A water pretreatment system connected to a water supply pipe for supplying water that has been preheated to a home appliance, including: a mixing valve having an inlet connected to the water supply pipe, and a pair of outlets; a water filter having an inlet communicated with one of the pair of outlets of the mixing valve, and having an outlet communicated with the home appliance; a bypass line having an inlet end connected to the other of the pair of outlets of the mixing valve, and having an outlet end connected to the home appliance, the mixing valve being configured to at least one of direct water to the water filter or direct water to the bypass line; and a controller configured to control the mixing valve such that preheated water supplied to the home appliance is one of unfiltered, mixed, or fully filtered by the water filter.