Should I use filtered water for my coffee machine?

Water is the most overlooked ingredient in coffee brewing. Because a cup of coffee is almost entirely water, the mineral content and purity of that water act as the canvas upon which the coffee's flavors are painted. If your water is too hard, it can lead to excessive extraction, making the coffee taste bitter or chalky. If it is too soft, it may fail to extract the necessary compounds, resulting in a flat or sour cup.

Beyond flavor, the health of your coffee machine is at stake. Tap water often contains high levels of calcium and magnesium, which, when heated, precipitate out of the water and form scale (limescale) inside your machine's boiler, pipes, and heating elements. This scale acts as an insulator, preventing the machine from reaching the correct brewing temperature and eventually clogging the delicate flow paths. Over time, this can lead to a complete failure of the machine.

Using a water filter—whether it is a simple pitcher filter, an in-tank cartridge, or a more advanced reverse osmosis system—helps to balance the mineral content and remove impurities like chlorine, which can impart an unpleasant chemical taste to your coffee. The goal is not to remove all minerals, as some are necessary for flavor extraction, but to achieve a 'balanced' water profile that is safe for your machine and beneficial for your coffee.

In practice, you should aim for water that is clean, odorless, and has a moderate level of hardness. If you are unsure about your water quality, many specialty coffee shops sell water test kits or even pre-formulated mineral packets that you can add to distilled water to create the 'perfect' brewing water. By taking control of your water, you are taking one of the most effective steps toward improving the quality of your home-brewed coffee and extending the lifespan of your equipment.