What effect does poor water quality have on espresso?

Poor water quality significantly impacts the overall quality of espresso, and this is primarily why it leads to a bad espresso brew. Water is the main ingredient in espresso, comprising approximately 90% of the beverage. Therefore, impurities and poor mineral content in the water can adversely affect the extraction process.

When water is of low quality, it might contain undesirable substances such as chlorine, heavy metals, or excessive hardness, affecting the taste and extraction. This can lead to an imbalanced flavor profile—often resulting in over-extraction or under-extraction, which can produce espresso that is either overly bitter and harsh or weak and sour.

Additionally, poor water quality can introduce off-flavors, disrupt the emulsion of oils, and negatively impact the crema formation. Crema is the golden layer that forms on top of a well-pulled espresso shot, vital for both texture and flavor. Thus, poor water quality directly correlates with a subpar espresso experience, confirming that it results in bad espresso brew.