The water filter reduces rush and mineral contaminants from entering the system which helps prolong the life of the steam generator. Although SteamSpa generators have a built-in auto-drain, which purges all fluids from the system when not in use, the remaining droplets of water which remain can lead to the formation of limescale and other mineral deposits. These depots restrict water flow, as well as limit the efficiency of the heating elelemtns. The water filter prevents the formation of limescale deposits and prolongs the life of your steam generator, which also improves the quality and quantity of steam.