Hiya, we moved house yesterday morning and set up the canister filter in the afternoon. It;s an Eheim pro 2 and all functioning fine, but it occasionally starts whistling! Anybody had this before? What's the possible cause? I thought maybe air trapped in the unit so i did the old tilt and rock it back and forth trick, some air did come out, but it hasn't sorted out the whistling. I switched it off, waited a minute then switched it back on, restarted just fine, but still whistling. Checked the canister and pipes and no water leaking so probably not a small crack or leak either.
When we woke up this morning it's still doing the occasional whistle, roughly as often and persistent as it was yesterday.
Any suggestions?