2- Water quality :
Water quality is a crucial factor in the taste of a cup of coffee, as it makes up more than 98% of the coffee grounds. Water is an excellent solvent (especially hot water) because it can dissolve most types of particles. Pure water reacts differently with the solid parts of the coffee grounds than impure water (simply put, the particles that make the water hard, dry, or tasteless).
Generally, if water tastes good without any additives, it's good for making coffee. Unfortunately, this isn't always the case. The total dissolved solids (TDS) in the water affect the coffee extraction process and should be within an acceptable range. Some expensive bottled water with very low TDS content can make coffee tasteless, and tap water can be hard and negatively impact the flavor. Using bottled or filtered water is recommended for making good coffee. That's why specialty coffee shops take great care to ensure the quality of the water they use.
