Calgon 3in1 Tablets softens hard water, preventing against limescale, residue and odour. Calgon's leading formulation with active ingredients; polycarboxylates, softens hard water, preventing limescale from forming in the first place. Calgon is not a descaler, but purely a preventative measure - meaning the sooner you introduce Calgon into your daily wash routine, the better! Calgon Tablets begins acting immediately to neutralise limescale, prevent dirt residue and odours leaving your washing machine healthy and your clothes protected.