To prevent limescale from forming in the first place, Polti has created Kalstop, the  natural anti-limescale agent for steamers and steam generator irons.
Kalstop derives from a natural product thus is biodegradable and nontoxic.
Kalstop is made of tannate, reducing oxygen in the water, protecting against scale and corrosion, and protecting the metallic walls.

Instructions:

Break open the phial and pour the content into the boiler of Vaporetto
and Vaporella, previously filled with water. Stronger solutions can be used (e.g. 1 phial per litre of water) if the water is particularly hard. For the models
with self-filling feature, we suggest to dilute the phial in 5 litres of water before
pouring it in the tank.