Water temperature can play a role in how coffee tastes. There is a reason that Cold Brew tastes so smooth - it’s never heated.
If you use water that is too hot - over 205 degrees - it can leave your coffee bitter.
We recommend between 195 and 205 degrees. If your cup is bitter try taking it down to 195. Unfortunately, with automatic drip and espresso machines, you don’t have much control of this.
If you do not have an electric kettle that you can set the temperature - take the water off the boil and then let it sit for 30 seconds up to 2 minutes before pouring.
If this doesn't change the bitterness check out these other reasons for a sour cup: