Water
The quality of the water used is very important for the preparation of a good espresso. It is important not to use hard water, so the taste and the aroma of the ground beans can fully unfold.
The water hardness varies from region to region, depending on the potassium salts solved in it. A German hardness grade (°dh) complies with the content of 0.35 oz limestone per 264.17 gallons of water. Many water filter manufacturers offer test cards, helping you to find out about the composition of your tap water and what hardness grade it is. We recommend a hardness grade from about 6 °dh (US: 0.336 ppm CaCO₃) A normal water filter filters the limestone out of the water, so that the aroma of the espresso can unfold fully.
Apart from the taste, there is also another reason why you should not use hard water. Limescale can cause crust formation in the pipes and the boiler and thus cause slow water flow. Limescale blockage can also cause a reduction in temperature of the outflowing water and thus affect the outcome.