Add 1 liter of water (higher than the surface of the dirt) into the inner tank of the main unit, add 2 tablespoons of cleaning agent (citric acid), do not cover the head assembly, turn on the power and boil the water for 30 minutes, pour out the water, rinse with clean water, or add an appropriate amount of white vinegar to the inner tank instead of citric acid, soak the scale for ten minutes (the longer the soaking time, the better the effect).
By vevor