Contaminants in the water prior to filtering:If the water already contained contaminants that were not completely removed by the activated carbon filter, these contaminants may have become concentrated during the boiling process, leading to residues.

Overloading of the filter:If the activated carbon filter is overloaded, it may not be able to remove all contaminants effectively. This could result in certain contaminants, such as limescale, remaining in higher concentrations in the water and depositing during boiling.

Inadequate filter maintenance:Activated carbon filters must be regularly maintained and replaced to maintain their effectiveness. If the filter has not been properly maintained, its performance may decline over time, which can lead to inadequate removal of impurities.

Boiling process:In some cases, residues may be produced by the boiling process itself, particularly when the water has evaporated significantly and mineral residues are left behind.

Filters mineralise: Theyonlyfilterout pollutants – essential minerals remain in the water

It is important to note that activated carbon filters cannot remove all contaminants 100 per cent, and their effectiveness may vary depending on the specific contaminants present in the water. In some cases, it may therefore be advisable to consider additional water treatment methods