i started to notice that when i cleaned the inside of the lid, it did not seem clean. when i pulled out the gasket, it was not clean. i tried to scrub it and then to soak it, but it wasn't coming clean. i wondered if it was possible to just buy a new gasket... and it is!
just thought i'd pass on this tip...in case at some point anyone could use a replacement. the website says that it might be a good idea to replace the gasket if the bottle leaks or drinks are getting residual taste from past drinks. i am so happy when i am able to make a tiny repair instead of having to replace an entire item. from now on, i'm going to wash out my bottle daily and leave it to dry overnight...and hopefully i won't have this issue again.