The water filter reduces the hardness of drinking water and protects the boiler from limescale. The filter is also designed to prevent corrosion in the boiler. Furthermore, the filter removes impurities, odors, and unpleasant tastes (such as chlorides) from the water, thereby improving its taste. You'll notice this, for example, in a better tea flavor. The total capacity is 2150 liters at a hardness of 10dH. With average consumption, this is sufficient for replacement once a year. If the Selsiuz boiler is installed with a mixing set, the filter will need to be replaced twice a year, as this will consume more liters. Note: This filter is the new Selsiuz Premium filter. If you have the previous version of this filter in your kitchen, the new filter will not fit directly onto your existing filter head. In that case, please order 350204.