Are you a coffee perfectionist?
If so, know this.
Brewed coffee is acidic and when done, it should have a pH around 5.0.
The best water to use for coffee should have a pH that is neutral, around 7.0.
Municipal water is frequently alkaline, i.e., of a pH greater than 7.0, to prevent corrosion of pipes.
To acidify your coffee water, i.e., lower the pH from greater than 7.0 to 7.0, add pinches of tartaric acid, aka cream of tartar, until the water tastes slightly tart.
Or you can get a pH meter to measure the pH. (That is known as overkill. Although, if you are a coffee nut...)
Do not add steak tartare. It will not work.