Abstract: A water tank assembly includes a main water tank and an auxiliary water tank. A water pumping device in operation pumps and discharges water in a first water storage space of the main water tank into a second water storage space of the auxiliary water tank. A water guiding device in operation outputs water from the second water storage space to a preset position. The water pumping device in operation can supply water to the auxiliary water tank as needed. The main water tank does not discharge water into the auxiliary water tank when the water pumping device is not in operation. As a result, the water amount in the auxiliary water tank no longer increases.