Venta Airwasher Water Treatment Additive - 2 Pack The venta water treatment additive is designed for the venta air washer models It creates a sheeting action on the disks to maximize the surface area coated in water - this aids in the evaporation process The water treatment additive also helps prevent calcium and lime build-up They remain in the unit until poured out for cleaning (approximately every 10 to 14 days) Maintain hygienic conditions in the lower housing and to improve the evaporation process