I always try to kep my water bottles clean and sanitary, treating them to an overnight fill of hot water and two Steradent tablets. However, I noticed an unpleasant taste from my Zipvit-logo'd bottle yesterday so decided to do a soak. Checked it this morning and noticed some black staining around the inside of the moving part of the nozzle, Took it to bits and found this; That black crud will not come off, despite some energetic scrubbing so I can only assume that mould or similar has got into the silicone rubber of the nozzle. And to think, I've been drinking through that!!