Last week adult DD was at her dad's house, and her stepmother went to make tea. She just opened the kettle and checked there was water, then set it to heat. DD was
and said "Don't you fill it with fresh water first? to which stepmother took the hump and said no, you just top up with more water as needed.
Now, in my house, I heat as much as I think I need and pour any excess out, so the kettle is filled with fresh water each time.
Obviously my wonderful DD knows that my way is the right way
, but what do you lot think?