I usually don't post to these things but I had to! You are not the first person I've heard to explain how to brew tea and say either to not boil it or use fresh water because the oxygen escapes. I'm sure that's what you were taught or heard along the way but it is false! Oxygen cannot escape water by boiling, it takes electrical current to remove the oxygen from H2O. What escapes is steam, which is a gaseous state of water. The molecule stays intact as H2O. There is not less oxygen but less water only in the kettle as some evaporates. Just an FYI for you.