After 106 batches in 5+ years I've had some trouble in the last year with the pump not pumping, sometimes in the middle of a brew. The first time this happened I took it apart and cleaned it carefully. The pump seemed to be better for a while. Then it started acting up again. This time I was determined to figure out the root cause. Long story short, the magnetic impeller sits on a fixed plastic axle. Over time, the impeller gets enough sticky bits to impede start-up. PBW after every brew for thirty minutes is not enough to clean it. I took some concentrated cleaner and Q-tips (which make a nice interference fit in the impeller shaft) to completely clean the impeller. It should rotate freely on its axle. If there's any stickiness you will eventually have the pump stop working. I suspect this will need to be done every 25 or so batches. Hope this helps someone!