Before assembling or disassembling the water tank, make sure there is no water in the tank. When assembling the water tank to the main unit, press the water tank down firmly to ensure that the connector of the tank is totally inserted into the bottom of the water tank. When disassembling, hold firmly the base of the main unit and gently pull the tank away from the main unit (tips: pull the tank up and the main unit down). Do it little by little until the main unit is detached from the tank. Be very gentle in order to avoid damages.