Water purification device, flushing control method for water purification device, and water purification system

A water purification device, comprising:

• an ultrafiltration composite filter element, provided with a plurality of filter elements connected in parallel, wherein each of the plurality of filter elements is provided with at least one water inlet and at least one purified water outlet, and purified water outlets of the plurality of filter elements communicate with each other;
• and
• an opening/closing unit, communicating with water inlets of the plurality of filter elements, wherein
• the opening/closing unit, when in a water-producing state, is configured to introduce raw water into the plurality of filter elements from the water inlets, and discharge purified water by the purified water outlets after filtration of the plurality of filter elements;
• and the opening/closing unit is further configured to switch from the water-producing state to a flushing state, and, when in the flushing state, introduce the raw water into the plurality of filter elements from water inlet(s) of one or more filter elements in the plurality of filter elements;
• and in this case, the purified water outlets of the plurality of filter elements are closed and communicate with each other, an other one or more filter elements in the plurality of filter elements are flushed with purified water, and then waste water is discharged by water inlet(s) of the other one or more filter elements or a drainage outlet.