I pulled this info from the manual. I am including a pic and the link. Hopefully this is helpful.
If you do not want to use the CLEARYL filter cartridge Blue, you will need to set the water hardness. The following water hardness settings are available: Water hardness Symbol(s) shown in display Level 1: 1-15 °dH 1 symbol illuminated Y Level 2: 16-23 °dH 2 symbols illuminated Y < Level 3: 24-30 °dH 3 symbols illuminated Y < > & T Touch the Descaling symbol. The Y, < and & symbols light up. T Touch the Y, < or > symbol to set the water hardness, e.g. symbol Y for 'level 1'. The Y and & symbols light up. & T Touch the Descaling symbol. The Water Tank symbol M lights up. T Place a receptacle under the coffee spout. T Remove the water tank. T Fill the water tank with fresh, cold water and reinsert it. The Y, < and > symbols flash. The system fills with water and the water flows directly into the drip tray. The operation stops automatically. The machine heats up. The Y, < and > symbols flash. The machine is rinsed, water flows out of the coffee spout. The rinse stops automatically. The Ristretto Y, Espresso < and Coffee > symbols and the symbol for 'strong' coffee strength _ light up. Your ENA is ready for use.