You should switch to using the cold water tap to fill your kettle! Also, when you see what kind of build up can happen in a hot water heater, you'll definitely want to avoid drinking from the hot water tap.
Yes, I didn't say it was lead. It is just a dirty, unpleasant container. Not where you want to get your drinking water, especially for tea.
It isn't just limescale in your hot water heater, it is whatever your water pipe carries in and accumulates in the tank. We lived at the beach and had to flush sand out every couple years.
It is potentially a decade of accumulated junk in the hot water heater. If you aren't able to taste the difference, the data backs up the issue with drinking hot water.
https://www.youtube.com/watch?v=kAzKts6Wp1Q&t=207s