remember, but it uses junior size cartriges) to start pumping water. It makes noise, and shakes a little when I move the intake up and down, but I can't get it to start pumping. I've had this problem before, and solved it only through blind luck. I can't seem to get it to work this time. Is there a trick to it? I'd appreciate any help whatsoever. Thank you very much.



