What is the best water for espresso machines?

Water makes up over 98% of your espresso, so its quality is just as important as the quality of your coffee beans. Espresso machines are particularly sensitive to water chemistry because they use high pressure and heat to extract coffee. If your water is too hard—meaning it has high levels of calcium and magnesium—it will cause scale to build up inside the boiler and pipes, eventually clogging the machine and ruining the heating elements.

On the other hand, if your water is too soft or distilled, it can be just as problematic. Water needs a certain amount of mineral content to interact with the coffee grounds and extract flavor. Pure, distilled water can actually be corrosive to the metal components of your machine, leaching minerals from the boiler itself. The goal is to find a balance: water that is clean and free of chlorine or off-flavors, but contains enough minerals to facilitate a great extraction.

Many specialty coffee shops use water filtration systems that remove impurities while adding back a precise blend of minerals. For the home user, a high-quality carbon filter or a reverse osmosis system with a remineralization stage is often the best solution. You can also purchase water test kits to check your tap water's hardness and alkalinity. If your tap water is very hard, using a pitcher-style filter or a dedicated espresso machine water filter can help, but it may not be enough to prevent scale entirely.

In practice, the best approach is to use water that tastes good on its own. If your tap water has a strong chlorine smell or tastes metallic, your espresso will likely taste the same. By investing in a good filtration system, you not only improve the flavor of your coffee but also extend the lifespan of your espresso machine. It is a small investment that pays off in both better shots and fewer maintenance headaches.