GarmentCare Guide 
The iron-descaling reference explains that limescale can affect steam delivery and leave unwanted marks on clothing. The reservoir and internal passages are different from the external soleplate. Cleaning one does not necessarily resolve deposits in the other.
Follow the manufacturer's descaling process and recommended water or treatment. Do not assume vinegar is allowed simply because it works in a kettle. Regular checks of steam performance and the appliance instructions provide a clearer maintenance plan than waiting for visible residue on a garment.
