Designed specifically for 4 and 5 Series Venta Airwashers, the Venta Water Treatment Additive improves the performance of the unit by preventing mineral deposits. Our Water Treatment Additive (WTA) is specially formulated to maintain hygienic conditions in the Lower Housing of your Venta Airwasher by preventing calcium and lime build up. This WTA creates a sheeting action on the Disc Stack to maximize the surface area coated with water, which aids in the evaporation process. There is no need to add Venta Water Treatment Additive to your Airwasher each time you add water, as the ingredients do not evaporate. Simply add Venta WTA to your Airwasher after cleaning every 10 to 14 days.