What is scale? Scale in water forms as a natural process. As rain falls, it picks up CO2, making the water slightly acidic, effectively becoming a natural solvent. As the rainwater seeps to underground aquifers, it dissolves minerals, thereby becoming “hard.” Hard water is generally concentrated with four hard minerals: calcium, magnesium, carbonate, and sulfate. Every water supply has some dissolved mineral content. How does scale form in my coffee maker? When energy (heat from heating element) is applied to hard water, the minerals “drop out” of the water and settle on surfaces…most commonly referred to as limescale. These minerals can form a hard crust that can cause many problems with equipment, from clogging to increased energy requirements and ultimately even failure of the coffee maker. Since all tap water contains some level of mineral deposits. To learn more about water hardness, including information specific to your region of the country, please click on the link below to the United States Geological Survey site.