You generally have to dispose of the drain water once a week. However, this is the standard frequency of a new unit that is operated 8 hours a day at 35°C air temperature and 60% humidity. Therefore, the real frequency with which you have to empty the drain tank can vary significantly depending on the conditions where and how much you use the unit. To be on the safe side we recommend you to empty the drain tank every day after you have finished using the unit.