Be aware that the threads on the plastic cap are very easy to cross-thread when you go for the reinstall. I have to carefully spin mine backwards ("open" direction) while gently pressing down, when I feel it "drop", continue pressing down and begin spinning the "close" direction. If it is crossthreading you will feel extra resistance almost right away. If you get a couple of easy turns, then you're doing it right. Be careful, but you'll be glad you did it yourself, and carry a spare on any long trips!