Summarize this article in one sentence.
Using cold, filtered water matters! Unfiltered water won’t taste good, distilled water can ruin your machine, and hard water can accumulate lime in your machine. Using about 14 grams of ground coffee is the amount your espresso machine needs to produce a single cup of strong ristretto.

Summary:
Fill the espresso machine’s reservoir with cold, filtered water. Place 14 grams of the ground coffee in the filter.