Answer

To remove the tube from the reservoir (or to take off the bite valve), soak the end of the reservoir with the tube connection in hot water for 5 to 10 minutes. This should soften the plastic and make it easier to pull the tube off. You can use the same trick to reattach the tube or bite valve: soak everything in warm water before pushing the parts back together. Once the plastic cools, it will firm up and seal itself more securely.