Key Features: Smart Functions: Enjoy full control of your kettle through your smartphone by connecting it to the free VeSync app. With VeSync, you can ?Adjust your kettle's temperature ?Change the Hold Temp time ?Schedule when you want your water to boil ?Customize your own preset using the "MyBrew" function · 4 precise temperature presets · 100% 304 food-grade stainless steel · Rapid boil in 3-5 mins Hard water is water that contains calcium or magnesium mineral ions often in the form of carbonate. These ions do not pose any health threat. How should we descale? 1. Fill the kettle with 1 cup of vinegar or lemon juice and 2 cups of water. 2. Boiling the liquids and leave it for 2 hours. 3. Rinse the kettle with clean water, and dry with a soft, clean cloth. 4. Repeat as needed. Notes: 1. Add at least 118 mL of filtered water to the kettle. Do not fill above the 'MAX' line. Wipe any water from the outside of the kettle and the base. 2.It's normal if your kettle exposes spot or rust on the stainless steel bottom after the first use if the water quality in your area is so hard. 3. The kettle will stop heating once the kettle is lifted during heating.